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<title>Cross Connection Control Manual</title>
<type>single page tiff</type>
<keyword>water backflow pressure valve cross connection check supply potable system preventer hose test device plumbing figure connections devices vacuum shut</keyword>
<author>Hendrickson, Howard D.  United States. Environmental Protection Agency. Office of Drinking Water. United States. Environmental Protection Agency. Office of Drinking Water.</author>
<publisher>U.S. Environmental Protection Agency, Office of Water, Office of Drinking Water,</publisher>
<subject>Plumbing; Water pipelines; Water supply; Water pollution; Manuals; Connectors; Public health; Hazards; Installing; Water distribution; Distribution systems; Test methods; Prevention; Drinking water; Backflow Sanitary Engineering ; Water Supply ; Water Pollution--prevention</subject>
<abstract>Plumbing cross-connections, which are defined as actual or potential connections between a potable and non-potable water supply, constitute a serious public health hazard. There are numerous, well-documented cases where cross-connections have been responsible for contamination of drinking water, and have resulted in the spread of disease. The Manual has been designed as a tool for health officials, waterworks personnel, plumbers, and any others involved directly or indirectly in water supply distribution systems.  </abstract>

v>EPA        Cross-Connection
                Control Manual
                United States
                Environmental Protection Agency
                Office of Water
                Office of Drinking Water
                First Printing 1973
                Reprinted 1974, 1975
                Revised 1989

   Plumbing crossicphnections,
    whichare d,elinedras, actual
or potential connections
between a potable and
non-potable water supply,
constitute a serious public
health hazard. There are
numerous, well-documented
cases where
cross-connections have been
responsible for contamination
of drinking water, and have
resulted in the spread  of
disease. The problem is a
dynamic one,  because  piping
systems are continually being
installed, altered, or
  Control of
cross-connections is possible,
but only through thorough
knowledge and vigilance.
Education  is essential, for
even those who are
experienced in piping
installations fail to recognize
cross-connection possibilities
and dangers. All
municipalities with public
water supply systems should
have cross-connection control
programs. Those responsible
for institution?! or private
water supp?'   should also be
familiar v/if   a dangers of
cross-cormt,    ns and should
exercise care   1 surveillance
of their syste   s.
  This Cross-  Connection
Control Man  al has been
designed as   tool for health
officials, we erworks
personnel, paimbers, and any
others involved directly or
indirectly in water supply
distribution systems. It is
intended to be used for
educational, administrative,
and technical reference in
conducting cross-connection
control programs. This
manual is  a revision of an
earlier book entitled Water
Supply and Plumbing
Cross-Connections (PHS
Publication Number 957),
which was produced under
the direction of Floyd B.
Taylor by Marvin T. Skodje,
who wrote the text and
designed the illustrations.
Many of the original
illustrations and text have
been retained in this edition.
Previous revisions were done
by Peter C. Karalekas, Jr. with
guidance from Roger D. Lee
incorporating suggestions
made by the staff of the EPA
Water Supply Division, other
governmental agencies, and
interested individuals.
  This 3rd edition was
produced as a result of an
updated need for
cross-connection control
reference material reflecting
an increase in
cross-connection control
activity throughout the
United States. It has been
revised and re-issued
reflecting a demand for its
use, together with requests
for a document that covers
the broad spectrum of
cross-connection control from
both the basic hydraulic
concepts through the
inclusion of a sample
program that can be a  guide
for a program at the
municipal level. New
backflow devices have been
included in this revision that
are now being produced by
manufacturers reflecting the
needs of the market. Updated
actual cross-connection case
histories have been added
containing graphic schematic
illustrations showing how the
incidents occurred and how
cross-connection control
practices could be applied  to
eliminate future
re-occurrence. A more
detailed explanation of
cross-connection control
"containment" practice has
been included together with
the use for "internal backflow
protective devices" and
"fixture outlet protection".
  This new edition was
prepared by Howard D.
Hendrickson, PE, vice
president of Water Service
Consultants, with assistance
from Peter C. Karalekas, Jr. of
Region 1, EPA, Boston.
American Water Works Association Policy on
Cross-Connections	iv


1. Purpose & Scope	1
2. Public Health Significance of Cross-Connections	2
3. Theory of Backflow and Backsiphonage	12
4. Methods and Devices for the Prevention of
  Backflow and Backsiphonage  	16
5. Testing Procedures for Backflow Preventers	25
6. Administration of a Cross-Connection Control Program 30
7. Cross-Connection Control Ordinance Provisions  	33


A. Partial list of plumbing hazards	38
B. Illustrations of backsiphonage	38
C. Illustrations of backflow	40
D. Illustrations of air gaps	41
E. Illustrations of vacuum breakers	41
F. Glossary	42
G. Bibliography	43
H. Sample cross-connection survey form   	44
I. Sample cross-connection test form	45


 Human blood in the water system	2
 Burned in the shower  	  3
 Heating system anti-freeze into potable water  ..     	  3
 Salty drinks  	   4
 Paraquat in the water system	  4
 Propane gas in the water mains  	   5
 Chlordane  and heptachlor at the Housing Authority  	  5
 Boiler water enters high school drinking water	6
 Pesticide in drinking water  	  6
 Car wash water in the water main  	  7
 Shipyard backflow contamination  	  7
 Chlordane  in the water main	  8
 Hexavalent chromium in drinking water 	     8
 Employee health  problems due to cross-connection  	  9
 Dialysis machine contamination	  10
 Creosote in the water mains	  11
 Kool aid laced with chlordane 	  11
   1  Pressure  exerted by one foot of water at sea level .... 12
   2  Pressure  exerted by two feet of water at sea level ...  13
   3  Pressure  on the free surface of a liquid at sea level   . 13
   4  Effect of  evacuating air from a column   	13
   5  Pressure  relationships in a continuous
     fluid system at the same elevation  	   13
   6  Pressure  relationships in a continuous
     fluid system at different elevations 	      	   14
   7  Backsiphonage in a plumbing system   	14
   8  Negative pressure created by constricted flow  	  14
   9  Dynamically  reduced pipe pressure(s).     	14
 10  Valved connection between potable water and
     nonpotable fluid 	     	      	15
 11  Valved connection between potable water
     and sanitary  sewer  	15
 12  Air gap	16
 13  Air gap in a piping system	16
 14  Barometric loop	17
 15  Atmospheric vacuum breaker  	     	17
 16  Atmospheric vacuum breaker typical installation .... 17
 17  Atmospheric vacuum breaker
      in plumbing suppK system	17
 18  Hose bibb vacuum breaker	18
 19  Typical installation of hose bibb  vacuum breaker ...  18
 20  Pressure  vacuum breaker . .     	   18
 21  Typical agricultural and industrial application of
     pressure vacuum breaker 	  19
22   Double check valve with atmospheric vent	19
23   Residential use of double check with atmospheric vent 19
24   Double check valve	19
25   Double check valve detector check  	  20
26   Residential dual check	20
27   Residential installation  	20
28   Copper horn 	20
29a  Reduced pressure zone backtlow preventer	 21
29b  Reduced pressure zone backflow preventer	21
30   Reduced pressure zone backflow preventer—
     principle ol  operation	22
31   Plating plant installation	22
32   Car wash installation 	22
33   Typical by-pass configuration, reduced pressure
     principle devices	23
34   Typical installation,  reduced  pressure principle
     device, horizontal illustration  	23
35   Typical installation,  reduced  pressure principle
     device, vertical installation 	23
36   Typical installation,  double check valve,
     horizontal and vertical installation  	24
37   Typical installation,  residential dual check
     with straight set and copper horn 	24
38   Pressure vacuum breaker  	26
39   Reduced pressure principle backflow preventer. Step 1 27
40   Reduced pressure principle backflow preventer, Step 2 27
41   Double check valve assemblies, Method 1 	28
42   Double check valve assemblies, Method 2	 29
43   Cross-connection protection,  commercial,
     industrial and residential	30
44   Backsiphonage, Case 1 	38
45   Backsiphonage, Case 2	38
46   Backsiphonage, Case 3	 39
47   Backsiphonage, Case 4	39
48   Backsiphonage, Case 5	39
49   Backsiphonage, Case 6	39
50   Backflow Case 1  	40
51   Backflow Case 2  	40
52   Backflow Case 3  	40
53   Backflow Case 4  	40
54   Air gap to sewer subject to backpressure—force main 41
55   Air gap to sewer subject to backpressure—gravity drain 41
56   Fire system makeup tank for  a dual water system  .... 41
57   Vacuum breakers	41
58   Vacuum breaker arrangement for an outside
     hose hydrant    	41

Statement  of  Policy
on Public Water  Supply  Matters.
Cross Connections (Adopted
by the Board of Directors on
Jan. 26,1970, and revised on
June 24, 1979, and reaffirmed
June 10, 1984)
The American Water Works
Association recognizes that
the water purveyor has a
responsibility to provide its
customers at the service
connection with water that is
safe under  all foreseeable
circumstances. Thus, in the
exercise of  this
responsibility, the water
purveyor must take
reasonable  precaution to
protect the  community
distribution system from the
hazards originating on the
premises of its customers that
may degrade the water in the
community distribution
  Cross-connection control
and plumbing inspections  on
premises of water customers
are regulatory in nature and
should be handled through
the rules, regulations and
recommendations of the
health authority or the
plumbing-code enforcement
agencies having jurisdiction.
The water purveyor,
however, should be aware  of
any situation requiring
inspection  and/or
reinspection necessary to
detect hazardous conditions
resulting from
cross-connections. If, in the
opinion of the utility,
effective measures consistent
with the degree  of hazard
have not been taken by the
regulatory agency, the water
purveyor should take such
measures as he may deem
necessary to ensure that the
community distribution
system is protected from
contamination. Such action
would include the
installation of a  backflow
prevention device, consistent
with the degree  of hazard at
the service connection or
discontinuance of the service.
  In addition, customer use
of water from the community
distribution system for
cooling  or other purposes
within the customer's system
and later return  of the  water
to the community
distribution system is not
acceptable and is opposed by

Chapter One
and  Scope
   Public health officials have
   long been concerned
about cross-connections and
backflow connections in
plumbing systems and in
public drinking water supply
distribution systems. Such-
cross-connections, which
make possible the
contamination of potable
water, are ever-present
dangers. One example of
what can happen is an
epidemic that occurred  in
Chicago in 1933.  Old,
defective, and improperly -
designed plumbing and
fixtures permitted the
contamination of drinking
water. As a result, 1,409
persons contracted amebic
dysentery; there were 98
deaths. This epidemic, and
others resulting from
contamination introduced
into a water supply through
improper plumbing, made
clear the  responsibility of •
public health officials and
water purveyors for
exercising control over public
water distribution systems
and all plumbing systems
connected to them. This
responsibility includes
advising and instructing
plumbing installers in the
recognition and elimination
of cross-connections.
  Cross-connections are the
links through which it is
possible for contaminating
materials to enter a potable
water supply. The
contaminant enters the
potable water system when
the pressure of the polluted
source exceeds the pressure
of the potable source. The
action may be called
backsiphonage or backflow.
Essentially it is reversal of
the hydraulic gradient that
can be produced by a variety
of circumstances.
  It might be assumed that
steps  for detecting and
eliminating cross-
connections would be
elementary and obvious.
Actually, cross-connections
may appear in  many subtle
forms and in unsuspected
places. Reversal of pressure
in the water may be freakish
and unpredictable. The
probability of contamination
of drinking water through a
cross-connection occurring
within a single plumbing
system may seem remote;
but, considering the
multitude of similar systems,
the probability is great.

Why  do such
cross-connections exist?
First,  plumbing is frequently
installed by persons who are
unaware of the inherent
dangers of cross-connections.
Second, such connections are
made as a simple matter of
convenience without  regard
to the dangerous situation
that might be created. And,
third, they are  made with
reliance on inadequate
protection such as a single
valve or other mechanical
  To combat the dangers of
cross-connections and
backflow connections,
education in their recognition
and prevention is needed.
First,  plumbing installers
must know that hydraulic
and pollutional factors may
combine to produce a
sanitary hazard if a
cross-connection is present.
Second, they must realize
that there  are available
reliable and simple standard
backflow prevention devices
and methods that may be
substituted for the
convenient but dangerous
direct connection. And third,
it should be made clear to all
that the hazards resulting
from direct connections
greatly outweigh the
convenience gained.
  This manual does not
describe all the
cross-connections possible in
piping systems. It does
attempt to reduce the subject
to a statement of the
principles involved and to
make it clear to the reader
that such installations are
potentially dangerous. The
primary purpose is to define,
describe, and illustrate
typical cross-connections and
to suggest simple methods
and devices by which they
may be eliminated without
interfering with the functions
of plumbing or water  supply
distribution systems.

Chapter Two
                                                     Human  Blood in
                                                     the Water System
Public   Health
Significance  of
                             Public health officials have
                             long been aware of the
                          impact that cross-connections
                          play as a threat to the public
                          health. Because plumbing
                          defects are so frequent and
                          the opportunity for
                          contaminants to invade the
                          public drinking water
                          through  cross-connections are
                          so general, enteric infections
                          caused by drinking water
                          may occur at most any
                          location and at any time.
                            The following documented
                          cases of  cross-connection
                          problems illustrate and
                          emphasize how actual
                          cross-connections have
                          compromised the water
                          quality and the public health.
   Health Department officials
   cut off the water supply
to a funeral home located in
a large southern city, after it
was determined that human
blood had contaminated the
fresh water supply. City
water and plumbing officials
said that they did not think
that the blood contamination
had spread beyond the
building, however, inspectors
were sent into the
neighborhood to check  for
possible contamination. The
chief plumbing inspector had
received a telephone call
advising that blood  was
coming from drinking
fountains within the
building. Plumbing  and
county health department
inspectors went to the scene
and found evidence that the
blood had been circulating in
the water system within the
building. They immediately
ordered the building cut off
from the water system at the
  Investigation revealed that
the funeral home had been
using a hydraulic aspirator t
drain fluids from the bodies
of human "remains" as part
of the embalming process.
The aspirator directly
connected to the water
supply  system at a faucet
outlet located on a sink in
the "preparation"
(embalming) room. Water
flow through the aspirator
created suction that was
utilized to draw body fluids
through a hose and needle
attached to the suction side
of the aspirator.
  The contamination of the
funeral  home potable water
supply  was caused by a
combination of low water
pressure in conjunction witl
the simultaneous use of the
aspirator. Instead of the bod;
fluids flowing into the
sanitary drain, they were
drawn in the  opposite
direction—into the potable
water supply of the funeral
                                                                   Normal operation
                                                             Positive supply pressure Potable water
                                                    Negative supply pressure

                                                            Reverse flow through
                                                            aspirator due to
                                                            back siphonage

Burned in the
                              Heating System
                              Anti-Freeze into
                              Potable Water
A    resident of a small town
    in Alabama, jumped in
the shower at 5 a.m. one
morning in October, 1986,
and when he got out his
body was covered with tiny
blisters. "The more I rubbed
it, the worse it got," the 60
year old resident said. "It
looked like someone took a
blow torch and singed me."
  He and several other
residents received medical
treatment at the emergency
room of the local hospital
after the water system was
contaminated with sodium
hydroxide, a strong caustic
  Other residents claimed
that, "It (the water) bubbled
up and looked like Alka
Chemical bulk storage and holding tanks
Seltzer. I stuck my hand
under the faucet and some
blisters came up." One
neighbor's head was covered
with blisters after she washed
her hair and others
complained of burned throats
or mouths after  drinking the
  The incident began after an
8-inch water main, that fed
the town, broke and was
repaired. While  repairing the
water main, one workman
suffered leg burns from a
chemical in the  water and
required medical treatment.
Measurements of the ph of
the water were as high as 13
in some sections of the  pipe.
  Investigation into the cause
of the problem led to a
possible source  of the
contamination from a nearby
chemical company that
distributes chemicals such as
sodium hydroxide. The
sodium hydroxide is brought
to the plant in liquid form in
bulk tanker trucks and is
transferred to a holding tank
and then pumped into 55
gallon drums. When the
water main broke, a truck
driver was adding the water
from the bottom of the tank
truck instead of  the top, and
sodium hydroxide
back-siphoned into the water
                                                 Water mam
                                                 break and
   Bangor Maine Water
   Department employees
discovered poisonous
anti-freeze in a homeowner's
heating system and water
supply in November, 1981.
The incident occurred when
they shut off the service line
to the home  to make repairs.
With the flow of water to the
house cut off, pressure in the
lines in the house dropped
and the anti-freeze, placed in
the heating system to prevent
freeze-up of an unused hot
water heating system,
drained out of the heating
system into house water
lines,  and flowed out to the
street. If it had not been
noticed, it would have
entered the homeowner's
drinking water when the
water pressure was restored.
                                                               Automobile antifreeze
                                                               added to boiler water
                                                                           (reverse flow)
                                                                                 Normal flow

                                                                           Curb stop with stop and waste dram
                                                                          Water main

Salty  Drinks
                              Paraquat in the
                              Water  System
  In January, 1981, a
  nationally known fast food
restaurant located in
southeastern United States,
complained to the  water
department that all their soft
drinks were being rejected by
their customers as  tasting
"salty." This included soda
fountain beverages, coffee,
orange juice, etc. An
investigation revealed that an
adjacent water customer
complained of salty water
occurring simultaneously
with the restaurant incident.
This second complaint came
from a water front  ship repair
facility that was also being
served by the same water
main lateral. The
investigation centered on the
ship repair facility and
revealed the following:
  • A backflow preventer
that had been installed on
the service line to the
shipyard had frozen and had
been replaced with a spool
piece sleeve.
  • The shipyard fire
protection system utilized sea
water that was pumped by
both electric and diesel
driven pumps.
  • The pumps were primed
by potable city water.
  With the potable priming
line left open and the pumps
maintaining pressure in the
fire lines, raw salt  water was
pumped through the priming
lines, through the spool
sleeve piece, to the ship
repair facility and  the
                           Backflow preventer
                           replaced by spool piece
                             Salt water suction line
                             for fire protection
ft\7e\\ow gushy stuff"
   JL poured from some of
the faucets in a small town in
Maryland, and the State of
Maryland placed a ban on
drinking the water supply.
Residents were warned not to
use the water for cooking,
bathing, drinking or any
other purpose except for
flushing toilets.
  The incident drew
widespread attention and
made the local newspapers.
In addition to being the lead
story on the ABC news
affiliate in Washington, D.C.
and virtually all the
newspapers that evening. The
news media contended that
lethal pesticides may have
contaminated the  water
supply and among the
contaminants was paraquat, a
powerful agricultural
  The investigation disclosed
that the water  pressure in the
town water mains was
temporarily reduced due to a
water pump failure  in the
town water supply pumping
system.  Coincidentally, a gate
valve between a herbicide
chemical holding  tank and
the town water supply piping
had been left open. A lethal
cross-connection had been
created that permitted the
herbicide to flow into the
potable water supply system.
Upon restoration of water
pressure, the herbicides
flowed into the many faucets
and outlets on the town
water distribution system.
  This cross-connection
created a needless and costly
event that fortunately did not
result in serious illness or
loss of life. Door-to-door
public notification, extensive
flushing, water sample
analysis, emergency
arrangements to provide
temporary potable water  from
tanker trucks, all contributed
to an expensive and
unnecessary town burden.
                                                            Potable town water
                                                            I	1
                                            Recommended installation of backflow preventer

  Propane Gas in
  the Water Mains
Hose used
         propane tank purging
         cross connected to
         pnvate_fire hydrant
backflow preventer
Water mam
      Hundreds of people were
      evacuated from their
   homes and businesses on an
   August afternoon in a town
   in Connecticut in 1982 as a
   result of propane entering the
   city water supply system.
   Fires were reported in two
   homes and the town water
   supply was contaminated.
   One five-room residence was
   gutted by a blaze resulting
   from propane gas "bubbling
   and hissing"  from a bathroom
   toilet and in another home a
   washing machine explosion
   blew a woman against a wall.
   Residents throughout the area
   reported hissing, bubbling
   noises, coming from washing
   machines, sinks and toilets.
   Faucets sputtered out small
   streams of water mixed with
   gas and residents in the area
   were asked to evacuate their
    This near-disaster occurred
   in one, 30,000 gallon
   capacity liquid propane tank
   when the gas company
   initiated immediate repair
   procedures. To start the
repair, the tank was "purged"
of residual propane by using
water from one of two private
fire hydrants located on the
property. Water purging is
the preferred method of
purging over the use of
carbon dioxide since it is
more positive and will float
out any sludge as well as any
gas vapors. The "purging"
consisted of hooking up a
hose to one of the private  fire
hydrants located on the
 Sroperty and initiating
 ushing procedures.
  Since the vapor pressure of
the propane residual in the
tank was 85 to 90 psi., and
the water pressure was only
65 to 70 psi., propane gas
backpressure backflowed into
the water main. It  was
estimated that the gas flowed
into the water mains for
about  20 minutes and that
about  2,000 cubic feet of gas
was involved. This was
approximately enough gas to
fill  one mile of an 8-inch
water  main.
                             Chlordane and
                             Heptachlor at the
                             Housing Authority
'T'he services to seventy five
 J. apartments housing
approximately three hundred
people were contaminated
with chlordane and
heptachlor in a city in
Pennsylvania, in December,
1980. The insecticides
entered the water supply
system while an
exterminating company was
applying them as a
preventative measure against
termites. While the pesticide
contractor was mixing the
chemicals in a tank truck
with water from a garden
hose coming from one of the
apartments, a workman was
cutting into a 6-inch main
line to  install a gate valve.
The end of the garden hose
was submerged in the tank
containing the pesticides,
and at the same time, the
water to the area was shut off
and the lines being drained
prior to the installation of the
gate valve. When the
workman cut the 6-inch
line, water started to drain
out of the cut, thereby setting
up a back-siphonage
condition. As a result, the
chemicals were siphoned out
of the truck, through the
garden hose, and into the
system, contaminating the
seventy five apartments.
  Repeated efforts to clean
and flush the lines were not
satisfactory and it was finally
decided to replace the water
line and all the  plumbing
that was affected. There were
no reports of illness, but
residents of the  housing
authority were told not to use
any tap water for any
purpose and they were given
water that was trucked into
the area by volunteer fire
department personnel. They
were without their normal
water supply for 27  days.
                       Recommended installation
                       of hose bibb vacuum breaker
                       backflow preventer

 Boiler Water
 Enters High School
 Drinking Water
                             Pesticide in
                             Drinking Water
                              Car Wash Water
                              in the Water  Mair
          Recommended installation
Street B   of backflow preventer^-^	Leaky check valve's
         Toxic rust inhibitor and
         defoamant containing
         sodium dichromate
A     high school in New
    Mexico, was closed for
 several days in June 1984
 when a home economics
 teacher noticed the water in
 the potable system was
 yellow. City chemists
 determined that samples
 taken contained levels of
 chromium as high as 700
 parts per million,
 "astronomically higher than
 the accepted levels of .05
 parts per million." The head
 chemist  said that it was
 miraculous that no one was
 seriously injured  or killed by
 the high levels  of chromium.
 The chemical was identified
 as sodium dichromate, a
 toxic form of chromium used
 in heating system boilers to
 inhibit corrosion of the metal
  No students or faculty were
 known to have  consumed
 any of the water; however,
 area physicians and hospitals
 advised that if anyone had
 consumed those high levels
 of chromium, the symptoms
 would be nausea, diarrhea,
and burning of the mouth
and throat. Fortunately, the
home economics teacher,
who first saw the discolored
water before school started,
immediately covered all
water fountains with towels
so that no one would drink
the water.
  Investigation disclosed that
chromium used in the
heating system boilers to
inhibit corrosion of metal
parts entered the potable
water supply system as a
result of backflow through
leaking check valves on the
boiler feed lines.
A    pesticide contaminated a
    North Carolina water
system in April, 1986,
prompting the town to warn
residents of 23 households
not to drink the water. The
residents in the affected area
were supplied drinking water
from a tank truck parked in
the parking lot of a
downtown office building
until the condition could be
cleared up. Residents
complained of foul smelling
water but there were no
reports of illness from
ingesting the water that had
been contaminated with a
pesticide containing
chlordane and heptachlor.
  Authorities stated that the
problem occurred  when a
water main broke  at the same
time that a pest control
service was filling a pesticide
truck with water. The
reduction in pressure caused
the pesticide from inside the
tank to be sucked  into the
building's water main. The
pesticide contaminated the
potable water supply of the
office building and
neighborhood area.
   This car wash
   cross-connection and
backpressure incident, which
occurred in February, 1979,
in the state of Washington,
resulted in backflow
chemical contamination of
approximately 100 square
blocks of water mains.
Prompt response by the watei
department prevented a
potentially hazardous water
quality degradation problem
without a recorded case of
  Numerous complaints of
grey-green and "slippery"
water were received by the
water department coming
from the same general area of
town. A sample brought to
the water department by a
customer confirmed the
reported problem and
preliminary analysis
indicated contamination with
what appeared to be a
detergent solution. While
emergency crews initiated
flushing operations, further
investigation within the
contaminated area signaled
the problem was probably
                             Recommended installation
                             of hose bibb vacuum breaker
                             backflow preventer

caused by a car wash, or
laundry, based upon the
soapy nature of the
contaminant. The source was
quickly narrowed down to a
car wash and the proprietor
was extremely cooperative in
admitting to the problem and
explaining how it had
occurred. The circumstances
leading up to the incident
were as follows:
  • On Saturday, February
10, 1979, a high pressure
pump broke down at the car
wash. This pump recycled
reclaimed wash and rinse
water and pumped it to the
initial scrubbers of the car
wash. No potable plumbing
connection is normally made
to the car wash's scrubber
  • After the pump broke
down, the car wash owner
was able  to continue
operation by connecting a
2-inch hose section
temporarily between the
potable supply within the car
wash, and the scrubber cycle
     • On Monday, February
   12, 1979, the owner repaired
   the high pressure pump and
   resumed normal car wash
   operations. The 2-inch
   hose connection
   (cross-connection) was not
     • Because of the
   cross-connection, the newly
   repaired high pressure pump
   promptly pumped a large
   quantity of the reclaimed
   wash/rinse water out of the
   car wash and into a 12-inch
   water main in the street. This
   in turn was delivered to the
   many residences and
   commercial establishments
   connected to the water main.
     Within 24 hours  of the
   incident, the owner of the  car
   wash had installed a
   2-inch reduced  pressure
   principle backflow preventer
   on his water service and all
   car wash establishments in
   Seattle that used a  wash
   water reclaim system were
   notified of the state
   requirement for backflow
       Wax injectors
_  Soap injectors
       i Recommended
       ,' installation of
        backflow preventer
                                               Jo washrooms
                                      Cafeteria drinking fountains
                                      and sanitation water
                         Reduced pressure principle backflow preventers
                         should have been installed at dockside outlets
                         and other locations
     Water fountains at an East
     Coast Shipyard  were
posted "No Drinking" as
workers flushed the water
lines to eliminate raw river
water that had entered the
shipyard following
contamination from
incorrectly connected water
lines between ships at the
pier and the shipyard. Some
third shift employees drank
the water before the pollution
was discovered and later
complained of stomach
cramps and diarrhea.
  The cause of the problem
was a direct cross-connection
between the on-board salt
water fire protection  water
system and the fresh water
connected to one of the ships
at the dock. While the
shipyard had been aware of
the need for backflow
protection at the dockside tie
up area, the device had not
been delivered and installed
prior to the time of the
incident. As a result, the salt
water on-board fire
protection system, being at a
greater pressure than the
potable supply, forced the
salt water, through
backpressure, into the
shipyard potable supply.
  Fortunately, a small
demand for potable water at
the time of the incident
prevented widespread
pollution in the shipyard and
the surrounding areas.
                                                     Potable water supply

Chlordane in  the
Water Main
                              Chromium in
                              Drinking  Water
Tn October, 1979,
Aapproximately three gallons
of chlordane, a highly toxic
insecticide, was sucked back
(back-siphoned) into the
water system of a residential
area of a good sized eastern
city. Residents complained
that the water "looked milky,
felt greasy, foamed and
smelled," and as one woman
put it, "It was similar to a
combination of kerosene and
Black Flag pesticide."
  The problem developed
while water department
personnel were repairing a
water main. A professional
exterminator, meanwhile,
was treating a nearby home
with chlordane for termite
elimination. The workman
for the exterminator company
left one end of a garden hose
that was connected to an
outside hose bibb tap in a
barrel of diluted  pesticide.
During the water service
interruption, the chlordane
solution was back-siphoned
from the barrel through the
house and into the water
  Following numerous
complaints, the water
department undertook an
extensive program of flushing
of the water mains and hand
delivered letters telling
residents to flush their lines
for four hours before using
the water. Until the water
lines were clear of the
contaminant, water was
hand-hauled into homes, and
people went out of their
homes for showers, meals
and every other activity
involving potable water.
Fortunately, due to the
obvious bad taste, odor and
color of the contaminated
water, no one consumed a
sufficient quantity to
endanger health.
  In July, 1982, a well
  meaning maintenance
mechanic, in attempting to
correct a fogging lens in an
overcooled laser machine,
installed a tempering valve in
the laser cooling line, and
inadvertently set the stage for
a backpressure backflow
incident that resulted in
hexavalent chromium
contaminating the potable
water of a large electronic
manufacturing company in
Massachusetts employing
9,000 people. Quantities of
  added to
  chilled water]
50 parts per million
hexavalent chromium were
found in the drinking water
which is sufficient to cause
severe vomiting, diarrhea,
and intestinal sickness.
Maintenance crews working
during the plant shutdown
were able  to eliminate the
cross-connection and
thoroughly flush the potable
water system, thereby
preventing a serious health
hazard from occurring.
  The incident occurred as
  • Laser machine lenses
were kept cool by circulating
chilled water that came from
a large refrigeration chiller.
                                                       feed pum
                                                              Recommended installation of
                                                              backflow preventer,—x
Recommended installation of hose bibb
vacuum breaker backflow preventer

                               Employee Health
                               Problems due to
The water used in the chiller
was treated with hexavalent
chromium, a chemical
additive used as an
anti-corrosive agent  and an
algicide. As  a result, the
chilled water presented a
toxic, non-potable substance
unfit for human consumption
but very acceptable  for
industrial process water. No
health hazard was present as
long as the piping was
identified, kept separate from
potable drinking water lines,
and not cross-connected to
the potable water supply.
  • A maintenance  mechanic
correctly reasoned that by
adding a  tempering  valve to
the chilled water line, he
could heat up the water a bit
and eliminate fogging of the
laser lenses resulting from
the chilled water being too
cold. The problem with the
installation of the tempering
valve was that a direct
cross-connection had been
inadvertently made  between
the toxic chilled water and
the potable drinking water
  • Periodic maintenance to
the chiller system was
performed in the summer,
requiring that an alternate
chiller feed pump be
temporarily  installed. This
replacement pump had an
outlet pressure of 150 psi.,
and promptly established an
imbalance of pressure at the
tempering valve, thereby
over-pressurizing the 60 psi.
potable supply. Backpressure
backflow resulted and
pushed the toxic chilled
water from the water heater
and then into the plant
potable drinking water
supply. Yellowish green
water started pouring out  of
the drinking fountains, the
washroom, and all potable
A     cross-connection
    incident occurring in a
modern seven-story office
building located in a large
city in New Hampshire, in
March, 1980, resulted in
numerous cases of nausea,
diarrhea, loss of time and
employee complaints as to
the poor quality of the water.
  On Saturday, March 1,
1980, a large fire occurred
two blocks away from a
seven-story office building in
this large New Hampshire
city. On Sunday, March 2,
1980, the maintenance crew
of the office building arrived
to perform the weekly
cleaning, and after drinking
the water from the drinking
fountains, and sampling the
coffee from the coffee
machines, noticed that the
water smelled rubbery and
had a strong bitter taste.
Upon notifying the
Manchester Water Company,
water samples were taken
and preliminary analysis
disclosed that the
contaminants found were not
the typical contaminants
associated with fire  line
disturbances. Investigating
teams suspected that either
the nearby fire could have
siphoned contaminants from
adjacent buildings into the
water mains, or the
contaminants could have
been caused by a plumbing
deficiency occurring within
the seven story building
  Water ph levels of the
building water indicated that
an injection of chemicals had
probably taken place within
the seven-story building.
Tracing of the water lines
within the building
pinpointed a 10,000 gallon
hot-water storage tank that
was used for heat storage in
the solar heating system. It
did not have any backflow
protection on the make-up
supply line! As this storage
tank pressure increased
above the supply pressure, as
a result of thermal expansion,
the potential for backpressure
backflow was present.
Normally, this would not
occur because a boost pump
in the supply line would
keep the supply pressure to
the storage tank always
greater than the highest tank
pressure. The addition of rust
inhibiting chemicals to this
tank greatly increased the
degree of hazard of the
liquid. Unfortunately, at the
same time that the fire took
place, the pressure in the
water mains was reduced to a
dangerously low pressure
and the low pressure cut-off
switches simultaneously shut
off the storage tank booster
pumps. This combination
allowed the boiler water,
together with its chemical
contaminants, the
opportunity to enter the
potable water supply within
the building. When normal
pressure was reestablished in
the water mains, the booster
pumps kicked in, and the
contaminated water was
delivered throughout the
Roof mounted solar panels
     Water mam
                              Recommended installation
                              of backflow preventers

Dialysis Machine
                                                            Creosote  in the
                                                            Water Mains
   Ethylene glycol, an
   anti-freeze additive to air
conditioning cooling tower
water, inadvertently entered
the potable water supply
system in a medical center in
Illinois in September, 1982,
and two of six dialysis
patients succumbed as a
direct or indirect result of the
  The glycol was added to
the air conditioning water,
and the glycol/water mix was
stored in a holding tank that
was an integral part of the
medical center's air
conditioning cooling system.
Pressurized make-up water to
the holding tank was
              Air conditioning units
supplied by a medical center
potable supply line and fed
through a manually operated
control valve. With this valve
open, or partially open,
potable make-up water
flowed slowly into the
glycol/water mixture in the
holding tank until it filled to
the point where the pressure
in the closed tank equalled
the pressure in the potable
water supply feed line. As
long as the potable feed line
pressure was at least equal
to, or greater than, the
holding tank pressure,  no
backflow could occur. The
stage was set for disaster,
                                   holding tank
                                   I  ^Submerged mlet
                                   I  \cross-connection
                            of backflow preventer 'f^.*
  It was theorized that
someone in the medical
center flushed a toilet or
turned on a faucet, which in
turn dropped the  pressure in
the potable supply line to the
air conditioning holding
tank. Since the manually
operated fill valve was
partially open, this allowed
the glycol/water mixture to
enter the medical center
potable pipelines  and flow
into the dialysis equipment.
The dialysis filtration system
takes out trace chemicals
such as those used in the city
water treatment plant, but the
system could not  handle the
heavy load of chemicals that
it was suddenly subjected to.
  The effect upon the
dialysis patients was
dramatic: patients became
drowsy, confused and fell
unconsious, and were
promptly removed to
intensive care where blood
samples were taken. The
blood samples revealed a
build-up of acid and the
medical director stated that,
"Something has happened in
dialysis." Dialysis was
repeated on the patients a
second and third  time.
  Tests of the water supply
to the filtration system
quickly determined the
presence of "an undesirable
chemical in the water
purification system." The
partially open fill valve was
then found that it had
permitted the glycol/water
mix to drain from the air
conditioning holding tank
into the medical center's
potable supply lines and  then
into the dialysis filtration
system equipment.
                                                    BacKpressure backflow
                                                                    -Mam water supply
                                                  Recommended installation
                                                  of backflow preventer
   Creosote entered the water
   distribution system of a
southeastern county water
authority in Georgia, in
November, 1984, as a result
of cross-connection between
a % inch hose that was being
used as a priming line
between a fire service
connection and the suction
side of a creosote pump. The
hose continually supplied
water to the pump to ensure
the pump was primed at all
times. However, while
repairs were being made to a
private fire hydrant, the
creosote back-siphoned into
the water mains and
contaminated a section of  the
water distribution system.
  Detailed investigation of
the cause of the incident
disclosed that the wood
preservative company, as parl
of their operation, pumped
creosote from collective pits
to other parts of their
operation. The creosote
pump would automatically
shut off when the creosote in
the pit was lowered to a
pre-determined level. After
the creosote returned to a
higher level, the pump would
re-start. This pump would
lose its  prime  quite often
prior to the pit refilling, and

                                                            Kool-Aid Laced
                                                            with Chlordane
 Street mam
                     Pnvate shut-off,--   Recommended installation
                    Recommended installation
                    of backflow preventers
to prevent the loss of prime,
the wood preservative
company would connect a
hose from a %-inch hose
bibb, located  on the fire
service line, tp the suction
side of the pump. The hose
bibb remained open at all
times in an effort to
continuously keep the pump
  Repairs were necessary to
one of the private fire
hydrants on the wood
preservative company
property, necessitating the
shutting down of one of two
service lines and removal of
the damaged fire hydrant for
repair. Since the hydrant was
at a significantly lower level
than the creosote pit, the
creosote back-siphoned
through a %-inch pump
priming hose connecting the
creosote pit to the fire service
  After the repairs were
made to the hydrant, and the
water service restored, the
creosote, now in the fire
lines, was forced into the
main water distribution
  In August, 1978, a
  professional exterminator
was treating a church located
in a small town in South
Carolina, for termite and pest
control. The highly toxic
insecticide chlordane was
being mixed with water in
small buckets, and garden
hoses were left submerged in
the buckets while the mixing
was being accomplished. At
the same time, water
department personnel came
by to disconnect the
parsonage's water line from
the church to install a
separate water meter for the
parsonage. In the process, the
water was shut off in the area
of the church building. Since
the church was located on a
steep hill, and as the
remaining water  in the  lines
was used by residents in the
area, the church  was among
the first places to experience
a negative pressure.  The
chlordane was quickly
siphoned into the water lines
within the church and
became mixed with the
Kool-Aid being prepared by
women for the vacation bible
school. Approximately  a
dozen children and three
adults experienced dizziness
and nausea.  Fortunately,
none required hospitalization
or medical attention.
                                        Recommended installation
                                        of hose bibb vacuum
                                        breaker backflow preventer

 Chapter  Three
Theory  of  Backflow
and  Backsiphonage
A                                 cross-connection 1 is the
                                link or channel
                            connecting a source of
                            pollution with a potable
                            water supply. The polluting
                            substance, in most cases a
                            liquid, tends to enter the
                            potable supply if the net
                            force acting upon the liquid
                            acts in the direction of the
                            potable supply. Two factors
                            are therefore essential for
                            backflow. First, there must  be
                            a Jink between the two
                            systems. Second, the
                            resultant force must be
                            toward the potable supply.
                              An understanding of the
                            principles of backflow and
                            back-siphonage requires an
                            understanding of the terms
                            frequently used in their
                            discussion. Force, unless
                            completely resisted, will
                            produce motion. Weight is  a
                            type of force resulting from
                            the earth's gravitational
                            attraction. Pressure fPJ is a
                            force-per-unit area, such as
                            pounds per square inch (psi).
                            Atmospheric pressure is the
                            pressure exerted by the
                            weight of the atmosphere
                            above the earth.
                              Pressure may be referred to
                            using an absolute scale,
                            pounds per square inch
                            absolute (psia), or gage scale,
                            pounds per square inch gage
                            (psig). Absolute pressure and
                            gage pressure are related.
                            Absolute pressure is equal  to
                            the gage pressure plus the
                            atmospheric pressure. At sea
                            level the atmospheric
                            pressure is 14.7 psia. Thus,
                              P absolute =  P gage + 14.7 psi
                              P gage =  P absolute -14.7 psi
  In essence then, absolute
pressure is the total pressure.
Gage pressure is simply the
pressure read on a gage. If
there is no pressure on the
gage other than atmospheric,
the gage would read zero.
Then the absolute pressure
would be equal to 14.7 psi
which is the atmospheric
  The term  vacuum indicates
that the absolute pressure is
less than the atmospheric
pressure and that the gage
pressure is negative. A
complete or total vacuum
would mean a pressure of 0
psia or -14.7 psig. Since it is
impossible to produce a total
vacuum, the term vacuum, as
used in the  text, will mean
all degrees of partial vacuum.
In a partial  vacuum, the
pressure would range from
slightly less than 14.7 psia
(0 psig) to slightly greater
than 0 psia  (-14.7 psig).
  Backsiphonage1 results in
fluid flow in an undesirable
or reverse direction. It is
caused by atmospheric
pressure exerted on a
pollutant liquid forcing it
toward a potable  water
supply system that is under a
vacuum. Back/low, although
literally meaning any type of
reversed flow, refers to the
flow produced by the
differential  pressure existing
between two systems both of
which are at pressures greater
than atmospheric.
Water Pressure

For an understanding of the
nature of pressure and its
relationship to water depth,
consider the pressure exerted
on the base of a cubic foot of
water at sea level. (See Fig. 1.)
The average weight of a cubic
foot of water is 62.4 pounds
per square foot gage. The
base may be subdivided into
144-square  inches with each
subdivision being subjected
to a pressure of 0.433 psig.
  Suppose  another cubic foot
of water were placed directly
on top of the first (See Fig. 2).
The pressure on the top
surface of the first cube
which was  originally
atmospheric, or 0 psig, would
now be 0.433  psig as a result
of the superimposed cubic
foot of water. The pressure of
the base of  the first cube
would also  be inreased by
the same amount of 0.866
psig, or two times the
original pressure.
Pressure exerted by 1 foot of
water at sea level.
                                    0 433 psig
                                                         1 See formal definition in the glossary of
                                                         the appendix.

  If this process were
 epeated with a third cubic
foot of water, the pressures at
the base of each cube would
be 1,299 psig, 0.866 psig, and
0.433 psig, respectively. It is
evident that pressure varies
with depth below a free
water surface1, in general
each foot of elevation change,
within a liquid, changes the
pressure by an amount equal
to the weight-per-unit area of
1 foot of the liquid. The rate
of increase for water is 0.433
psi per foot of depth.
  Frequently water pressure
is referred to using the terms
"pressure head" or just
"head," and is expressed in
units of feet of water. One
foot of head would be
equivalent to the pressure
produced at the base of a
column of water 1 foot in
depth. One foot of head or 1
foot of water is equal to 0.433
psig. One hundred feet of
head are equal to 43.3 psig.
 Pressure exerted by 2 feet of
 water at sea level.
          0 433 psig
 1See formal definition in the
 glossary of the appendix.
Siphon Theory

  Figure 3 depicts the
atmospheric pressure on a
water surface at sea level. An
open tube is inserted
vertically into the water;
atmospheric pressure, which
is 14.7 psia, acts equally on
the surface  of the water
within the tube and on the
outside of the tube.
Pressure on the free surface of a
liquid at sea level.
                                 147 psia
  If, as shown in Figure 4, the
tube is slightly capped and a
vacuum pump is used to
evacuate all the air from the
sealed tube, a vacuum with a
pressure of 0 psia is created
within the tube. Because the
pressure at any point in a
static fluid is dependent
upon the height of that point
above a reference line, such
as sea level, it follows that
the pressure within the tube
at sea level must still be 14.7
psia.  This is equivalent to the
pressure at the base of a
column of water 33.9 feet
high and with the column
open at the base, water
would rise to fill the column
to a depth of 33.9 feet. In
other words, the weight of
the atmosphere  at sea level
exactly balances the weight
of a column of water 33.9
feet in height. The absolute
pressure within the column
of water in Figure 4  at a
height of 11.5 feet is equal to
9.7 psia. This is a partial
vacuum with an equivalent
gage pressure of -5.0 psig.
  As a practical example,
assume the water pressure at
a closed faucet on the top of
a 100-foot high building to be
20 psig; the pressure on the
ground floor would then be
63.3 psig. If the pressure at
the ground were to drop
suddenly due to a heavy fire
demand in the area to 33.3
psig, the pressure at  the top
would be reduced to -10 psig.
If the building water system
were airtight, the water
would remain at the level of
the faucet because of the
partial vacuum created  by the
drop in pressure. If the  faucet
were opened, however,  the
                                                              Figure 4.
                                                              Effect of evacuating air from a
                                                                           'Zero" Absolute Pressure
vacuum would be broken and
the water level would drop to
a height of 77 feet above the
ground. Thus, the
atmosphere was supporting a
column of water 23 feet high.
  Figure 5 is a diagram of an
inverted U-tube that has been
filled with water and placed
in two open containers at sea
  If the open containers are
placed so  that the  liquid
levels in each container are
at the same height, a static
state will  exist; and the
pressure at any specified
level in either leg of the
U-tube will be the same.
                                                             FIGURE 5.
                                                             Pressure relationships in a
                                                             continuous fluid system at the
                                                             same elevation.
                                                                                    4 7 psia
                                                                                              The equilibrium condition
                                                                                            is altered by raising one of
                                                                                            the containers so that the
                                                                                            liquid level in one container
                                                                                            is 5 feet above the level of

the other. (See Fig. 6.) Since
both containers are open to
the atmosphere, the pressure
on the liquid surfaces in each
container will remain at 14.7
  If it is  assumed that a static
state exists, momentarily,
within the system shown in
Figure 6, the pressure in the
left tube  at any height above
the free surface in the left
container can be calculated.
The pressure at the
corresponding level in the
right tube above the free
surface in the right container
may also be calculated.
  As shown in Figure 6, the
pressure  at all levels in  the
left tube  would be less than
at corresponding levels  in the
right tube. In this case, a
static condition cannot exist
because fluid will flow from
the higher pressure to the
lower pressure; the flow
would be from the right tank
to the left tank. This
arrangement will  be
recognized as a siphon.  The
crest of a siphon cannot be
higher than 33.9 feet above
the upper liquid level, since
atmosphere cannot support a
column of water greater in
height than 33.9 feet.
Pressure relationships in a
continuous fluid system at
different elevations.
   8 2 psia
103 psia
          FIGURE 7.
          Backsiphonage in a plumbing
               Valve open
               Valve open

                   Closed supply
  Figure 7 illustrates how
this siphon principle can be
hazardous in a plumbing
system. If the supply valve is
closed, the pressure in the
line supplying  the faucet is
less than the pressure in the
supply line to the bathtub.
Flow will occur, therefore,
through siphonage, from the
bathtub to the open faucet.
  The  siphon actions cited
have been produced by
reduced pressures resulting
from a difference in the water
levels at two separated points
within continuous fluid
  Reduced pressure may also
be created within a fluid
system as a result of fluid
motion. One of the basic
principles of fluid mechanics
is the principle of
conservation of energy. Based
upon this principle, it may
be shown that as  a fluid
                               accelerates, as shown in
                               Figure 8, the pressure is
                               reduced. As water flows
                               through a constriction such
                               as a converging section of
                               pipe, the velocity of the
                               water increases; as a result,
                               the pressure is reduced.
                               Under such conditions,
                               negative pressures may be
                               developed in a pipe. The
                               simple aspirator is based
                               upon this principle. If this
                               point of reduced pressure is
                               linked to a  source of
                               pollution, backsiphonage of
                               the pollutant can  occur.
                                        FIGURE 8.
                                        Negative pressure created by
                                        constricted flow.
                                                   -10 psig
                                        + 30 psig               +30 psig
                                        FIGURE 9.
                                        Dynamically reduced pipe
                                                             From pollution source
                                                                                 To fixture
                                                                    Booster pump
  One of the common
occurences of dynamically
reduced pipe pressures is
found on the suction side of
a pump. In many cases
similar to the one illustrated
in Figure 9, the line
supplying the booster pump
is undersized or does not
have sufficient pressure to
deliver water at the rate at
which the pump  normally
operates. The rate of flow in
the pipe may be increased b\
a further reduction  in
pressure at the pump intake.
This often results in the
creation of negative pressure
at the pump intake. This
often results in the  creation
of negative pressure. This
negative pressure may
become low enough in some
cases to cause vaporization o
the water in the line.
Actually, in the illustration
shown, flow from the source
of pollution would  occur
when pressure on the suctioi
side"of the pump is less than
pressure of the pollution
source; but this is back/low,
which will be discussed
  The preceding  discussion
has described some of the
means by which negative
pressures may be created anc
which frequently occur to
produce backsiphonage. In
addition to the negative
pressure or reversed force
necessary to cause
backsiphonage and  backflow,
there must also be the
cross-connection  or
connecting link between the
potable water supply and the
source of pollution. Two
basic types of connections
may be created in piping
systems. These are the solid
pipe with valved connection
and the submerged  inlet.

Valved connection between
potable water and nonpotable
Non potable
Figures 10 and 11 illustrate
solid connections. This type
of connection  is often
installed where it is
necessary to supply an
auxiliary piping system from
the potable source. It is a
direct connection of one pipe
to another pipe or receptacle.
  Solid pipe connections are
often made to  continuous or
intermittent waste lines
where  it is assumed that the
flow will be in one direction
only. An example of this
would be used cooling water
from a water jacket or
condenser as shown in Figure
11.  This type of connection is
usually detectable but
creating a concern on the
Valved connection between
potable water and sanitary
part of the installer about the
possibility of reversed flow is
often more difficult. Upon
questioning, however, many
installers will agree that the
solid connection was made
because the sewer is
occasionally subjected to
  Submerged inlets are found
on many common plumbing
fixtures and are sometimes
necessary features of the
fixtures if they are to
function properly. Examples
of this type of design are
siphon-jet urinals or water
closets, flushing rim slop
sinks, and dental  cuspidors.
Oldstyle bathtubs and
lavatories had supply inlets
below the flood level rims,
but modern sanitary design
has minimized or eliminated
this hazard in new fixtures.
Chemical and industrial
process vats sometimes have
submerged inlets  where the
water pressure is  used as an
aid in diffusion, dispersion
and agitation of the vat
contents. Even though the
supply pipe may  come from
the floor above the vat,
backsiphonage can occur as it
has been shown that the
siphon action can raise a
liquid such as water almost
34 feet. Some submerged
inlets difficult to  control are
those which are not apparent
until a significant change in
water level occurs  or where a
supply may be conveniently
extended below the liquid
surface by means of a hose or
auxiliary piping. A
submerged inlet may be
created in numerous ways,
and its detection in some of
these subtle forms  may be
  The illustrations included
in part B of the appendix are
intended to describe typical
examples of backsiphonage,
showing in each case the
nature of the  link or
cross-connection, and the
cause of the negative

                                     Backflow1, as described in
                                     this manual, refers to
                                     reversed flow due to
                                     backpressure other than
                                     siphonic action. Any
                                     interconnected fluid systems
                                     in which the pressure of one
                                     exceeds the pressure of the
                                     other may have flow from
                                     one to the other as a result  of
                                     the pressure differential. The
                                     flow will occur from the zone
                                     of higher pressure to the zone
                                     of lower pressure. This type
                                     of backflow is  of concern in
                                     buildings where two or more
                                     piping systems are
                                     maintained. The potable
                                     water supply is usually
                                     under pressure directly from
                                     the city  water main.
                                     Occasionally, a booster pump
                                     is used.  The auxiliary system
                                     is often  pressurized by a
                                     centrifical pump, although
                                     backpressure may be caused
                                     by gas or steam pressure from
                                     a boiler.  A reversal in
                                     differential pressure may
occur when pressure in the
potable system drops, for
some reason, to a pressure
lower than that in the system
to which the potable water is
  The most positive method
of avoiding this type of
backflow is the total or
complete separation of the
two systems. Other  methods
used involve the installation
of mechanical devices. All
methods require routine
inspection and maintenance.
  Dual piping systems are
often installed for extra
protection in the event of an
emergency or possible
mechanical failure of one of
the systems. Fire protection
systems are an example.
Another example is the use
of dual water connections to
boilers. These installations
are sometimes
interconnected, thus creating
a health hazard.
  The illustrations in  part C
of the appendix depict
installations where backflow
under pressure can  occur,
describing the
cross-connection and the
cause of the reversed flow.
Sanitary sewer
                                                            1 See forma! definition in the glossary of
                                                            the appendix.

Chapter Four
                                                       Air Gap
Methods  and
for the  Prevention  of
Backflow and
A                                wide choice of devices
                               exists that can be used to
                            prevent back-siphonage and
                            backpressure from adding
                            contaminated fluids or gases
                            into a potable water supply
                            system. Generally, the
                            selection of the proper device
                            to use is based upon the
                            degree of hazard posed by
                            the cross-connection.
                            Additional considerations are
                            based upon piping size,
                            location,  and the potential
                            need to periodically test the
                            devices to insure proper
                             There are six basic types of
                            devices that can be used to
                            correct cross-connections: air
                            gaps, barometric loops,
                            vacuum breakers — both
                            atmospheric and  pressure
                            type, double check with
                            intermediate atmospheric
                            vent, double check valve
                            assemblies, and reduced
                            pressure principle devices. In
                            general, all manufacurers of
                            these devices, with the
                            exception of the barometric
                            loop, produce them to one  or
                            more of three basic
                            standards, thus insuring the
                            public that dependable
                            devices are being utilized
                            and marketed. The major
                            standards in the industry are:
                            American Society of Sanitary
                            Engineers (ASSE), American
                            Water Works Association
                            (AWWA), and the University
                            of California Foundation for
                            Cross-Connection Control
                            and Hydraulic Research.
 Air gaps are non-mechanical
 backflow preventers that are
 very effective devices to be
 used where either
 back-siphonage or
 backpressure conditions may
 exist. Their use is as old as
 piping and plumbing itself,
 but only relatively recently
 have standards been issued
 that standardize their design.
 In general, the air gap must
 be twice the supply pipe
 diameter but never  less than
 one inch.  See Figure 12.
 Air Gap
  An air gap, although an
extremely effective backflow
preventer when used to
prevent back-siphonage and
backpressure conditions,
does interrupt the piping
flow with corresponding loss
of pressure for subsequent
use. Consequently, air gaps
are primarily used at end of
the line service where
reservoirs or storage tanks are
desired. When contemplating
the use of an air gap, some
other considerations are:
(1)  In a continuous piping
system, each air gap requires
the added expense of
reservoirs and secondary
pumping systems.
(2)  The air gap may be
easily defeated in the event
that the "2D" requirement
was purposely or
inadvertently compromised.
Excessive splash may be
encountered in the event that
higher than anticipated
 pressures or flows occur. The
 splash may be a cosmetic or
 true potential hazard — the
 simple solution being to
 reduce the "2D" dimension
 by thrusting the supply pipe
 into the receiving funnel. By
 so doing, the air gap is
 (3)  At an air gap, we expost
 the water to the surrounding
 air with its inherent bacteria,
 dust particles, and other
 airborn pollutants or
 contaminants. In addition,
 the aspiration effect of the
 flowing water can drag down
 surrounding pollutants into
 the reservoir or holding tank,

 (4)  Free chlorine can come
 out of treated water as a
 result of the air gap and the
 resulting splash and churnin;
 effect as the water enters the
 holding tanks. This reduces
 the ability of the water to
 withstand bacteria
 contamination during long
 term storage.
 (5)  For the above reasons,
 air gaps must be inspected as
 frequently as mechanical
 backflow preventers.  They
 are not exempt from an
 in-depth cross-connection
 control program  requiring
 periodic inspection of all
 backflow devices.
   Air gaps may be fabricated
 from commercially available
 plumbing components or
 purchased as separate units
 and integrated into plumbing
 and piping systems. An
 example of the use of an air
 gap is shown in  Figure 13.
 Air Gap in a Piping System
Supply piping
                                                                                     tank or reservoir

Barometric Loop
Atmospheric Vacuum
The barometric loop consists
of a continuous section of
supply piping that abruptly
rises to a height of
approximately 35 feet and
then returns back down to
the originating level. It is a
loop in the piping system
that effectively protects
against back-siphonage. It
may not be used to protect
against back-pressure.
  Its operation, in the
protection against
back-siphonage, is based
upon the principle that a
water column, at sea level
pressure, will not rise above
33.9  feet  (Ref. Chapter 3,
Fig. 4 Page 13).
  In  general, barometric
loops are locally fabricated,
and are 35 feet high.
Barometric Loop
 These devices are among the
 simplest and least expensive
 mechanical types of backflow
 preventers and, when
 installed properly, can
 provide excellent protection
 against back siponage. They
 must not be utilized to
 protect against backpressure
 conditions. Construction
 consists usually of a
 polyethylene float which is
 free to travel on a shaft and
 seal in the uppermost
 position against atmosphere
 with an elastomeric disc.
 Water flow lifts the float,
 which then causes the disc to
 seal. Water pressure keeps
 the float in the upward
 sealed position. Termination
 of the water supply will
 cause the  disc to drop down
 venting the unit to
 atmosphere and thereby
 opening downstream piping
 to atmospheric pressure, thus
 preventing back-siphonage.
 Figure 15  shows a typical
 atmospheric breaker.
  In general, these devices
 are available in Vz inch
 through 3 inch size and must
 be installed vertically, must
 not have shut-offs
 downstream, and must be
 installed at least 6 inches
 higher than the final outlet.
 They cannot be tested once
 they are installed in the
 plumbing  system, but are, for
 the most part,  dependable,
trouble-free devices for
back-siphonage protection.

 Atmospheric Vacuum Breaker
Atmospheric Vacuum Breaker
Typical Installation
Figure 16 shows the
generally accepted
installation requirements -
note that no shut-off valve is
downstream of the device
that would otherwise keep
the atmospheric  vacuum
breaker under constant
  Figure  17 shows a typical
installation of an atmospheric
vacuum breaker  in a
plumbing supply system.
                                                            FIGURE 17
                                                            Atmospheric Vacuum Breaker
                                                            in Plumbing Supply System
                                  Flow condition

Hose Bibb
Vacuum Breakers
                              Vacuum Breakers
These small devices are a
specialized application of the
atmospheric vacuum breaker.
They are generally attached
to sill cocks and in turn are
connected to hose  supplied
outlets such as garden hoses,
slop sink hoses,  spray
outlets, etc. They consist of a
spring loaded  check valve
that seals against an
atmospheric outlet when
water supply pressure is
turned on. Typical
construction is shown in
Figure 18.
   When the water supply is
turned off, the device vents
to atmosphere, thus
protecting against
back-siphonage conditions.
They should not be used as
backpressure devices. Manual
drain options  are available,
together with  tamper-proof
versions. A typical
installation is shown in
Figure 19.
Hose Bibb Vacuum Breaker
Typical Installation of Hose
Bibb Vacuum Breaker
This device is an outgrowth
of the atmospheric vacuum
breaker and evolved in
response to a need to have an
atmospheric vacuum breaker
that could be utilized under
constant pressure and that
could be tested in line. A
spring on top of the disc and
float assembly, two added
gate valves, test cocks, and
an additional first check,
provided the answer to
achieve this device. See
Figure 20.
  These units are available in
the general configurations as
shown in Figure 20 in sizes
Vz through 10 inch and have
broad usage in the agriculture
and irrigation market.
Typical agricultural and
industrial applications are
shown in Figure 21.
                               FIGURE 20
                               Pressure Vacuum Breaker
                                                                      Test cock
  Again, these devices may
be used under constant
pressure but do not protect
against backpressure
conditions. As a result,
installation must be at least 6
to 12 inches higher than the
existing outlet.
                                                                                             0 ~\	-Spring
                                                                                                          Gate valve
                                                                                  2'/2 inches thru 10 inches

  Double Check with
  Atmospheric Vent

  The need to provide a
  compact device in Yz inch
  and 3/4 inch pipe sizes that
  protects against moderate
  hazards, is capable of being
  used under constant pressure
  and that protects against
  backpressure, resulted in this
  unique backflow preventer.
  Construction is basically a
  double check valve having an
  atmospheric vent located
  between the two checks (See
  Figure 22).
    Line pressure keeps the
  vent closed, but zero supply
  pressure or back-siphonage
  will open the inner chamber
  to atmosphere. With this
  device, extra protection is
  obtained through the
  atmospheric vent capability.
  Figure 23 shows a typical use
  of the device on a residential
  boiler supply line.
Double Check Valve with
Atmospheric Vent
            1st check
                            2nd check
Typical Residential Use of
Double Check with
Atmospheric Vent
                              Automatic feed valve
ypical Agricultural and
industrial Application of
ressure Vacuum Breaker
                                                            Double Check Valve
A double check valve is
essentially two single check
valves coupled within one
body and furnished with test
cocks and two tightly closing
gates valves (See Figure 24).
  The test capability feature
gives this device a big
advantage over the use of two
independent check valves in
that  it can be readily tested
to determine if either or both
check valves are inoperative
or fouled by debris. Each
check is spring loaded closed
and requires approximately a
pound of pressure to open.
  This spring loading
provides the ability to "bite"
through small debris and still
seal — a protection feature
not prevalent in unloaded
swing check valves. Figure
24 shows a cross section of
double check valve complete
with test cocks. Double
checks are commonly used to
protect against low to
medium hazard installations
such as food processing
steam kettles and apartment
projects. They may be used
under continuous pressure
and protect against both
back-siphonage and
backpressure conditions.
                                                                                           FIGURE 24
                                                                                           Double Check Valve

 Double Check Detector
                              Residential Dual Check
 This device is an outgrowth
 of the double check valve
 and is primarily utilized in
 fire line installations. Its
 purpose is to protect the
 potable supply line from
 possible contamination or
 pollution from fire line
 chemical additives, booster
 pump fire line backpressure,
 stagnant "black water" that
 sits in fire lines over
 extended periods of time, the
 addition of "raw" water
 through outside fire pumper
 connections (Siamese
 outlets), and the detection of
 any water movement in the
 fire line water due to fire line
 leakage or deliberate water
 theft. It consists of two,
 spring loaded  check valves, a
 by-pass assembly with water
 meter and double check
 valve, and two tightly closing
 gate valves.  See Figure 25.
 The addition of test cocks
 makes the device testable to
 insure proper  operation of
 both the primary checks  and
 Double Check Detector Check
the by-pass check valve. In
the event of very low fire line
water usage, (theft of water)
the low pressure drop
inherent in the by-pass
system permits the low flow
of water to be metered
through the by-pass system.
In a high flow demand,
associated with deluge fire
capability, the main check
valves open, permitting high
volume, low restricted flow,
through the two large spring
loaded check valves.
The need to furnish reliable
and inexpensive
back-siphonage and
backpressure protection for
individual residences
resulted in the debut of the
residential  dual check.
Protection of the main
potable supply from
household hazards such as
home photograph chemicals,
toxic insect and garden
sprays, termite control
pesticides used by
exterminators, etc., reinforced
                              FIGURE 26
                              Residential Dual Check
a true need for such a devic
Figure 26 shows a cutaway
the device.
  It is sized for 1/2, 3/4, anc
1-inch service lines and is
installed immediately
downstream of the water
meter. The use of plastic
check modules and
elimination of test cocks an
gate valves keeps the cost
reasonable while providing
good, dependable protectioi
Typical installations are
shown in Figures 27 and 28
                                                             FIGURE 27
                                                             Residential Installation
                                                                       water meter
                                                                FIGURE 28
                                                                Copper Horn
                                                                                       Residential dual check
                                                                    1Vi" meter thread female inlet with
                                                                    1" NPT Thread female union outlet
                                                                                           Water meter

Reduced Pressure
Principle Backflow

Maximum protection is
achieved against
back-siphonage and
backpressure conditions
utilizing reduced pressure
principle backflow
preventers. These devices are
essentially modified double
check valves with an
atmospheric vent capability
placed between the two
checks and designed such
that this "zone" between the
two checks is always kept at
least two pounds less than
the supply pressure. With
this design criteria, the
reduced pressure principle
backflow preventer can
provide protection against
back-siphonage and
backpressure when both the
first and second checks
become fouled. They can be
used under constant pressure
and at high hazard
installations. They are
furnished with test cocks and
gate valves to enable testing
and are available in sizes %
inch through 10 inch.
  Figure 29A shows typical
devices representative  of %
inch through 2 inch size and
Figure 29B shows typical
devices representative  of 2V->
inch through 10 inch sizes.
Reduced Pressure Zone
Backflow Preventer
Reduced Pressure Zone
Backflow Preventer
2a/2 inch thru 10 inches
                                                          Reduced pressure zone
                                                  1st check valve            2nd check valve
                                                                     Relief valve (rotated 90° for clarity)

   The principles of operation
 of a reduced pressure
 principle backflow preventer
 are as follows:
   Flow from the left enters
 the central chamber against
 the pressure exerted by the
 loaded check valve \. The
 supply pressure is reduced
 thereupon by a
 predetermined amount. The
 pressure in the central
 chamber is maintained lower
 than the incoming supply
 pressure through the
 operation of the relief valve
 3, which discharges to the
 atmosphere whenever the
 central chamber pressure
 approaches within a few
 pounds of the inlet pressure.
 Check valve 2 is lightly
 loaded to open with a
 pressure drop of 1 psi in the
 direction of flow and is
 independent of the pressure
 required to open the relief
valve. In the event that the
pressure increases
downstream from the device,
tending to reverse the
direction of flow, check valve
2 closes, preventing
backflow. Because all valves
may leak as a result of wear
or obstruction, the protection
provided by the check valves
is not considered sufficient.
If some obstruction prevents
check valve 2 from closing
tightly,  the leakage back into
the central chamber would
increase the pressure in this
zone, the relief valve would
open, and flow would be
discharged to the
  When the supply pressure
drops to the minimum
differential required to
operate the relief valve, the
pressure in the central
chamber should be
atmospheric. If the inlet
pressure should become less
than atmospheric pressure,
relief valve 3 should remain
fully open to the atmosphere
to discharge any water which
may be caused to backflow as
a result of backpressure and
leakage of check valve 2.
  Malfunctioning of one or
both of the check valves or
relief valve should always be
indicated by a discharge of
water from the relief port.
Under no circumstances
should plugging of the relief
port be permitted because the
device depends upon an
open port for safe operation.
The pressure loss through the
device may be expected to
average between 10 and 20
psi within the normal range
of operation, depending upon
the size and flow rate of the
  Reduced pressure principle
backflow preventers are
commonly installed on high
hazard installations such as
plating plants, where they
would protect against
primarily back-siphonage
potential, car washes where
they would protect against
backpressure conditions, and
funeral parlors, hospital
autopsy rooms, etc. The
reduced pressure principle
backflow preventer forms the
backbone of cross-connection
control programs. Since it is
utilized to protect against
high hazard installations, and
since high hazard
installations are the first
considerations in protecting
public health and safety,
these devices are installed in
large quantities over a broad
range of plumbing and water
works installations. Figures
31 and 32 show typical
installations of these devices
on high hazard installations.
 Reduced Pressure Zone
 Backflow Preventer — Principle
 of Operation
 direction of flow
                                 Reversed direction of flow
                               FIGURE 31
                               Plating Plant Installation
                                                              Reduced pressure principle backflow preventer^—-^ ^Z$&
                         Reduced pressure principle backflow preventer
                                                              FIGURE 32
                                                              Car Wash Installation

Typical By-pass Configuration
Reduced Pressure Principle
                                                                              FIGURE 34
                                                                              Typical Installation
                                                                              Reduced  Pressure Principle Device
                                                                              Horizontal Illustration
               Reduced pressure
               principle device
                                                                                                              Reduced pressure principle device
                                                                                                                              12' mm 30  max
                                                                                  Note  Device to be set 12" minimum from wall
                     Reduced pressure principle device
                                       Air gap
                                                                              FIGURE 35
                                                                              Typical Installation
                                                                              Reduced Pressure Principle Device
                                                                              Vertical Installation
Note Devices to be set a mm of 12" and a max of 30" from the floor and
12" from any wall
                                                                                                       Reduced pressure principle device
                                                                              Note  (1) Refer to manufacturers installation data for vertical mount
                                                                              (2) Unit to be set at a height to permit ready access for testing and service
                                                                              (3) Vertical installation only to be used if horizontal  installation cannot be

    FIGURE 36
    Typical Installation
    Double Check Valve
    Horizontal and Vertical
Typical Installation
Residential Dual Check with
Straight Set and Copperhorn
                            Double check valve
                               (unit to be set at a height
                               that permits ready access
                               for testing and service)
                           Copperhorn with water meter
                                                                                                          3/4" ball valve
                             Residential dual check
                          Water meter in copperhorn

                          3/4" ball valve
                                                                                                           3/4" K-copper
    Note: Vertical installation only to be used if
    horizontal installation cannot be  achieved

 Chapter  Five
Testing  Procedures
for  Backflow
                               Prior to initiating a test of
                               any backflow device, it is
                             recommended that the
                             following procedures be
                             1. Permission be obtained
                             from the owner, or his
                             representative, to shut down
                             the water supply. This is
                             necessary to insure that since
                             all testing is accomplished
                             under no-flow conditions, the
                             owner is aware that his water
                             supply will be temporarily
                             shut off while the testing is
                             being performed. Some
                             commercial and industrial
                             operations require constant
                             and uninterrupted water
                             supplies for cooling, boiler
                             feed, seal pump water, etc.
                             and water service
                             interruption cannot be
                             tolerated. The water  supply
                             to hospitals and continuous
                             process  industries cannot be
                             shut off without planned and
                             coordinated shut downs. The
                             request to shut down the
                             water supply is therefore a
                             necessary prerequisite to
                             protect the customer as well
                             as limit  the liability of the
                              Concurrent with the
                             request for permission to
                             shut off the water, it is
                             advisable to point out to the
                             owner, or his representative,
                             that while the water  is shut
off during the test period,
any inadvertent use of water
within the building will
reduce the water pressure to
zero. Backsiphonage could
result if unprotected
cross-connections existed
which would contaminate
the building water supply
system. In order to address
this situation, it is
recommended that the owner
caution the inhabitants of the
building not to use the water
until the backflow test is
completed and the water
pressure restored. Additional
options available to the
building owner would be the
installation of two backflow
devices in parallel that
would enable a protected
by-pass flow around the
device to be tested. Also, if
all water outlets are protected
within the building with
"fixture outlet protection"
backflow devices,
cross-connections would not
create a problem in the event
of potential back-siphonage
conditios occurring while
devices are tested, or for any
other reason.
2. Determine the type of
device to be tested i.e., double
check valve or reduced
pressure principle device.
3. Determine the flow
direction. (Reference
directional flow arrows or
wording provided by the
manufacturer on the device.)
4. Number the test cocks,
bleed  them of potential
debris, and assemble
appropriate test cock
adapters and bushings that
may be required.
5. Shut off the downstream
(number 2) shut-off valve.
(Ref. item (1) above.)
6.  Wait several moments prior
to hooking up the test kit
hoses when testing a reduced
pressure principle device. If
water exits the relief valve, in
all likelihood, the first check
valve is fouled and it is
impractical to proceed with
the testing until the valve is
serviced. This waiting period
is not necessary when testing
double check valves.
7. Hook up the test kit hoses
in the manner appropriate to
the device being tested and
the specific test being
  Test personnel are
cautioned to be aware and
follow local municipal,
county, and state testing
requirements and guidelines
as may be dictated by local
authority. The following test
procedures are guidelines for
standard, generally
acceptable test procedures
but may be amended,
superceded, or modified by
local jurisdiction.

Test  Equipment
For field testing of reduced
pressure principle backflow
preventers and double check
valve assemblies, a
differential pressure test
gauge is utilized having a 0
to 15 psi range and a working
pressure of 500 psi.
Appropriate length of hoses
with necessary fittings
accompany the test gauge.
Several manufactured test
kits are commercially
available that incorporate the
differential gauge, hoses, and
fittings and are packaged for
ease of portability and come
with protective enclosures or
straps for hanging. Calibrated
water columns are
commercially available that
are portable and come with
carrying cases.
  It is important that all test
equipment be periodically
checked for calibration.

Pressure Vacuum Breaker
(Figure 38)
Field testing of a  pressure
vacuum breaker involves
testing both the internal
spring loaded soft seated
check valve as well as testing
the spring loaded air inlet
valve. The testing must be
performed with the device
pressurized and the air inlet
closed. The number 2
shut-off valve must also be
closed and the air inlet valve
canopy removed.

Method 1
Using a differential pressure

Test 1 Test the internal check
valve for tightness of 1 psid
in the direction of flow.
1.  With the valve body
    under pressure, (number 2
    shut-off valve closed and
    number  1 shut-off valve
    open) bleed test cocks
    number  1 and number 2.
2.  Hook up the high
    pressure hose to number 1
    test cock and the low
    pressure hose to number
    2 test cock.
          Air inlet valve canopy
          Loaded air inlet valve

     Test .cock No 2
              No 2 shut off valve
         Check valve

         Test cock No 1
          No 1 shut off valve
         FIGURE 38
    Bleed the high pressure
    hose, and low pressure
    hose, in that order, and
    close the test kit needle
    valves slowly.
    Record the differential
    pressure on the gauge. A
    reading of 1  psid is
    acceptable to insure a
    tight check valve.

Test 2 Test the air inlet valve
for a breakaway  of 1 psi.
1.   Connect the  high
    pressure hose to test cock
    number 2, and bleed the
    high pressure hose.
2.   Shut off number 1
    shut-off valve.
3.   Slowly open the bleed
    valve of the test kit, and
    observe and  record the
    psi when the air inlet
    poppet opens. This
    should be a minimum of
    1 psi. Restore the valve to
    normal service.
Method 2
Using a water column sight
tube and 90 degree elbow
fitting with bleed needle

Test 1 Test the internal check
valve for tightness of 1 psid
in the direction of flow.
1.  Assemble sight tube to
    test cock number 1.  Open
    test cock and fill the tube
    to a minimum of 36
    inches of water height.
2.  Close number 1 shut-off
3.  Open test cock number 2.
    The air inlet valve should
    open and discharge water
    through number 2 test
4.  Open number 1 test cock.
    The sight tube level of
    water should drop slowly
    until it stabilizes. This
    point should be a
    minimum of 28 inches of
    water column which
    equals 1 psi.

Test 2 Test the air inlet valve
for a breakaway  of 1  psi.
1.  Assemble sight tube to
    test cock number 2. Open
    test cock number 2 and
    fill the tube to a
    minimum of 36 inches of
    water height.
2.  Close number 1 shut-off
3.  Bleed water  slowly from
    the  number 2 test cock
    bleed needle and observe
    the  water column height
    as it drops.
4.  At the point when the air
    inlet valve pops open,
    record the height of the
    water column. This point
    should be a minimum of
    28 inches of water
    column which equals 1
Restore the valve to normal
Reduced Pressure
Principle Backflow
(Figure 39)

Field testing of a reduced
pressure  principle backflow
preventer is accomplished
utilizing  a differential
pressure  gauge. The device is
tested for three optional
characteristics: i.e., (1) the fir;
check valve is tight and
maintains a minimum  of 5
psi differential pressure,  (2)
the second check valve is
tight against backpressure
and (3) the relief valve opens
at a minimum of 2 psi below
inlet supply pressure. Testing
is performed as follows:
Step 1 Test  to insure that the
first check valve is tight and
maintains a  minimum
pressure  of 5 psi differential
1.  Verify that number 1
    shut-off  valve is open.
    Close number 2 shut-off
    valve. If there is no
    drainage from the relief
    valve it  is  assumed that
    the first  check is tight.
2.  Close all test kit valves.
3.  Connect the high
    pressure hose to test  cock
    number  2.
4.  Connect the low pressure
    hose  to test cock number
5.  Open test cocks number
    2  and number 3.
6.  Open high side bleed
    needle valve on test kit
    bleeding the air from the
    high  hose. Close the high
    side bleed needle valve.
7.  Open the low side  bleed
    needle valve on test kit
    bleeding air from the low
    hose. Close the low side
    bleed needle valve.
    Record the differential
    gauge pressure. It should
    be a minimum of 5 psid.

 Step 2 Test to insure that the
 second check is tight against
 backpressure.  (Figure 40)
 1.  Leaving the hoses hooked
     up as in the conclusion
     of Step 1 above, connect
     the bypass  hose to test
     cock number 4.
 2.  Open test cock number 4,
     the high control needle
     valve and the bypass
     hose control needle valve
     on the test  kit. (This       3'
     supplies high pressure
     water downstream of
                                         ypass hose
check valve number 2.) If
the differential pressue
gauge falls off and water
comes out of the relief
valve, the second check
is recorded as leaking. If
the differential pressure
gauge remains steady,
and no water comes out
of the relief valve, the
second check valve is
considered tight.
To check the tightness of
number 2 shut-off valve,
leave the hoses hooked
up the same as at the
conclusion of Step 2
above, and then close test
cock number 2. This
stops the supply of any
high pressure water
downstream of check
valve number 2. If the
differential pressure
gauge reading holds
steady, the number 2
shut-off valve is recorded
as being tight.  If the
differential pressure
gauge drops to zero, the
number 2 shut-off valve
is recorded as  leaking.
  With a leaking number
2 shut-off valve, the
device is, in most cases,
in a flow condition and
the previous readings
taken are invalid. Unless
a non-flow condition can
be achieved, either
through the operation of
an additional shut-off
downstream, or the use
of a compensating
temporary by-pass hose,
(Ref: Fig. 40), accurate  test
results will not be
Step 3 To check that the
relief valve opens at a
minimum pressure  of 2 psi
below inlet pressure.
1.  With the hoses  hooked
    up the same as  at the
    conclusion of Step #2 (3)
    above, slowly open up
    the low control needle
    valve on  the test kit and
    record the differential
    pressure  gauge reading at
    the point when the water
    initially starts to drip
    from the  relief valve
    opening.  This pressure
    reading should  not be
    below 2 psid.
  This completes the
standard field test for a
reduced pressure principle
backflow preventer. Before
removal of the test
equipment, the tester should
insure that he opens number
2 shut-off valve thereby
reestablishing flow. Also, the
test kit should be thoroughly
drained of all water to
prevent freezing by  opening
all control needle valves and
bleed needle  valves.
  All test data should be
recorded on appropriate
forms. (Ref: sample  Page 45)
Temporary b'
                                                                                           Note: The steps outlined above
                                                                                           may vary in sequence depending
                                                                                           upon local regulations and/or

Double Check Valve
(Figure 41)

Some field test procedures
for testing double check
valve assemblies require that
the number 1 shut-off valve
be closed to accomplish the
test.  This procedure may
introduce  debris such as rust
and tuberculin into the valve
that will impact against
check valve number 1 or
number 2  and compromise
the sealing quality. This
potential problem should be
considered prior to the
selection of the appropriate
test method.
  Two test methods, one
requiring closing of the
number 1  shut-off valve, and
one without this requirement
are presented below:

Method 1
Utilizing the differential
pressure gauge and not
shutting off number 1
shut-off valve. (Figure 41)
Step 1 checking check valve
number 1
1.  Verify that the number 1
    shut-off is open. Shut off
    number 2  shut-off valve.
2.  Connect the high hose to
    test cock number 2.
3.  Connect the low hose to
    test cock number 3.
4.  Open  test  cocks 2 and 3.
5.  Open  high side bleed
    needle valve on test kit
    bleeding the air from the
    high hose. Close the high
    side bleed needle valve.
6.  Open low side bleed
    needle valve on test kit
    bleeding the air from the
    low hose.  Close the low
    side bleed needle valve.
7.  Record the differential
    gauge pressure reading. It
    should be a minimum of
    1 psid.
8.  Disconnect the hoses.
           Control needle valves
Step 2 Checking check valve
number 2.
1.   Connect the high hose to
    test  cock number 3.
2.   Connect the low hose to
    test  cock number 4.
3.   Open test cocks number
    3 and 4.
4.   Open high side bleed
    needle valve on test kit
    bleeding the air from the
    high hose. Close the high
    side bleed needle valve.
5.   Open low side bleed
    needle valve on test kit
    bleeding the air from the
    low hose. Close the low
    side bleed needle valve.
6.   Record the differential
    gauge pressure reading. It
    should be a minimum of
    1 psid.
7.   Disconnect the hoses.
  To check tightness of
number 2 shut-off valve, both
the check valves must be
tight and holding a minimum
of 1 psid. Also, little or no
fluctuation of inlet supply
pressure can be tolerated.
                                          Bypass hose
                                            FIGURE 41
  The testing is performed as
1.   Connect the high hose to
    number 2 test cock.
2.   Connect the low hose to
    number 3 test cock.
3.   Connect the by-pass hose
    to number 4 test cock.
4.   Open test cocks numbers
    2, 3,  and 4.
5.   Open high side bleed
    needle  valve on test kit
    bleeding the air from the
    high  hose. Close the high
    side bleed needle valve.
6.   Open low side bleed
    needle  valve on test kit
    bleeding the air from the
    low hose. Close the low
    side bleed needle valve.
7.   The differential gauge
    pressure should read a
    minimum of 1 psid.
8~  Open the high side
    control needle valve and
    the by-pass hose control
    needle  valve on the test
    kit. (This supplies high
    pressure water
    downstream of check
    valve number 2).
9.   Close test cock number 2.
    (This stops the supply of
    any high pressure water
    downstream of number 2
    check valve). If the
    differential pressure
    gauge holds steady, the
    number 2 shut-off valve is
    recorded as being tight. If
    the differential pressure
    gauge drops to zero, the
    number 2 shut-off valve
    is recorded as leaking.
  With a leaking number 2
shut-off valve, the device is,
in most cases, in a flow
condition, and the previous
test readings taken are
invalid. Unless a non-flow
condition can be achieved,
either through the operation
of an additional shut-off
downstream,  or the use of a
temporary compensating
by-pass hose, accurate test
results will not be achieved.
  This completes the
standard field test for a
double check valve assembly.
Prior to removal of the test
equipment, the tester should
insure that he opens number
2 shut-off valve thereby
reestablishing flow. All test
data should be recorded on
appropriate forms and the
test kit drained of water.

         Duplex gage
                          Individual Bourdon gages mounted on a board
                   bypass hose
 High side hose/   \Low :
side hose
Method 2
Utilizing "Duplex Gauge" or
individual bourdon gauges, -
requires closing number 1
shut-off.   (Figure 42)

Step 1 checking check valve
number 1
1.  Connect the high hose to
    test cock number 2.
2.  Connect the low hose to
    test cock number 3.
3.  Open test cocks number
    2 and number 3.
4.  Close number 2 shut-off
    valve; then close number
    1 shut-off valve.
5.  By means of the high
    side needle valve, lower
    the pressure at test cock
    number  2 about 2 psi
    below the pressure at test
    cock  number 3. If this
    small difference can be
    maintained, then check
    valve number 1 is
    reported as "tight".
    Proceed  to Step number
    2. If the  small difference
    cannot be maintained,
    proceed  to Step number
                              High side hose
                         Low side hose
           Step 2 checking check valve
           number 2.
             Proceed exactly the same
           test procedure as in Step
           number 1, except that the
           high hose is connected to test
           cock number 3 and the low
           hose connected to test cock
           number 4.
Step 3
1.   Open shut-off valve
    number 1 to repressurize
    the assembly.
    Loosely attach the
    by-pass hose to test cock
    number 1, and bleed
    from the gauge through
    the by-pass hose by
    opening the low side
    needle valve to eliminate
    trapped air. Close low
    side needle valve.
    Tighten by-pass hose.
    Open test cock number 1.

    Close number 1 shut-off
    By loosening the  low side
    hose at test cock number
    3, lower the pressure in
    the assembly about 10 psi
    below normal line
    Simultaneously open
    both needle valves  . If the
    check valve is holding
    tight the high pressure
    gauge will begin to drop
    while the low pressue
    gauge will increase. Close
    needle valves. If the
    gauge shows that a small
    (no more than 5 psi)
    backpressure is created
    and held, then the  check
    valve is reported  as tight.
    If the check valve leaks, a
    pressure differential is
    not maintained as both
    gauges tend to equalize
    or move back towards
    each other, then the
    check valve is reported as
    leaking. With both  needle
    valves open enough to
    keep the needles  on the
    gauge stationary,  the
    amount of leakage is
    visable as the discharge
    from the upstream needle

Chapter Six
Administration  of
A  Cross-Connection
      FIGURE 43
Air conditioning cooling tower
        ReducJd pressure zone
        backfldlv preventer
             acKriow p
             with inter
             Laboratory faucet double
             check valve with
             intermediate vacuum breaker
             vacuum breaker
             Hose vacuum breaker
             Reduced pressure zone
             backflow preventer
                  Containment device
   Under the provisions of
   the Safe Drinking Water
Act of 1974, the Federal
Government has established,
through the EPA
(Environmental Protection
Agency), national standards
of safe drinking water. The
states are responsible for the
enforcement of these
standards as well as the
supervision of public water
supply systems and the
sources of drinking water.
The water purveyor
(supplier) is held responsible
for compliance to the
provisions of the Safe
Drinking Water Act, to
include a warranty that water
quality provided by his
operation is in conformance
with the EPA standards at
the source, and is delivered
to the customer without the
quality being compromised
as a result of its delivery
through the distribution
system. As specified in the
Code of Federal Regulations
(Volume 40, Paragraph 141.2,
Section (c)) "Maximum
contaminant level, means the
maximum permissable level
of a contaminant in water
which is delivered to the free
flowing outlet of the ultimate
user of a public water
system, except in the case  of
turbidity where the
maximum permissable level
is measured at the point of
entry to the distribution
system. Contaminants added
to the water under
circumstances controlled by
the user, except those
resulting from corrosion of
piping and plumbing caused
by water quality,  are
excluded from this
  Figure 43 depicts several
options that are open to a
water purveyor when
considering cross-connectio
protection to commercial,
industrial, and residential
customers. He may elect to
work initially on the
"containment" theory. This
approach utilizes a minimui
of backflow devices and
isolates the customer from
the water main. It  virtually
insulates the customer from
potentially contaminating 01
polluting the public water
supply system. While it is
recognized that
"containment" does not
protect the customer within
his building, it does
effectively remove him from
possible contamination to tr
public water supply  system.
If the water purveyor elects
to protect his customers on
domestic  internal protective
basis and/or "fixture outlet
protective basis," then
cross-connection control
protective devices  are placec
at internal high hazard
locations  as well as at all
locations  where
cross-connections  exist at th
"last free-flowing outlet."
This approach entails
extensive cross-connective
survey work on behalf of the
water superintendent as wel
as constant policing of the
plumbing within each
commercial, industrial and
residential account. In large
water supply systems, fixtur
outlet protection
cross-connection control
philosophy, in itself, is a
virtual impossibility to
achieve and police due to th
quantity of systems involved
the complexity of the
plumbing systems  inherent i
many industrial sites, and  th
fact that many plumbing
changes are made  within
industrial and commercial
establishments that do not
require the water department
to license or otherwise
endorse or ratify when
contemplated or completed.

                                                            Method of Action
In addition, internal
plumbing cross-connection
control survey work is
generally foreign to the
average water purveyor and
is not normally a portion of
his job description or duties.
While it is admirable for the
water purveyor to accept and
perform  survey work, he
should be aware that he runs
the risk of additional liability
in an area that may be in
conflict with plumbing
inspectors, maintenance
personnel and other public
health officials.
  Even where extensive
"fixture outlet protection,"
cross-connection control
programs are in effect
through the efforts of an
agressive and thorough water
supply cross-connection
control program, the water
authorities should also have
an active "containment"
program in order to address
the many plumbing changes
that are made and that are
inherent within commercial
and industrial
establishments. In essence,
fixture outlet protection
becomes an extension beyond
the "containment" program.
  Also, in order for the
supplier of water to provide
maximum protection of the
water distribution system,
consideration should be
given to  requiring the owner
of a premise (commercial,
industrial, or residential) to
provide at his own expense,
adequate proof that  his
internal water system
complies with the local or
state plumbing code(s). In
addition, he may be required
to install, have tested, and
maintain, all backflow
protection devices that would
be required — at his own
  The supplier of water
should have the right of entry
to determine degree of hazard
and the existence of
cross-connections in order to
protect the potable  water
system. By so doing he can
assess the overall nature of
the facility and its potential
impact on the water system
(determine degree of hazard),
personally see actual
cross-connections that could
contaminate the water
system, and take appropriate
action to insure  the
elimination of the
cross-connection or the
installation of required
backflow devices.
  To assist the water
purveyor in the total
administration of a
cross-connection control
program requires that all
public health officials,
plumbing inspectors,
building managers,  plumbing
installers, and maintenance
men participate and share in
the responsibility to protect
the public health and safety
of individuals from
cross-connections and
contamination or pollution of
the public water supply
A     complete cross-
     connection control
 program requires a carefully
 planned and executed initial
 action plan followed by
 aggressive implementation and
 constant follow-up. Proper
 staffing and education of
 personnel is a requirement to
 insure that an effective
 program is achieved. A
 recommended plan of action
 for a cross-connection control
 program should include the
 following characteristics:
 (1) Establish a
 cross-connection control
 ordinance at the local level
 and have it approved by the
 water commissioners, town
 manager,  etc., and insure that
 it is adopted by the town or
 private water authority as a
 legally enforceable document.

 (2) Conduct public
 informative meetings that
 define the proposed
 cross-connection control
 program, review the local
 cross-connection control
 ordinance, and answer all
 questions that may arise
 concerning the reason for the
 program, why and how the
 survey will be conducted,
 and the potential impact
 upon the industrial,
 commercial and residential
 water customers. Have state
 authorities and the local
 press and radio attend the
 (3) Place written notices of
 the pending cross-connection
 control program in the local
 newspaper, and have the
 local radio station make
 announcements about the
 program as a public service
 (4) Send employees who will
 administer the program, to a
 course, or courses, on
backflow tester certification,
backflow survey courses,
backflow device repair
courses, etc.
(5) Equip the water authority
with backflow device test

(6) Conduct meeting(s) with
the local plumbing
inspection people, building
inspectors, and licensed
plumbers in the area who
will be active in the
inspection, installations and
repair of backflow devices.
Inform them of the intent of
the program and the part that
they can play in the
successful implementation of
the program.
(7) Prior to initiating a survey
of the established commercial
and industrial installations,
prepare a list of these
establishments from existing
records, then prioritize the
degree of hazard that they
present to the water system,
i.e., plating plants, hospitals,
car wash facilities, industrial
metal finishing and
fabrication, mortuaries, etc.
These will be the initial
facilities inspected for
cross-connections and will be
followed by less hazardous
(8) Insure that any new
construction plans are
reviewed by the water
authority to assess the degree
of hazard and insure that the
proper backflow preventer is
installed concurrent with the
potential degree of hazard
that the facility presents.
(9) Establish a residential
backflow protection program
that will automatically insure
that a residential dual check
backflow device is installed
automatically at every new
(10) As water meters are
repaired or replaced at
residences, insure that a
residential dual check
backflow preventer is set
with the new or reworked
water meter. Be sure to have
the owner address thermal
expansion provisions.

(11) Prepare a listing of all
testable backflow devices in
the community and insure
that they are tested by
certified test personnel at the
time intervals consistent with
the local cross-connection
control ordinance.
(12) Prepare and submit
testing documentation of
backflow devices to the State
authority responsible for
monitoring this data.
(13) Survey all commercial
and industrial facilities and
require appropriate backflow
protection based upon the
containment philosophy
and/or internal protection
and fixture outlet protection.
Follow up to insure that the
recommended devices are
installed and tested on both
an initial basis and a periodic
basis consistent with the
cross-connection control
  The surveys should be
conducted by personnel
experienced in commercial
and industrial processes. The
owners or owners
representatives, should be
questioned as to what the
water is being used  for in the
facility and what hazards the
operations may present to the
water system (both within
the facility and to the water
distribution system) in the
event that a back-siphonage
or backpressure condition
were to  exist concurrent with
a non-protected
cross-connection. In the
event that experienced
survey personnel are not
available within the water
authority to conduct the
survey, consideration should
be given to having a
consulting firm perform the
survey on behalf of the water
                              Control  Survey
   Cross-connection control
   survey work should only
be performed by personnel
knowledgable about
commercial and industrial
potential cross-connections
as well as general industrial
uses for both potable and
process water. If
"containment" is the prime
objective of the survey, then
only sufficient time need be
spent in the facility to
determine the degree of
hazard inherent within the
facility or operation. Once
this is determined, a
judgement can be made by
the cross-connection control
inspector as to what type of
backflow protective device
will be needed at the potable
supply entrance, or
immediately downstream of
the water meter. In the event
that the cross-connection
control program requires
"total" protection to the last
free flowing outlet, then the
survey must be conducted in
depth to visually inspect for
all cross-connections within
the facility and make
recommendations and
requirements for fixture
outlet protective devices,
internal protective devices,
and containment devices.
   It is recommended that
consideration be given to the
following objectives when
performing a
cross-connection control
(1) Determine if the survey
will be conducted with a
pre-arranged appointment or
(2) Upon entry, identify
yourself and the purpose of
the visitation and request to
see the plant manager,
owner, or maintenance
supervisor in order to explain
the purpose of the visit and
why the cross-connection
survey will be of benefit to
(3) Ask what processes are
involved within the facility
and for what purpose potable
water is used, i.e., do the
boilers have chemical
additives? Are air
conditioning cooling towers
in use with chemical
additives? Do they use  water
savers with chemical
additives? Do they have a
second source of water (raw
water from wells, etc.)  in
addition to the potable water
supply? Does the process
water cross-connect with
potentially hazardous
chemical etching tanks, etc.?
(4) Request "as-built"
engineering drawings of the
potable water supply in order
to trace out internal potable
lines and potential areas of
(5) Initiate the survey by
starting at the potable
entrance supply (the water
meter in most cases) and
then proceed with the
internal survey in the event
that  total internal protective
devices and fixture outlet
protective devices are
(6) Survey the plant facilities
with the objective of looking
for cross-connections at all
potable water outlets such as:

  Hose bibbs
  Slop sinks
  Wash room facilities
  Cafeteria and kitchens
  Fire protection and Siamese
  Irrigation outlets
  Boiler rooms
  Mechanical rooms
  Laundry facilities (hospitals)
  Production floor
(7) Make a sketch of all area
requiring backflow protectio
(8) Review with the host
what you have found and
explain the findings to him.
Inform him that he will
receive a written report
documenting the findings
together with a written
recommendation for
corrective action. Attempt tc
answer all questions at this
time. Review the findings
with the owner or manager i
time and circumstances
(9) Document all findings
and recommendations prior
to preparing the written
report. Include as many
sketches with the final repo:
as possible and specifically
state the size and generic
type of backflow preventer
required at each
cross-connection found.

Chapter Seven
Ordinance  Provisions
                              The successful promotion
                              of a cross-connection and
                           backflow-connection control
                           program in a municipality
                           will be dependent upon legal
                           authority to conduct such a
                           program. Where a community
                           has adopted a modern
                           plumbing code, such as the
                           National Plumbing Code,
                           ASA A40.8-1955, or
                           subsequent revisions thereof,
                           provisions of the code will
                           govern backflow and
                           cross-connections. It then
                           remains to provide an
                           ordinance that will establish
                           a program of inspection for
                           an elimination of cross- and
                           backflow connections within
                           the community. Frequently
                           authority for such a program
                           may already be possessed by
                           the water department or
                           water authority. In such cases
                           no further document may be
                           needed. A cross-connection
                           control ordinance should
                           have at least three basic
                           1. Authority for
                           establishment of a program.
                           2. Technical provisions
                           relating to eliminating
                           backflow and
                           3. Penalty provisions for
                             The following model
                           program is suggested for
                           municipalities who desire to
                           adopt a cross-connection
                           control ordinance.
                           Communities adopting
                           ordinances should check
                           with State health officials to
                           assure conformance with
                           State codes. The form of the
                           ordinance should comply
                           with local legal requirements
                           and receive legal adoption
                           from the community.
               MODEL PROGRAM


            Water Department Name
        Cross-Connection Control Program

I. Purpose
  A. To protect the public potable water supply
served by the (      ) Water Department from the
possibility of contamination or pollution by isolating,
within its customers internal distribution system,
such contaminants or pollutants which could
backflow or back-siphon into the public water system.

  B. To promote the elimination or control of existing
cross-connections, actual or potential, between its
customers in-plant potable water system, and
non-potable systems.
  C. To provide for the maintenance of a continuing
program of cross-connection control which will
effectively prevent the contamination or pollution of
all potable water systems by cross-connection.

II. Authority
  A. The Federal Safe Drinking Water Act of 1974,
and the statutes of the State of (     ) Chapters
(      ) the water purveyor has the primary
responsibility for preventing water from unapproved
sources, or  any other substances,  from entering the
public potable water system.
  B. (      ) Water Department, Rules and
Regulations, adopted

    III. Responsibility
      The Director of Municipal Services shall be
    responsible for the protection of the public potable
    water distribution system from contamination or
    pollution due to the backflow  or back-siphonage of
    contaminants or pollutants through the water service
    connection. If, in the judgement of the Director of
    Municipal Services,  an approved backflow device is
    required at the city's water service connection to any
    customer's premises, the Director, or his delegated
    agent, shall give notice in writing to  said customer to
    install an approved backflow prevention device at
    each service connection to  his premises. The
    customer shall, within 90 days install such approved
    device, or devices, at his own expense, and failure or
    refusal, or inability on the part of the customer to
    install said device or devices within  ninety (90) days,
    shall constitute a ground for discontinuing water
    service to the premises until such device or devices
    have been properly installed.

    IV. Definitions
      A. Approved
         Accepted by the Director of Municipal Services
    as meeting an applicable specification stated or cited
    in this regulation, or as suitable for the proposed use.
      B. Auxiliary Water Supply
         Any water supply, on or available, to  the
    premises other than  the purveyor's approved public
    potable water supply.
      C. Backflow
         The flow of water or other liquids, mixtures or
    substances, under positive  or reduced pressure in the
    distribution pipes of a potable water supply  from any
    source other than its intended source.
      D. Backflow Preventer
         A device  or means designed to prevent backflow
    or back-siphonage. Most commonly categorized as
    air gap, reduced pressure principle device, double
    check valve assembly, pressure vacuum breaker,
    atmospheric vacuum breaker, hose bibb vacuum
    breaker, residential dual check, double check with
    intermediate atmospheric vent, and barometric loop.
      D.I Air Gap
         A physical separation sufficient  to prevent
    backflow between the free-flowing discharge end of
    the potable water system and any other system.
    Physically defined as a distance equal to twice the
    diameter of the supply side pipe diameter but never
    less than one  (1) inch.
      D.2 Atmospheric Vacuum Breaker
         A device  which prevents back-siphonage by
    creating an atmospheric vent when there is either a
    negative pressure or sub-atmospheric pressure in a
    water system.
      D.3 Barometric Loop
         A fabricated piping arrangement rising at least
    thirty five (35) feet at its topmost point above the
    highest fixture it supplies.  It is utilized in water
    supply systems to protect against back-siphonage.
  D.4 Double Check Valve Assembly
    An assembly of two (2) independently operating
spring loaded check valves with tightly closing shut
off valves on each side of the check valves, plus
properly located test cocks for the testing of each
check valve.
  D.5 Double Check Valve with Intermediate
Atmospheric Vent
    A  device having two (2) spring loaded check
valves separated by an atmospheric vent chamber.
  D.6 Hose Bibb Vacuum Breaker
    A  device which is permanently attached to a
hose bibb and which acts as an  atmospheric vacuum
  D.7 Pressure Vacuum Breaker
    A  device containing one or  two independently
operated spring loaded check valves and an
independently operated spring loaded air inlet valve
located on the discharge side of the  check or checks.
Device includes tightly closing shut-off valves on
each side of the check valves and properly located
test cocks for the testing of the check valve(s).
  D.8 Reduced Pressure Principle Backflow Preventer
    An assembly consisting of two (2) independently
operating approved check valves with an
automatically operating differential relief valve
located between the two (2) check valves, tightly
closing shut-off valves on each side  of the check
valves plus properly  located test cocks for the testing
of the check valves and the relief valve.
  D.9 Residential Dual Check
    An assembly of two (2) spring loaded,
independently operating check valves without tightly
closing shut-off valves and test cocks. Generally
employed immediately downstream of the water
meter to act as a containment device.
  E. Backpressure
    A  condition in which the owners system pressure
is greater than the suppliers system pressure.
  F. Back-siphonage
    The flow of water or other liquids, mixtures or
substances into the distribution pipes of a potable
water supply system from any source other than its
intended source  caused by the sudden reduction of
pressure  in the potable water supply system.
  G. Commission
                      ) Water Supply and Pollution
    The State of (
Control Commission.
  H. Containment
    A method of backflow prevention which requires
a backflow prevention preventer at the water service
  I. Contaminant
    A substance that will impair the quality of the
water to a degree that it creates a serious health
hazard to the public leading to poisoning or the
spread of disease.
  J. Cross-connection
    Any actual or potential connection between the
public water supply and a source of contamination or

  K. Department
    City of (      ) Water Department.
  L. Fixture Isolation
    A method of backflow prevention in which a
backflow preventer is located to correct a cross
connection at an in-plant location rather than at a
water service entrance.
  M. Owner
    Any person who has legal title to, or license to
operate or habitat in, a property upon which a
cross-connection inspection is to be made or upon
which a cross-connection is present.
  N. Person
    Any individual, partnership, company, public or
private corporation, political subdivision or agency of
the State Department, agency or instrumentality or
the United States or any other legal entity.
  O. Permit
    A document issued by the Department which
allows the use of a backflow preventer.
  P. Pollutant
    A foreign substance, that if permitted to get into
the public water system, will degrade its quality so as
to constitute a moderate hazard, or impair the
usefulness or quality of the water to a degree which
does not create an actual hazard to the public health
but which does adversely and unreasonably effect
such water for domestic use.
  Q. Water Service Entrance
    That point in the owners water system beyond
the sanitary control of the District;  generally
considered to be the outlet end of the water meter
and always before any unprotected branch.
  R. Director of Municipal Services
    The Director, or his delegated representative in
charge of the (    ) Department of Municipal Services,
is invested with the authority and responsibility for
the implementation of a cross-connection control
program and for the enforcement of the  provisions of
the Ordinance.

V. Administration
  A. The Department will operate a cross-connection
control program, to include the keeping of necessary
records, which  fulfills the requirements of the
Commission's Cross-Connection Regulations and is
approved by the Commission.
  B. The Owner shall allow  his property to be
inspected for possible cross-connections and shall
follow the provisions of the  Department's program
and the Commission's Regulations if a
cross-connection is permitted.
  C. If the Department requires that the  public  supply
be protected by containment, the Owner shall be
responsible for water quality beyond the outlet end of
the containment device  and  should utilize fixture
outlet protection for that purpose.
  He may utilize public health officials, or personnel
from the Department, or their delegated
representatives, to assist him in the survey of his
facilities and to assist him in the selection of proper
fixture outlet devices, and the proper installation of
these devices.
VI. Requirements
  A. Department
    1. On new installations, the Department will
provide on-site evaluation and/or inspection of plans
in order to determine the type of backflow preventer,
if any, that will be required, will issue permit, and
perform inspection and testing. In any case, a
minimum of a dual check valve will be required in
any new construction.
    2. For premises existing prior to the start of this
program, the Department will perform evaluations
and inspections of plans and/or premises and inform
the owner by letter of any corrective action deemed
necessary, the method of achieving the correction,
and the time allowed for the  correction to be made.
Ordinarily, ninety (90) days will be allowed,
however, this time period may  be shortened
depending upon the degree of hazard involved and
the history of the device(s) in question.
    3. The Department will not allow any
cross-connection to remain unless it  is protected by
an approved backflow preventer for which a permit
has been issued and which will be regularly tested to
insure satisfactory operation.
    4. The Department shall  inform the Owner by
letter, of any failure to comply, by the time of the first
re-inspection. The Department will allow an
additional fifteen (15) days for the correction. In the
event the Owner fails to  comply with the necessary
correction by the time of the  second  re-inspection, the
Department will inform the Owner by letter, that the
water service to the Owner's  permises will be
terminated within a period not  to exceed five (5)
days. In the event that the Owner informs the
Department of extenuating circumstances as to why
the correction has not been made, a time  extension
may be granted by the Department but in no case  will
exceed an additional thirty (30) days.
    5. If the Department determines at any time that
a serious threat to the public  health exists, the water
service will be terminated immediately.
    6. The Department shall have on file, a list of
Private Contractors  who are certified backflow device
testers. All charges for these tests will be  paid by the
Owner of the building or property.
    7. The Department will begin initial premise
inspections to determine the nature of existing or
potential hazards, following the approval of this
program by the Commission,  during the calendar year
(       ). Initial focus will be  on high hazard
industries and commercial premises.
  B. Owner
    1. The Owner shall be responsible for the
elimination or protection of all  cross-connections on
his  premises.
    2. The Owner, after having  been  informed by  a
letter from the Department, shall at his expense,
install, maintain,  and test, or  have tested, any and all
backflow preventers on his premises.
    3. The Owner shall correct  any malfunction of
the  backflow preventer which is revealed by periodic

    4. The Owner shall inform the Department of any
proposed or modified cross-connections and also any
existing cross-connections of which the Owner is
aware but has not been found by the Department
    5. The Owner shall not install a by-pass around
any backflow preventer unless there is a backflow
preventer of the same type on the bypass. Owners
who cannot  shut down operation for testing of the
device(s) must supply additional devices necessary to
allow testing to take place. (Ref. Fig. 33 page 23.)
    6. The Owner shall install backflow preventers in
a manner approved by the Department. (Ref. Figures 3
through 37, pages 23 through 24.)
    7. The Owner shall install only backflow
preventers approved by the Department or the
    8. Any Owner having a private well or other
private water source, must have a permit if the well
or source is  cross-connected to the Department's
system.  Permission to cross-connect may be denied
by the Department. The Owner may be required to
install a backflow preventer at the service entrance if
a private water source is maintained, even if it is not
cross-connected to the Department's system.
    9, In the event the Owner installs plumbing to
provide potable water for domestic purposes which is
on the Department's side of the  backflow preventer,
such plumbing must have its own backflow preventer
    10 The Owner shall be responsible for the
payment of all fees for permits,  annual or
semi-annual device testing, re-testing in the case that
the device fails to operate correctly, and second
re-inspections for non-compliance with Department or
Commission requirements.

VII. Degree of Hazard
  The Department recognizes the threat to the public
water system arising from cross-connections. All
threats will be classified by degree of hazard and will
require  the installation of approved reduced pressure
principle backflow prevention devices or double
check valves.
VIII. Permits
  The Department shall not permit a cross-connection
within the public water supply system unless it is
considered necessary and that it cannot be
  A. Cross-connection permits that are required for
each backflow prevention device are obtained from
the Department. A fee of (  )  dollars will be charged
for the initial permit and (  ) dollars for the renewal
of each permit.
  B. Permits shall be renewed every  (  ) years and
are non-transferable. Permits are subject to revocation
and become immediately revoked if the Owner
should so change the type of cross-connection or
degree of hazard associated with the service.
  C. A permit is not required when fixture isolation
is achieved with the utilization of a non-testable
backflow preventer.

IX. Existing in-use backflow prevention devices.
  Any existing backflow preventer shall be allowed
by the Department to continue in service unless the
degree of hazard is such as to supercede the
effectiveness of the present backflow preventer, or
result in an unreasonable risk to the  public health.
Where the degree of hazard has increased, as in the
case of a residential installation converting to a
business  establishment, any existing backflow
preventer must be upgraded to a reduced pressure
principle device,  or a reduced pressure principle
device must be installed in the event that no
backflow device was present.

X. Periodic Testing
  A. Reduced pressure principle backflow devices
shall be tested and inspected  at least semi-annually.
  B. Periodic testing shall be  performed by the
Department's certified tester or his delegated
representative. This testing will be done at the
owners's expense.
  C. The testing shall be conducted during the
Department's regular business hours. Exceptions to
this, when at the  request of the owner, may require
additional charges to cover the increased costs to the
  D. Any backflow preventer which fails during a
periodic test will  be repaired  or replaced. When
repairs are necessary, upon completion of the repair
the device will be re-tested at owners expense to
insure correct operation. High hazard situations will
not be allowed to continue unprotected if the
backflow preventer fails the test and cannot be
repaired immediately. In other situations, a
compliance date of not more than thirty (30) days after
the test date will  be established. The owner is
responsible for spare parts, repair tools, or a
replacement device. Parallel installation of two (2)
devices is an effective means  of the owner insuring
that uninterrupted water service during testing or
repair of devices and is strongly recommended when
the owner desires such  continuity. (Ref. Fig. 33 page

  E. Backflow prevention devices will be tested more
frequently than specified in A. above, in cases where
there is a history of test failures and the Department
feels that due to the degree of hazard involved,
additional testing is warranted. Cost of the additional
tests will be born by the owner.

XI. Records and Reports
  A. Records                                     v
    The Department will initiate and maintain the
    1.  Master files on customer cross-connection tests
and/or inspections.
    2.  Master files on cross-connection permits.
    3.  Copies of permits and  permit applications.
    4.  Copies of lists and summaries supplied to the
  B. Reports
    The Department will submit the following to the
    1.  Initial listing of low hazard cross-connections
to the  State.
    2.  Initial listing of high hazard cross-connections
to the  State.
    3.  Annual update lists  of items 1 and 2 above.
    4.  Annual summary of cross-connection
inspections to the State.

XII. Fees and Charges
  The  Department will publish a list of fees or
charges for the following services or permits:
    1.  Testing fees
    2.  Re-testing fees
    3.  Fee for re-inspection
    4.  Charges for after-hours inspections or tests.
1. Residential dual check
  Effective the date of the acceptance of this
Cross-Connection Control Program for the Town of
(      ) all new residential buildings will be required
to install a residential dual check device immediately
downstream of the water meter. (Ref. Figure 3 7
page 24.) Installation of this residential dual check
device on a retrofit basis on existing service lines will
be instituted at a time and at a potential cost  to the
homeowner as deemed necessary by the Department.
  The owner must be aware that installation of a
residential dual check valve results in a potential
closed plumbing system within his residence. As
such, provisions may have to be made by the owner
to provide for thermal expansion within his closed
loop system,  i.e., the installation of thermal expansion
devices and/or pressure relief valves.

2. Strainers
  The Department strongly recommends that  all new
retrofit installations of reduced pressure principle
devices and double check valve backflow preventers
include the installation of strainers located
immediately upstream of the backflow device. The
installation of strainers will  preclude the fouling of
backflow devices due to both foreseen and unforeseen
circumstances occurring to the water supply system
such as water  main repairs, water main breaks, fires,
periodic cleaning and flushing of mains, etc. These
occurrences may "stir up" debris withing the water
main that will cause fouling of backflow devices
installed without the benefit of strainers.

 Appendix A
Appendix  B
 Partial List of
 Plumbing Hazards
 Illustrations of
Fixtures With Direct
Air conditioning, air washer
Air conditioning, chilled water
Air conditioning, condenser water
Air line
Aspirator, laboratory
Aspirator, medical
Aspirator, weedicide and fertilizer sprayer
Autoclave and sterilizer
Auxiliary system, industrial
Auxiliary system, surface water
Auxiliary system, unapproved well supply
Boiler system
Chemical feeder, pot-type
Coffee urn
Cooling system
Fire standpipe or sprinkler system
Fountain, ornamental
Hydraulic equipment
Laboratory equipment
Lubrication, pump bearings
Photostat equipment
Plumber's friend, pneumatic
Pump,  pneumatic ejector
Pump,  prime line
Pump,  water operated ejector
Sewer, sanitary
Sewer, storm
Swimming pool

Fixtures With Submerged
Baptismal fount
Bedpan washer, flushing rim
Brine tank
Cooling tower
Drinking fountain
Floor drain, flushing rim
Garbage can washer
Ice maker
Laboratory sink, serrated nozzle
Laundry machine
Lawn sprinkler system
Photo laboratory sink
Sewer flushing manhole
Slop sink, flushing rim
Slop sink, threaded supply
Steam table
Urinal, siphon jet blowout
Vegetable peeler
Water closet, flush tank, ball cock
Water closet, flush valve, siphon jet
The following illustrates typical
plumbing installations where
backsiphonage is possible.
Case 1 (Fig. 44)
A. Contact Point: A rubber hose
is submerged in a bedpan wash
B. Causes of Reversed Flow: (1)
A sterilizer connected to the
water supply is allowed to cool
without opening the air vent. As
it cools, the pressure within the
sealed sterilizer drops below
atmospheric producing a
vacuum which draws the
polluted water into the sterilizer
contaminating its contents.  (2)
The flushing of several flush
valve toilets on a lower floor
which are connected to an
undersized water service line
reduces the pressure at the  water
closets to atmospheric producing
a reversal of the flow. C.
Suggested Correction: The water
connection at the bedpan wash
sink and the sterilizer should be
provided with properly installed
backflow preventers.
Case 2 (Fig. 45)
A. Contact Point: A rubber ho
is submerged in a laboratory
B. Cause of Reversed Flow: T'
opposite multi-story buildings
connected to the same water
main, which often lacks
adequate pressure. The buildii
on the right has installed a
booster pump. When the
pressure is inadequate in the
main, the building booster pui
starts pumping, producing a
negative pressure in the main
and causing a reversal of flow
the opposite building.
C. Suggested Correction: The
laboratory sink water outlet
should be provided with a
vacuum breaker. The water
service line to the booster pun
should be equipped with a
device to cut off the pump wh
pressure approaches a negativ
head or vacuum.
                                FIGURE 45
                                Backsiphonage - Case 2.
Backsiphonage - case 1.

Case 3 (Fig. 46)
A. Contact Point: A chemical
tank has a submerged inlet.
B. Cause of Reversed Flow: The
plant fire pump draws suction
directly from the city water
supply line which is insufficient
to serve normal plant
requirements and a major fire at
the same time. During a fire
emergency, reversed flow may
occur within the plant.
C. Suggested Correction: The
water service to the chemical
tank should be provided through
an airgap.
Backsiphonage - case 3.
Case 4 (Fig. 47)
A. Contact Point: The water
supply to the dishwasher is not
protected by a vacuum breaker.
Also, the dishwasher has a solid
waste connection to the sewer.
B. Cause of Reversed Flow: The
undersized main serving the
building is subject to reduced
pressures, and therefore only the
first two floors of the building
are supplied directly with city
pressure. The upper floors are
served from a booster pump
drawing suction directly from
the water service line. During
periods of low city pressure, the
booster pump suction creates
negative pressures in the low
system, thereby reversing the
C. Suggested Correction: The
dishwasher hot and cold water
should be supplied through an
airgap and the waste from the
dishwasher should discharge
through an indirect waste. The
booster pump should be
equipped with a low-pressure
cutoff device.
Case 5 (Fig. 48)
A. Contact Point: The gasoline
storage tank is maintained full
and under pressure by means of
a direct connection to the city
water distribution system.
B. Cause of Reversed Flow:
Gasoline may enter the
distribution system by gravity or
by siphonage  in the event of a
leak or break in the water main.
C. Suggested Correction: A
reduced pressure principle
backflow preventer should be
installed in the line to the
gasoline storage tank  or a surge
tank and pump should be
provided in that line.
                                                                                                  FIGURE 48
                                                                                                  Backsiphonage - Case 5.
                                 Case 6 (Fig. 49)
                                 A. Contact Point: There is a
                                 submerged inlet in the second
                                 floor bathtub.
                                 B. Cause of Reversed Flow: An
                                 automobile breaks a nearby fire
                                 hydrant causing a rush of water
                                 and a negative pressure in the
                                 service line to the house,
                                 sucking dirty water out of the
                                 C. Suggested Correction:  The hot
                                 and cold water inlets to the
                                 bathtub should be above the rim
                                 of the tub.
                                                                                                 FIGURE 49
                                                                                                 Backsiphonage - Case 6.
                                FIGURE 47
                                Backsiphonage - case 4.

Appendix  C

Illustrations of
The following presents
illustrations of typical plumbing
installations where backflow
resulting from backpressure is
Case 1 (Fig. 50)

A. Contact Point: A direct
connection from the city supply
to the boiler exists as a safety
measure and for filling the
system. The boiler water system
is chemically treated for  scale
prevention and corrosion
B. Cause of Reversed Flow: The
boiler water recirculation pump
dishcharge pressure or
backpressure from the boiler
exceeds the city water pressure
and the chemically treated water
is pumped into the domestic
system through an open or leaky
C. Suggested Correction: As
minimum  protection two check
valves in series should be
provided in the makeup
waterline to the boiler system.
An airgap  separation or reduced
pressure principle backflow
preventer is better.
                                 Case 2 (Fig. 51)
                                 A. Contact Point: Sewage
                                 seeping from a residential
                                 cesspool pollutes the private
                                 well which is used for lawn
                                 sprinkling. The domestic water
                                 system, which is served from a
                                 city main, is connected to the
                                 well supply by means of a valve.
                                 The purpose of the connection
                                 may be to prime the well supply
                                 for emergency domestic use.
                                 B. Cause of Reversed Flow:
                                 During periods of low city water
                                 pressure, possibly when lawn
                                 sprinkling is at its peak, the well
                                 pump discharge pressure
                                 exceeds that of the city main and
                                 well water is pumped into the
                                 city supply through an open  or
                                 leaky valve.
                                 C. Suggested Correction: The
                                 connection between the well
                                 water and city water should be
                                         FIGURE 51
                                         Backflow - case 2.
Case 3 (Fig. 52)
A. Contact Point: A valve
connection exists between the
potable and the nonpotable
systems aboard the ship.
B. Cause of Reversed Flow:
While the ship is connected to
the city water supply system for
the purpose of taking on water
for the potable system, the valve
between the potable and
nonpotable systems is opened,
permitting contaminated water
to be pumped into the municipa
C. Suggested Correction: Each
pier water outlet should be
protected against backflow. The
main water service to the pier
should also be protected against
backflow by an airgap or
reduced pressure principle
backflow preventer.
Backflow - case 1.
                                                                 Case 4 (Fig. 53)
                                                                 A. Contact Point: A
                                                                 single-valved connection exists
                                                                 between the public, potable
                                                                 water supply and the
                                                                 fire-sprinkler system of a mill.
                                                                 B. Cause of Reversed Flow: The
                                                                 sprinkler system is normally
                                                                 supplied from a nearby lake
                                                                 through  a high-pressure pump.
                                                                 About the lake are large numbers
                                                                 of overflowing septic tanks.
                                                                 When the valve is left open,
                                                                 contaminated lake water can be
                                                                 pumped to the public supply.
                                                                 C. Suggested Correction: The
                                                                 potable water supply to the fire
                                                                 system should be through an
                                                                 airgap or a reduced pressure
                                                                 principle backflow preventer
                                                                 should be used.
                                                                                                 FIGURE 52
                                                                                                 Backflow - case 3.
                                                                                                        ACME MILLS
                                                                                                       Sprinkler system
                                                                                                 FIGURE 53
                                                                                                 Backflow - case 4.

 Appendix  D
                     Appendix E
Illustrations of
                    Illustrations  of
                    Vacuum Breakers
The following illustrations
describe methods of providing
an airgap discharge to a waste
line which may be occasionally
or continuously subject to
 Airgap to sewer subject to
 backpressure - force main.
                                          Ball check
                                        Waste line
                   Brass inset
                                                                     Rubber sleeve
                                                                   Flush connection

                                                                     Cowl nut
                                                       Vacuum closes gate
                                          Air enters here
                                        preventing rise of
                                      contaminated liquids
                                             in fixtures
                                                                                        Air vent
                     FIGURE 57
                     Vacuum breakers
                                      Indirect waste
 Airgap to sewer subject to
 backpressure - gravity drain.
 Ball check

Support vanes
                                Horizontal waste
 Nonpotable supply
Fire system makeup tank for a
dual water system.
'/21' or %" gate valve I
W or %" sch 40 galv
W or %" vacuum bre
'/2"or JA"EII

M 1

1 " sleeve, sch 40,
building wall

I P S hose
r ww
Vi" or %"
nipple galv
Coupling (V
I galv
                     FIGURE 58
                     Vacuum breaker arrangement
                     for an outside hose hydrant.
                     (By permission of Mr Gustave ]. Angele
                     Sr., P.E. Formerly Plant Sanitary
                     Engineer, Union "Carbide Nuclear
                     Division, Oak Ridge, Term )

Appendix  F

Airgap The unobstructed vertical
   distance through the free
   atmosphere between the
   lowest opening from any pipe
   or faucet supplying water to a
   tank, plumbing fixture, or
   other device and the
   flood-level rim of the
Backflow The flow of water or
   other liquids, mixtures, or
   substances into the
   distributing pipes of a potable
   supply of water from any
   source or sources other than
   its intended  source.
   Backsiphonage is one type of
Backflow Connection Any
   arrangement whereby
   backflow can occur.
Backflow Preventer A device or
   means to prevent backflow.
Backflow Preventer, Reduced
   Pressure Principle Type An
   assembly of  differential valves
   and check valves including
   an automatically opened
   spillage port to the
Backsiphonage Backflow
   resulting from negative
   pressures in the  distributing
   pipes of a potable water
Cross-Connection Any actual or
   potential connection between
   the public water supply and
   a source of contamination or
Effective Opening The minimum
   cross-sectional area at the
   point of water supply
   discharge, measured or
   expressed in terms of (1)
   diameter of a circle, or (2) if
   the opening is not circular,
   the diameter of a circle or
   equivalent cross-sectional
Flood-Level Rim The edge of the
   receptacle from which water
Flushometer Valve A device
   which discharges a
   predetermined quantity of
   water to fixtures  for flushing
   purposes and is actuated by
   direct water pressure.
Free Water Surface A water
   surface that is at atmospheric
Frostproof Closet A hopper with
   no water in the bowl and
   with the  trap and water
   supply control valve located
   below frost line.
Indirect Waste Pipe A drain
   pipe used to convey  liquid
   wastes that does not  connect
   directly with the drainage
   system, but which discharges
   into  the drainage system
   through an airbreak into a
   vented trap or a properly
   vented and trapped fixture,
   receptacle, or interceptor.
Plumbing The practice,
   materials, and fixtures used
   in the installation,
   maintenance, extension, and
   alteration of all piping,
   fixtures,  appliances and
   appurtenances in connection
   with any of the following:
   sanitary drainage or  storm
   drainage facilities, the venting
   system and the public or
   private water-supply systems,
   within or adjacent to any
   building, structure, or
   conveyance;  also the practice
   and  materials used in the
   installation, maintenance,
   extension, or alteration of
   storm water, liquid waste, or
   sewerage, and water-supply
   systems of any premises to
   their connection with any
   point of  public disposal or
   other acceptable terminal.
Potable Water Water free from
   impurities present in amounts
   sufficient to cause disease or
   harmful physiological effects.
   Its bacteriological and
   chemical quality shall
   conform to the requirements
   of the Public Health Service
   Drinking Water Standards or
   the regulation of the public
   health authority having
Vacuum  Any absolute pressure
   less than that exerted by the
Vacuum  Breaker A device that
   permits air into a water
   supply distribution line to
   prevent backsiphonage.
Water Outlet A discharge
   opening through which water
   is supplied to a fixture, into
   the atmosphere (except into
   an open tank which is part of
   the water supply system), to a
   boiler or heating system,  to
   any devices or equipment
   requiring water to operate but
   which are not part of the
   plumbing system.
Water Supply System The water
   service pipe, the
   water-distributing pipes,  and
   the necessary connecting
   pipes, fittings, control valves,
   and all appurtenances in  or
   adjacent to the building or
   premises. The water supply
   system is part of the
   plumbing system.

 \ppendix G

 ccepted Procedure and Practice
   in Cross-Connection Control
   ManuaJ, American Water
   Works Association, Pacific
   Northwest Section, 4th
   Edition. Nov.1985.
 merican  Backflow Prevention
   Association, P.O. Box 1563
   Akron,  Ohio 44309-1563.
 ngele, Gustave ].,
   Cross-Connection and
   Backflow Prevention,
   American Water Works
   Association. Supplementary
   Reading library Series -  No.
   S106, New York 10016.
  Revision of The National
   Plumbing Code, ASA
   A40.8-1955, Report of the
   Public Health Service
   Technical Committee on
   Plumbing Standards. Sept. 15,
   1962, Public Health Service,
   Washington 25, D.C.
AWWA Standard For Backflow
   Prevention Devices - Reduced
   Pressure Principle and
   Double Check Valve Types
   (C509-78J, American Water
   Works Association, Denver,
   Colorado, Reaffirmed 1983.
Back/low Prevention and
   Cross-Connection Control,
   AWWA Manual M14,
   American Water Works
   Association, Denver, Colorado
Hack/low Prevention and
   Cross-Connection Control,
   Ohio EPA, Office of Public
   Water Supply. Second
   Edition, Revised Mar.15,1977.

Back/low Prevention Devices -
   Selection, installation,
   Maintenance, and Field
   Testing, CSA Standard
   B64.10M1981. Canadian
   Standards Association,
Back/low - The Manual of
   Cross-Connection Prevention
   in Public Water Supplies,
   Missouri Dept. of Natural
Canadian Plumbing Code 1980.
   NRCC, No.17305, Second
   Printing, Issued by the
   Associate Committee on the
   National Building Code,
   Natural Research Council  of
   Canada, Ottawa.
Control and Elimination of
   Cross-Connections, Panel
   Discussion, Journal American
   Water Works Association,
   Vol.50, No.1,1960.
Cross-Connection Complications,
   The Capital's Health, Vol.11,
   No. 9, Dec.1953, D.C. Dept. of
   Public Health, Washington,
Cross-Connection Control,
   American Water Works
   Association, British Columbia
   Section, Second Edition,
   Jan.1980. Cross-Connection
   Control and Back/low
   Prevention Device Testing,
   New England Water  Works
   Association, August  1987.
Cross-Connection Control and
   Back/low Prevention, Practice
   and Procedure Manual,
   Administrative Manual, City
   of Winnipeg, Manitoba.  Third
   Edition, April 1980.
Cross-Connection Control,
   Backflow Prevention Device
   Tester Certification Training
   Course, Public Drinking
   Water Program, Divison of
   Environmental Quality,
   Department of Natural
   Resources, State of Missouri.
Cross-Connection Control
   Manual, Division of  Sanitary
   Engineering, Tennessee  Dept.
   of Public Health, 1975.
Cross-Connection Control
   Regulation in Washington
   State,  Washington State Dept.
   of Social and Health Services,
   Denver, Colorado, 1974.
   Second Edition.
Cross-Connection Control, New
   York State Dept. of Health,
Cross-Connection Control
   Program, State of Utah,
   Oct.1985, Travis Black.
Cross-Connection Control, Water
   Quality Division, Colorado
   Department of Health.
   Revised March 1983.
Cross-Connection Control
   Survey, New England Water
   Works Association, August
CSA Standards on Vacuum
   Breakers and Back/low
   Preventers, B64 Series 1976
   Canadian Standards
   Association, Dec.1976.
Dawson, F. M., and Kalinske, A.
   A., Report on
   Cross-Connections and
   Backsiphonage Research,
   Technical  Bulletin No.l,
   National Association of
   Plumbing, Heating, Cooling
   Contractors, Washington, D.C.

Evaluation of Back/low
   Prevention Devices - A State
   of the Art, (N B SIR 76-1070)
   U.S.  Environmental
   Protection Agency, Water
   Supply Division, Washington,
   D.C., June  1976.
Hendrickson, Howard D.
   Cross-Connection Control,
   Part 1 & 2, August &
   September 1981 issues of
   Reeves  Journal.
How To Prevent Industrial
   Cross-Connection Dangers,
   Water Works Engineering,
   Feb.1962. Manitoba Plumbing
   Code 1981, Issued by the
   Department of Labour and
   Manpower oi the Province of
Manual of Cross-Connection
   Control, Dept. of Health and
   Hospitals,  Denver, Colorado,
Manual of Cross-Connection
   Control, Foundation for
   Cross-Connection Control and
   Hydraulic  Research,
   University of Southern
   California, 7th Editions, June
Manual of Cross-Connection
   Control Practices and
   Procedures, State of
   California, Health and
   Welfare Agency, July 1981.
Plumbing and Drainage Act
   Regulations, Alberta, As
   amended by Alberta
   Regulations (295/80).
Regulations Relating To
   Cross-Connections,  excerpt
   from the California
   Administrative Code, Title 17,
   Public Health, 1956.
Saskatchewan Regulations 8/78,
   Regulations Governing
   Plumbing and Drainage
Solar Domestic Hot  Water
   Systems and the  Water
   Purveyor, American Water
   Works Association, Pacific
   Northwest Section.
Springer, E. K., and  Reynolds, K.
   C., De/initions and
   Specifications of Double
   Check Valve Assemblies and
   Reduced Pressure Principle
   Back/low Prevention Devices,
   University of Southern
   California, School of
   Engineering Dept. 48-101,
Taylor, F. B., and Skodje, M. T.,
   Cross-Connections,  A Hazard
   in All Buildings,  Modern
   Sanitation and Building
   Maintenance, Vol.14, No.8,
Use of Backflow Preventers for
   Cross-Connection Control,
   Joint Committee Report,
   Journal American Water
   Works Association, Vol. 50,
   No.12, Dec.1958.
Van  Meter, R. O., Backflow
   Prevention Hardware, Water
   and Wastes Engineering, Pt.l,
   Sept.1970; Pt.2, Oct.1970. !

 Appendix  H

 Survey Form

 Name of Company, Corporation, or Business:
 Name of Contact:
 Type of Use:    Industrial

 Location of Service:	

 Size of Service:	
 Require non-interrupted water service?
 Does Boiler Feed utilize chemical additives?
   Is Backflow protection incorporated?
 Are air conditioning cooling towers utilized?
Yes D
                                       Yes D
                                       Yes D
                                       Yes D
                                       Yes D
   Is the make-up supply line backflow protected?
                                       Yes D
No D
                            No D
                            No D
                            No D
                            No D
   Is Backflow protection incorporated?                                     Yes D       No D

 Is a Water Saver utilized on condensing lines or cooling towers?    N/A D      Yes D       No D
                             No D
 Is process water in use, and if so, is it potable supply water or "Raw" water      N/A  D   Potable D

                                                    Raw D     Protected  D    Unprotected D
 Is fire protection water separate from the potable supply?
 Are Containment Devices in place?
                                       Yes D
                                       Yes D
                             No D
                             No D
  Degree of Hazard:
  Type of Device recommended for containment:
  Fixture Outlet protection required?
                                      High  D      Low D
                           RPZ D      DCV D     None D
                                        Yes  D
                             No D
  If so, where?.

 Appendix  I
Backflow  Prevention Device
Test and  Maintenance Report

    (water purveyor or regulatory agency)
Attn: Cross-connection Control Section

The cross-connection control device detailed hereon has been tested and maintained as
required by the (ruJes or regulations] of (purveyor or regulatory agency) and is certified
to comply with these (ruJes or regulations].

  Make of device	
  Model Number

  Serial Number .
located at

Initial Test
Repairs and
Materials Used
After Repair
Reduced Pressure Devices
Double Check Devices
1st check
DC-Closed Tight EH
RP- psid
Leaked [ 	 |

DC-Closed Tight D
RP- psid

2nd check
Closed Tight D
Leaked 1 	 1

Closed Tight D
Relief Valve
Opened at

Opened at

Pressure Vacuum Breaker
Air Inlet
Opened at
Did Not Open

Opened at

Check Valve
Leaked I 	 1


The above is certified to be true.
Firm Name	
Firm Address
Certified Tester.

Cert. Tester No._

4ft T) O

O0" 0.


o   s.
o   -D
         O  0

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