WATER SUPPLY
DIVISION
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CROSS-CONNECTION
CONTROL MANUAL
U.S. Environmental Protection Agency
Office of Water Programs
Water Supply Division
First Printed 1973 Reprinted in 1974,1975
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Price $1
Stock No. 055-001-00614-4/Catalog No. EP 2.8:C88
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PREFACE
Plumbing cross-connections, which connect potable water supply with
nonpotable supply, are a public health problem. There are numerous and
well-documented cases where such connections have been responsible for
contaminated drinking water, and have resulted in spread of disease. The
problem is a dynamic one, because piping systems are continually being
installed, altered, or extended.
Control of cross-connections is possible, but only through knowledge and
vigilance. Education is essential, for many of those who are experienced in
piping installation fail to recognize cross-connection possibilities and dangers.
All municipalities with public water supplies should have cross-connection
control programs. Those responsible for institutional or semipublic water
supplies also should be familiar with the dangers, and should exercise careful
surveillance.
The Cross-Connection Control Manual has been designed as a tool for health
officials, waterworks personnel, plumbers, and many others; it is intended to
be used in educational, administrative, and technical ways in conducting
cross-connection control programs. This manual is a revision of an earlier book
entitled Water Supply and Plumbing Cross-Connections (PHS Publication No.
957), which was produced under the direction of Floyd B. Taylor by Marvin T.
Skodje, who wrote the text and designed the illustrations.
This new edition contains many of the original illustrations and much of the
text. Some figures and all chapters have been clarified and updated and some
extraneous material has been omitted. The work was done by Peter C.
Karalekas, Jr., with guidance from Roger D. Lee; it also incorporates
suggestions made by the staff of the Water Supply Division, other govern-
mental agencies, and interested individuals.
Chapter 2, "Public Health Significance of Cross-Connections," appeared in
Modern Sanitation and Building Maintenance, vol. 14, No. 7 (July 1962).
Permission to reprint has been given. Also, more recent examples of cross-
connection cases have been included at the end of chapter 2.
ill
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CONTENTS
Page
Preface iii
List of Illustrations vi
American Water Works Association Policy on Cross-Connections . . vii
Chapter
1 Purpose and Scope 1
2 Public Health Significance of Cross-Connections 3
3 Theory of Backflow and Backsiphonage 9
4 Methods and Devices for Backflow Prevention 19
5 Testing Procedures for Backflow Preventers 27
6 Administration of a Cross-Connection Control Program 32
7 Cross-Connection Control Ordinance Provisions 35
Appendixes
A Partial List of Plumbing Hazards 43
B Illustrations of Backsiphonage 44
C Illustrations of Backflow 48
D Illustrations of Airgaps 51
E Illustrations of Vacuum Breakers 52
F Glossary 53
G Bibliography 55
H Sample Cross-Connection Survey Form 56
Index 57
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ILLUSTRATIONS
Figure fhge
1 Pressure exerted by 1 foot of water at sea level 10
2 Pressure exerted by 2 feet of water at sea level 11
3 Pressure on the free surface of a liquid at sea level 11
4 Effect of evacuating air from a column 12
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 15
8 Negative pressures created by constricted flow 15
9 Dynamically reduced pipe pressures 16
10 Valved connection between potable water and nonpotable fluid 17
11 Valved connection between potable water and sanitary sewer 17
12 Airgap on lavatory 19
13 Surge tank and booster pump 20
14 Booster system 22
15 Operation of a vacuum breaker 23
16 ^Typical non-pressure-type vacuum breaker installation 24
17 Reduced pressure zone backflow preventer — principle of operation ... 25
18 Pressure-type vacuum breaker installation 28
19 Reduced pressure zone backflow preventer field test 29
20 Method of testing check valves 30
21 Backsiphonage — case 1 44
22 Backsiphonage — case 2 45
23 Backsiphonage — case 3 46
24 Backsiphonage — case 4 47
25 Backsiphonage — case 5 47
26 Backsiphonage — case 6 48
27 Backflow - case 1 48
28 Backflow - case 2 49
29 Backflow - case 3 50
30 Backflow - case 4 50
31 Airgap to sewer subject to backpressure — force main 51
32 Airgap to sewer subject to backpressure — gravity drain 51
33 Fire system makeup tank for a dual water system 52
34 Vacuum breakers 52
35 Vacuum breaker arrangement for an outside hose hydrant 53
VI
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American Water Works Association
POLICY ON CROSS-CONNECTIONS
A statement adopted by Board of Directors on Jan. 26, 1970
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 system.
It is realized that cross-connection control and plumbing inspections on
premises of its customers are regulatory in nature and should be handled
through the rules, regulations, and recommendations of the health authority or
the plumbing-code enforcing agencies having jurisdiction. The water purveyor,
however, should be aware of any situation requiring inspection and/or
re-inspections 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.
vu
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Chapter 1. PURPOSE 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 a 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 device.
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
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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.
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Chapter 2. PUBLIC HEALTH SIGNIFICANCE OF
CROSS-CONNECTIONS
According to the official investigation of the 1933 Chicago epidemic of
amebic dysentery, ". .. old and generally defective plumbing and cross-
connections potentially permitting backsiphonage from fixtures such as bath-
tubs and toilets ..." were to blame for contamination of the drinking water
supply.
The event and its sad result — the death of 98 persons — dramatized the
concern that public health officials feel about the dangers of cross-connections.
Because such plumbing defects are so frequent, and the opportunity for
contaminants to invade drinking water through cross-connections is so general,
enteric infections caused by drinking water may occur in almost any city on
any day.
Published histories of massive enteric infections caused by cross-connections
abound. While the following cases have their natural appeal as historical
literature, they are listed here mainly to illustrate the serious consequences of
cross-connections, their ubiquity, their frequency, and their peculiarity.
Brucellosis at the Faucet
In 1938, 80 students at a large mid western university reported remittent
fevers, malaise, headache, and anemia. Their symptoms led to a diagnosis of
undulant fever (brucellosis). Curiously, only those students who had been
working in the cultivation of bacteria in one of the laboratories were affected.
The mystery was how the brucella cultures in the laboratory could have been
transmitted to the students. Finally, a hose was found connected to a faucet in
the laboratory. The other end of the hose was submerged in water containing
brucella. A temporary reversal of pressure, possibly the consequence of a
demand for water in another part of the system, had drawn the water teeming
with brucella into the drinking supply. Of the 80 students affected, one died.
Sewage in the Water Main
In Newton, Kans., in 1942, one of the town's two water supply mains had
been taken out of service on September 2, 7, and 8. A house service connection
to this main supplied three frostproof hydrants and two frostproof toilets. It
was assumed, from subsequent events, that some unknown person or persons
tried to obtain water from a hydrant connected to the main out of service.
When no water flowed, the anonymous agents departed, leaving the valve open.
On September 10, it was discovered that a neighboring toilet sewer was clogged
and that sewage had overflowed into the hydrant box. It was learned that for 2
days all the sewage from the toilets of 10 families had been permitted to flow
into the water main. When the main was put back into service, there was no
attempt to sterilize it. More than 2,500 persons in all parts of the town
suffered enteric disorders as a result. Stool cultures and pathological findings
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from two autopsies diagnosed the illness as bacillary dysentery. In addition to
the widespread illness in the town, it is believed that the infection was carried
aboard a number of troop trains which were watered in Newton at that time.
Pressure Drop
In 1942 a casting plant in Pittsburgh employing 500 persons undertook to
install new water connections. During installation, the city water supply was
shut off. It is believed that a drop in pressure in the drinking water lines of the
plant permitted river water to pass through a valved connection to the drinking
water. Twelve hours after the first new connection to the city water was
installed, many of the employees suffered mild intestinal disorders. Two weeks
later, after another shutdown to make a second connection from the plant
system to the city water, there was a second outbreak of intestinal disturbances
among the employees.
Defective Valve
Aboard a vessel in a west coast shipyard in 1943, a valve on the main line,
connecting the drinking water to the fire water supply, was found to be
defective and the cause of an outbreak of gastroenteritis. The pumping of
contaminated harbor water through the fire waterlines aboard the vessel had
forced bacteria into the drinking supply through a cross-connection. As a
result, 1,179 men became ill.
Arsenic in Reverse
A California laborer had been using an aspirator, attached to a garden hose,
to spray a driveway with weedkiller containing arsenic. Sometime while he was
at the job, the water pressure reversed. Taking no notice of the incident, the
man disconnected the hose and, feeling thirsty, drank from the bib of the hose
connection at the house. Arsenic in the waterline killed him.
Peak Demands
At a large aviation plant on the west coast, officials learned that the
difference between a 3-inch water main and an 8-inch main was the
determining cause for a high rate of absenteeism. When it was discovered that
25 to 40 percent of the employees were suffering from gastroenteritis, the
plumbing system was suspected. Investigators found that there was such a
demand on the 3-inch main at peak periods that the outflow produced enough
of a vacuum to allow waste water to be backsiphoned through
cross-connections into the drinking water system. After an 8-inch main was
installed, the high rate of infection subsided.
The Vacuum Breaker
In April 1944, after an outbreak of gastroenteritis in an Oklahoma school, it
was found that none of the flushometer valve toilets with submerged inlets
were provided with vacuum breakers, which prevent atmospheric pressure from
forcing waste water into the supply lines. Each night, to conserve water and
eliminate the possibility that rooms might be flooded if a leak should develop,
the custodian turned off the valve of the main supply line. As the pressure in
the supply lines was cut off, atmospheric pressure on the toilet bowls moved
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the waste water up into the drinking supply. Most of the people affected were
those who drank from faucets on the first floor of the school; there were
progressively fewer cases on the second and third floors, as the atmospheric
pressure moved less of the waste water to those heights.
Wrong Valve
At a school in Milford, Nebr., the fire lines and hydrants were separate from
the domestic water supply, although the two systems were connected through
a valve at the pumphouse. The source of water for the fire system was the river.
In January 1947, following a fire, someone negligently opened the connecting
valve at the pumphouse, and river water entered the domestic water supply.
About 150 people came down with gastroenteritis.
Ten-Percent Polio Incidence
In 1932 during a 5-week period, more than 10 percent of the 347 children in
Huskerville, near Lincoln, Nebr., contracted polio. A study of the water supply
revealed that the afflicted children lived in areas where flush valve water closets
lacked vacuum breakers. A time relationship was found also in places where
extreme fluctuations of pressure in the water mains might have permitted
waste water to be forced into the drinking supply.
Dysentery at Sea
In 1952 a large oceangoing vessel set sail from its berth with every indication
that things were shipshape. A day or so later and 300 miles out, over a
thousand cases of dysentery developed among those on board. Contaminated
water was blamed for the episode and the evidence indicated that while tied up
at its moorings, the ship's fresh-water tanks had been contaminated. A
cross-connection was the most likely explanation.
A Drink of Chromates
Chromates are one of the chemicals for which the Public Health Service
Drinking Water Standards prescribe the very low amount of 0.05 parts per
million as the limit that can be tolerated in a drinking water supply. In 1958 an
employee using a drinking water fountain in a large city library noticed that
the water stream issuing from the spout was yellowish, and the matter was
called to the attention of the building engineer. Upon investigation, it was
found that the chilled-water pipe system supplying the fountains was directly
connected to another chilled-water system in which heavy dosages of
chromates were used for corrosion control. Someone forgot to close the valve!
Harbor Water Threatens Vessel Crews
At about 2 p.m. on June 29, 1960, on a large pier installation in an eastern
port harbor, a worker noticed evidence of salt in the potable water supply.
Investigation showed that salt water from the harbor had been pumped into
the pier's potable water pipes. The fire systems of three vessels anchored
nearby had been connected to the fresh water piping system and high
fire-pump pressures apparently did the rest. One measurement of chlorides at a
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"fresh" water outlet showed 6,425 parts per million. Only prompt and
vigorous action by a sanitary engineer is believed to have prevented widespread
illness.
Antifreeze
Usually service stations supply antifreeze for automotive equipment, not for
people to drink. The reverse was true during October of 1961 when there
occurred one of the most bizarre backsiphonage episodes on record. In a
midwestern city, ethylene glycol antifreeze was being pumped from a large
storage tank to an antifreeze distribution system. This system was cross-
connected to the city water supply lines and it was estimated that over 100
gallons of 60 percent ethylene glycol were pumped into the water mains.
Samples from the water pipes showed the presence of from 1.5 to 2.0 percent
ethylene glycol, or up to 20,000 parts per million of this toxic chemical agent.
A homeowner reported a bitter taste and reddish color to the water depart-
ment. Radio announcements, a shutdown of the water supply to the area
affected, and repeated flushings were required to cope with the situation.
Outbreak Fells Shipyard Workers
The time was 7 a.m. on September 28, 1962, at a large eastern shipyard.
Beginning then and throughout the day, some 700 men reported ill with
gastroenteritis. All had drunk water from the yard area where they worked and
one water sample showed coliforms in excess of 240 per 100 milliliters.
Investigators concluded that a temporary cross-connection had been made
between the potable water lines and pipes containing river water for
firefighting purposes. They stated that ". . . such an episode may occur again
if steps are not taken to insure that such ill-considered cross-connections
cannot be made by accident."
The following incidents occurred after the publication of the first edition of
this manual. They show that cross-connection continues to be a serious hazard
to water supplies and only constant vigilance in their detection and elimination
can reduce the ever-present risk of contamination from these sources.
Arsenic Poisoning
On a private farm in Texas in 1963, five people were poisoned with arsenic
from drinking water. The source of drinking water was a cistern. A cotton
defoliant tank which contained arsenic was improperly connected to the
cistern. Backsiphonage occurred, and of the five people who drank the water,
three died.
Nurses 111
Backsiphonage caused by defective plumbing in a new student nurses
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building was blamed for an outbreak of disease in 1963 in Ohio. It was
necessary for 100 of the student nurses to be quarantined for 2 weeks.
Bacteriological examination showed that the drinking water was contaminated.
The city health commissioner theorized that salmonella was brought into the
building by some of the girls and then spread by defective plumbing.
Eleven Vomiting Caddies
Eleven caddies experienced nausea, severe vomiting, and abdominal cramps
after consuming a "soft drink" at a New York golf club in 1964. The beverage
was commercially prepared by the mixture of sirup with carbonated water in a
vending machine. Investigation revealed that a pipe carrying water into the
machine was connected to the recirculating hot water heating system instead of
the drinking water system. The day before the incident a lye and chromate
solution was added to the hot water system.
Raw Water From a Drinking Fountain
A New England town had two separate water systems — one for potable
water, the other for fire protection. The fire protection system pumped
untreated water directly from a river. In 1967, at an industrial plant in town,
workers mistook a fire system line for a fresh-water line and connected a
bubbler to it. After drinking the water from the bubbler, seven people
developed infectious hepatitis and over a hundred people were ill with
gastroenteritis.
Shigellosis
In 1967, an outbreak of gastroenteritis occurred at a small private college in
Pennsylvania. Almost one-quarter of the 700 students and faculty were
affected. The only factor in common to all those who became ill was the
consumption of water or food that had been prepared using water from the
school water system. Investigation of the water system revealed that a water-
line had broken in the kitchen of the school cafeteria flooding both the kitchen
and the cafeteria. Cross-connections were found between the sewage system
and the fresh-water system that could have resulted in backsiphonage of sewage
into the water system as a consequence of negative pressure during the break in
the waterline. It was concluded that the outbreak probably resulted from the
presence of Shigella sonnet in the water system. The inoculum would have been
of sufficient size to overcome the chlorine in the water.
Football Team Stricken
In October 1969, most of the members and coaches of a college varsity
football team became ill with infectious hepatitis. The water supply on the
practice field was found to be the cause. A drinking fountain and the irrigation
system for the field were on the same line. A heavy fire demand in the area had
created a negative pressure in the waterlines and caused contaminated surface
water around the sprinklers to be siphoned into the potable water lines. Players
and coaches drinking from the fountain became ill and the school was forced
to cancel the remainder of the football schedule.
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Temporary Hydrant Connections
A serious emergency involving the contamination of a water supply was
caused by a truck filling from a city water supply. In 1971, a contractor using a
tank truck with a rig designed to pump and spray a mixture of water, fertilizer,
grass seed, and woodpulp was working on the grounds of a-sub division. The
contractor was using a direct connection to a fire hydrant to fill the tank with
water, which was then mixed with the fertilizer, etc. A high-pressure pump
then sprayed the mixture onto the ground. As the woodpulp circulated
through the tank piping system, it plugged one of the lines while the pump
continued to run creating a very high pressure in the tank. This pressure was
higher than the water supply system pressure and it forced the solution of
fertilizer into the water system. Several people in the subdivision became ill
after drinking the water, but the contamination was discovered and quick
action in flushing and disinfecting the lines eliminated the danger.
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Chapter 3. THEORY OF BACKFLOW AND
BACKSIPHONAGE
A cross-connection1 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 link between the two systems. Second, the
resultant for ce must be toward the potable supply.
An understanding of the principles of backflow and backsiphonage 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 (P) 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
or
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 pressure.
The term vacuum indicates that the absolute pressure is less than the atmo-
spheric 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. Backflow,
1 See formal definition in the glossary of the appendix.
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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 tig. 1.) The average weight of a cubic foot of water is 62.4 pounds.
The pressure exerted upon the square foot area is, therefore, 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.
FlGURK 1. Pressure exerted b> I fool of water at sea level.
Suppose another cubic fool of water were placed directly on topol the first,
(Sec fig. 2.) The pressure on the top surface of (lie 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 at the base of the first cube
would also be increased b\ the same amount to 0.866 |»ig. or two limes the
original pressure.
II this process were repeated with a third cubic foot of water, the pressures
at the base of each cube would be 1.299 psig, 0.866 psig, and 0.133 psig,
respectively. It is evident that pressure varies wilh depth bclou a free water
surface. In general, each loot of elevation change, within a liquid, changes the
pressure by an amount equal to the weight-per-unit area of I fool of the liquid.
The rate of increase for water is 0.133 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. ( hie loot 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 leet ol head are equal to 43.3 psig.
Sec formal definition in the glossary of the appendix.
10
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0.433 PSIG
0.866 PSIG
FIGURE 2. Pressure exerted by 2 feet of water at sea level.
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.
14.7
PSIA
14.7
PSIA
14.7
PSIA
Sea Level
FIGURE 3. Pressure on the free surface of a liquid at sea level.
11
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If, as shown in figure 4, the tube is tightly capped and a vacuum pump is
used to evacuate all the air from the sealed tube, a vacuum with a pressure ol 0
psia is created within the tube. Because the pressure at any point in ;i static
fluid is dependent upon the height of that point above a reference line, such a>
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 ol v\aler
33.9 feet high and with the column open at the base, water would rise to lill
the column to a depth of 33.9 feet. In other words, the weight ol 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. Ill's is a partial vacuum with an
equivalent gage pressure of -5.0 psig.
i
;
33.9'
14.7
PSIA
\
r
(Cy"Zero" Absolute Pressure
IT
:
0.0
PSIA
! j
1
9.7
»SIA
.
4.7
»SIA
f
":"%,
:::::;^=Q3g)
or -14.7 Vacuum
Pump
or-5-0
PSIG
~f~
"j5 14.7 0.0
PSIA ° PSIG
w y Sea Level
FIGURE 4. Effect of evacuating air from a column.
12
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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
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.
Kigure 5 is a diagram of an inverted U-tube that has been filled with water
and placed in two open containers at sea level.
4.7 PSIA
10.3 PSIA
10.3 PSIA
FIGURE 5. Pressure relationships in a continuous fluid system at the
same elevation.
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.
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 still remain at 14.7 psia.
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 correspond-
ing level in the right tube above the free surface in the right container may also
be calculated.
13
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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 arrange-
ment will be recognized as a siphon. The crest of a siphon cannot be higher
than 33.9 feet above the upper liquid level, since the atmosphere cannot
support a column of water greater in height than 33.9 feet.
8.2 PSIA
'
1
14.7
PSIA
i^ __^_
f
5'
'
j
-^
5'
-/I
' 1
y
\
\
\
\
V-
\
. ,
-^
10.3 PSIA
4 14.7
10- PSIA
I1^
x ^\
\
J
•
J)
FIGURE 6. Pressure relationships in a continuous fluid system at
different elevations.
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 a
continuous fluid system.
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.
14
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Valve Open
Submerged Inlet r— I
FIGURE 7. Backsiphonage in a plumbing system.
FIGURE 8. Negative pressures created by constricted flow.
One of the common occurrences 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 by a further
reduction in 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 of the water in the line. Actually, in the illustration
shown, flow from the source of pollution would occur when pressure on the
suction side of the pump is less than pressure of the pollution source; but this
is backflow, which will be discussed below.
The preceding discussion has described some of the means by which negative
pressures may be created and which frequently occur to produce back-
siphonage. In addition to the negative pressure or reversed force necessary to
cause backsiphonage and backflow, there must also be the cross-connection or
15
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To
Fixture
Booster Pump
FIGURE 9. Dynamically reduced pipe pressures.
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. 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 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 backpressure.
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. Kven
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 difficult.
16
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Nonpotable Potable
FIGURE 10. Valved connection between potable water and nonpotablc fluid.
Condenser
f(
Sanitary Sewer
FIGURE ll. Valved connection between potable water and sanitary sewer.
The illustrations included in part B of the appendix are intended to describe
typical examples of baeksiphonage, showing in each case the nature of the link
or cross-connection, and the cause of the negative pressure.
Backflow
Backflow, as described in this manual, refers to reversed flow due to back-
pressure 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
See formal definition in the glossary of the appendix.
17
-------
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 centrifugal 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 connected.
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 back-
flow under pressure can occur, describing the cross-connection and the cause of
the reversed flow.
18
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Chapter 4. METHODS AND DEVICES FOR THE
PREVENTION OF BACKFLOW AND
BACKSIPHONAGE
The control of backflow and backsiphonage requires either the complete
removal of the cross-connection or the installation of a proper cross-connection
control device. Removal of the physical link is preferred because it eliminates
the possibility of failure of a mechanical device. However, the operation of
some fixtures, such as a siphon-jet water closet, requires a link in the form of a
submerged outlet. In this case, an acceptable cross-connection control device
should be employed to reduce the hazard significantly. There are no cases
where a cross-connection cannot be removed or corrected.
Airgap Separation
The only absolute means of eliminating the physical link is through the use
of the vertical airgap, as illustrated by figure 12. Airgaps should be used
wherever possible, and where used must not be bypassed.
Flood Level Rim
FIGURE 12. Airgap on lavatory.
19
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The supply inlet to the fixture should be terminated above the flood-level
rim of the fixture by a distance equal to at least two times the effective
opening1 of the fixture. Ideally, there should be no provision for extending the
fixture outlet below the flood-level rim. If the end of the supply pipe is
threaded or serrated to permit the connection of a hose, however, a properly
installed vacuum breaker should also be provided.
Some examples of generally used plumbing fixtures are shown in table 3.82
in chapter 7, subsection 3.82, page 39.
If an airgap separation is provided at each fixture, complete protection will
be provided within the building as well as to the municipal supply. The
separation may also be made at one point where the water service enters the
building. It must be remembered, however, that this protects only the
municipal water supply system and not the building system.
Surge Tanks
A surge tank, illustrated in figure 13, consists of a reservoir and pump
combination with the potable water supply to the reservoir delivered through
an airgap. The size of each unit is determined by the water demand rate which
it is to accommodate. The rate of flow into the receiving reservoir of the simple
surge tank shown in figure 13 is governed by the float valve. The booster pump
draws water from the reservoir, or surge tank, and discharges directly to the
distribution system under pressure. When the discharge of the booster pump is
to serve points where water will be withdrawn for domestic use, the surge tanks
should be covered properly to prevent contamination. The surge tank is often
used in installations where water is needed in industrial processes and may be
used to serve single fixtures, equipment units, or entire systems.
Butterfly
Valve
To Chemical Process
or other Nonpotable
Use Fixture
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
FIGURE 13. Surge tank and booster pump.
'See glossary in appendix.
20
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Color Coding
When two or more piping systems are used for water in a building or
industrial plant, extreme care should be taken not to interconnect the systems.
There may be a potable water system and systems carrying lesser quality water
such as for fire protection. To help prevent the possibility of the two systems
being interconnected, pipes should be identified adequately by legends and
color coding based on the American Standards Association Scheme for Identifi-
cation of Piping Systems (ASA A13.1-1956).
Color coding should not be used solely to identify the contents of pipes but
should b6 used supplementary to the use of legends. Potable water lines should
be painted green or with bands of green and the words "potable water"
stenciled on the pipe at appropriate intervals. Pipes carrying water for fire
protection should be painted red and be stenciled. Piping systems carrying
other material or water for other purposes should also be clearly identified
with the appropriate legends and color coding.
Booster Systems
Booster pumps are often required in high buildings. Frequently these booster
pumps are connected directly to the city water main or water service, under
which conditions there is always the possibility of creating a negative pressure
in the water main, as shown in figure 22 of appendix B. A simple surge tank
could be used to protect the city main in such cases. Its disadvantage is that all
or most of the city water pressure which otherwise might be available is lost
through the airgap. Also there is the hazard of introducing contamination
through the surge tank. A pressure limiting switch can be connected to the
booster pump suction to prevent the pump from creating negative pressures in
the main, but operators find it convenient to shunt around such a switch if
there is any interruption in service. Figure 14 illustrates a positive method of
negative pressure control, which at the same time permits the direct use of city
pressure when the pressure is adequate.
When the city pressure is sufficient, the booster pump is operated with full
city pressure applied to the intake side of the pump. An altitude, or pressure-
reducing valve, is installed below the reservoir to minimize the required
reservoir height. If the pressure in the water main drops below the pressure
differential of the pressure-reducing valve, air is drawn in through the pressure-
reducing valve, airbinding the pump and causing it to stop. If airbinding the
pump is undesirable, a low-water-level pump shutoff switch may be added to
the unit.
Vacuum Breakers
A fundamental factor in backsiphonage, as outlined in chapter 3, is vacuum
or negative pressure. If atmospheric pressure is admitted to a piping system
between a source of pollution and the origin of the vacuum, backsiphonage will
be prevented. This is the function of a vacuum breaker. It is not designed to
provide protection against backflow resulting from backpressure, and should
not be installed where backpressure may occur. Because a vacuum may be
created at numerous places in a piping system, a vacuum breaker must be
21
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Screened Vent
.——
Water Level
FIGURE14. Booster system.
located as near as possible to the fixture from which contamination is
anticipated. The position of a vacuum breaker must be sufficiently above the
fixture flood-level rim so that flooding or submergence of the vacuum breaker
or backpressure cannot occur.
A vacuum breaker may be installed either on the atmospheric side of a valve
or within a pressurized distribution system. A non-pressure-type vacuum
breaker is installed on the atmospheric side arid will operate or cycle each lime
the valve is used. This type should not be installed where it will remain under
pressure for long periods. A pressure-type vacuum breaker is installed in a
pressurized system and will operate only when a vacuum occurs The device is
usually spring loaded, and il should be specially designed to operale after
extended periods under pressure because corrosion and deposition of material
in the line might render it inoperable.
22
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Installation of a vacuum breaker on the atmospheric side of the last control
valve is always preferred and recommended because, by virtue of its position, it
prevents any contamination from being siphoned into the water system. A
vacuum breaker installed somewhere in the pressurized system does not
completely protect the system, and could, with certain piping arrangements,
allow backsiphonage into the water system. Vacuum breakers should be used in
a pressurized system only on specific authorization of the administrative
authority having jurisdiction.
The operation of one type of vacuum breaker is illustrated in figure 15. The
flow of water is downward and the disc is seated in the vertical position,
preventing water from spilling out the pipe (view 1). If a negative pressure
should develop in the supply line, atmospheric pressure would force the disc
into the horizontal position, thereby blocking the supply line, admitting air,
and preventing backsiphonage (views 2 and 3).
Vacuum
Disc
Atmospheric/
Pressure
N. Atmospheric
Pressure
Disc in Normal
Flow Position
Vacuum
Atmospheric
Pressure
Flow Just after
Vacuum is Applied
^Atmospheric
Pressure
Disc in Vacuum
Breaking Position
FIGURE 15. Operation of a vacuum breaker.
23
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Figure 16 shows a non-pressure-type vacuum breaker installation. The
serrated outlet laboratory sink supply might easily be extended by a hose to a
point below the flood-level rim of the laboratory sink, thus producing a cross-
connection. The vacuum breaker installation on the atmospheric side of the
control valve and between the cross-connection effectively protects the piping
system against backsiphonage.
Vacuum
Breaker
FIGURE 16. Typical non-pressure-type vacuum breaker installation.
Reduced Pressure Zone Backflow Preventer
In situations where it would be extremely difficult to provide a physical
break between two systems and where backpressures can be expected, a
reduced pressure zone backflow preventer (RPZ) can be used. This device
consists of two,hydraulically or mechanically loaded, pressure-reducing check
valves, with a pressure-regulated relief valve located between the two check
valves as shown by figure 17.
Flow from the left enters the central chamber against the pressure exerted by
the loaded check valve 1. The supply pressure is reduced thereupon by a
predetermined amount. The pressure in the central chamber is maintained
lower then 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
24
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Normal Direction of Flow
Reversed Direction of Flow
FIGURE 17. Reduced pressure zone backflow preventer
principle of operation.
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 atmosphere.
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
device.
Double Check Valve Assembly and Other Methods
Other methods and devices have been promoted for the separation ot
auxiliary systems or for the prevention of backflow. Among these are the single
check valve, and plain double check valve assembly, the double check valve-
double gate valve assembly, the swivel connection, and the barometric loop.
The single check valve offers no visual or mechanical means of determining
malfunctioning, and since all mechanical devices are subject to wear and
interference resulting from deposits and other factors, the single check valve is
not considered an adequate backflow preventer. Double check valve assemblies
25
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in series, including those with spacers and manual bleed valves, have similar
disadvantages. The advantage offered by the manual bleed valve is usually
negated by the human element which may cause the valve to remain closed.
The double check-double gate valve assembly, shown in figure 25 of
appendix B, is a very useful and, when properly maintained, reliable means of
backflow protection for intermediate degrees of hazard. This device has been in
service at some plants since the early 1900's. As in the case of other backflow
preventers, the double check-double gate valve assembly should be inspected at
regular intervals. Some health authorities have established programs of annual
inspection.
The double check-double gate system has the advantage of a low head loss.
With the gate valves wide open the two checks, when in open position, offer
little resistance to flow.
Double check-double gate assemblies should be well designed and con-
structed. The valves should be all bronze or, for larger sizes, galvanized gray
iron. The trim should be of bronze, or other corrosion-resistant material.
Springs should be bronze, stainless steel, or spring steel covered with a coat of
vinyl plastic. Valve discs should be of composition material with low water
absorption properties. Test cocks should be provided.
The swivel connection does not offer adequate protection against backflow
between the two systems that it interconnects. It should not be used to
connect a hazardous system to a potable system without the inclusion of an
acceptable means of backflow prevention.
The barometric loop consists of a vertical loop of pipe extending at least 35
feet above the highest fixture. The principle is that a complete vacuum cannot
raise water to an elevation greater than 33.9 feet. The device, however, does
not provide protection against backflow due to backpressure and the
installation of a pipe loop of this height is usually difficult and expensive. As a
result it is not widely used.
26
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Chapter 5. TESTING PROCEDURES FOR BACKFLOW
PREVENTERS
Vacuum Breakers
A vacuum breaker should be subjected to routine visual inspection to
determine that the device is functioning normally. Malfunction may be
indicated by excessive weeping or leakage of the device. Stains or watermarks
on the outside body of the device may also indicate malfunction.
Internal inspection should also be made periodically. Rubber membranes and
gaskets, valve seats, and the internal mechanism should be carefully inspected
for rupture, scoring of metal, scaling, corrosion, or any accumulation of dirt or
foreign matter that would prevent the safe operation of the device.
A complete inspection of a vacuum breaker installation also includes a
determination that the device has not been bypassed and that under no con-
ditions could it be subjected to backpressure. Vacuum breakers must be
installed above the flood-level rim of the equipment supplied and should be
located at the highest point in the part of the water system served so as to
preclude any possibility of backpressure being applied to the device. A
complete record, including date of installation and information on all
inspections, tests, and repairs, should be maintained on each device. Any
defects found during inspection or testing should be corrected immediately
before allowing the device to be placed back in service.
The basic concept in testing of a vacuum breaker for proper operation
involves a determination that the air inlet will open fully when there is little or
no water pressure inside the device. The canopy or hood on the vacuum
breaker should be removed, where possible, to expose the air inlet. When
testing a non-pressure-type vacuum breaker, the closest upstream valve should
be opened to allow water to fill the downstream piping. The valve is then
closed; the vent ports should open allowing air to enter the device and water to
flow out the downstream piping. If water does not continue to flow, or if there
is a mere trickle, the vacuum breaker is not opening properly. The defect
should be corrected immediately and the device retested.
When testing a pressure-type vacuum breaker, the system must first be
under pressure. (See fig. 18.) First valve 2 is closed, then valve 1. The test cock
should then be opened to lower the pressure and allow water to drain slowly
from the device. As the pressure in the device drops to near 0 psi, the air inlet
should open automatically if it is operating properly. If the air inlet remains
closed, the valve or spring may be corroded or fouled causing it to cement shut.
The defect should be corrected immediately by installing a new vacuum
breaker or by repairing the old one and retesting. Next, the system should be
repressurized by closing the test cock and opening valve 2 and then valve 1. As
the pressure increases, some water should discharge through the vent ports. If
the discharge continues as the system is repressurized, however, it means that
27
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Valve 2
Test Cock
Valve 1
FIGURE 18. Pressure-type vacuum breaker installation.
the valve has not seated properly and may be damaged or fouled. The defect
should be corrected immediately and the device completely retested.
Reduced Pressure Zone Backflow Preventer
In the operation of an RPZ, the reduced pressure zone between the two
check valves is maintained at a pressure less than the supply pressure by the
action of the pressure differential relief valve. The relief valve should be
capable of maintaining a reduced pressure zone, which is at least 2 psi less than
the supply pressure. If the supply pressure becomes less than 2 psi, the relief
valve opens and the pressure in the reduced pressure zone becomes
atmospheric. When field testing an RPZ, it should be observed that the device
has not been bypassed and that the relief valve can freely discharge water. The
device should undergo periodic internal inspection and should be cleaned or
repaired as necessary. Check valves and the pressure differential relief valve
should be checked for wear, corrosion, scaling, fouling, or other damage that
may cause malfunction.
Occasional discharge of water through the relief valve can be caused by
fluctuations in inlet pressure, and usually occurs when there is no flow through
the device. Continuous discharge of water through the relief valve under
flowing conditions indicates either that the relief valve is malfunctioning or
that check valve 1 is held in an open position. (See fig. 17.) Continuous
28
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discharge under no-flow conditions indicates that the differential relief valve is
malfunctioning, or that there is a leak in check valve l,or that a backflow
condition exists and check valve 2 is leaking.
Test Procedure
A field test of the device is used to determine if the pressure relief valve and
the two check valves are operating properly. A differential pressure gage with a
0-15-psi range and a working pressure of 500 psi and appropriate lengths of
hose with necessary fittings are needed for testing. (See fig. 19.)
Cheek Valve No. 1—) /Differential
/ Pressure
Gate Valve No. 1, | \ Re|ief Valve
A
Valve "A"
Valve "B
Check Valve No. 2
Gate Valve No. 2
Test Cock No. 4
Test Cock No. 3
Bypass Hose
Air Vents
Differential
Pressure Gage
Valve "C"
x Bypass Valve
FIGURE 19. Reduced pressure zone backflow preventer field test.
Step Number 1. Steps for testing check valve 1 for tightness against
backflow and measuring the pressure differential:
A. Open all test cocks individually to flush out any dirt and sediment and
then close.
B. Close gate valve 2 and open gate valve 1. If there is no drainage from the
relief valve, check valve 1 is closed tight.
C. Connect test hose between test cock 2 and valve B, and between test
cock 3 and valve C.
D. Close valve A and gage bypass valve.
E. Open test cocks 2 and 3.
F. Open valves B and C. Open air vents on gage to clear all air, then reclose.
29
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G. Open test cock 4 and allow it to drain slightly until gage reading stops
rising, then reclose and read differential gage pressure, which should be
above 5 psi.
Step Number 2. Steps for determining the differential pressure at which the
pressure differential relief valve will open:
A. With pressure holding constant above 5 psi, open very slowly the gage
bypass valve until pressure starts to drop slowly.
B. When the first drops of water discharge from the pressure relief valve,
pressure reading should not be below 2 psi.
C. Close bypass valve.X0pen test cock 4 and allow it to drain slightly until
gage reading stops rising. Then close test cock 4.
Step Number 3. Steps for testing check valve 2 for tightness against
backflow:
A. With pressure holding constant above 5 psi, connect hose from valve A
to test cock 4. Slowly open valve A and vent air from hose connection
at test cock 4. Tighten connection and open test cock 4.
B. Differential pressure reading should not drop below 5 psi.
Double Check-Double Gate Valves
The double check-double gate valve assembly should include test cocks as
shown in figure 20. A method for testing the check valves is as follows:
Gate A
Gate G
Public
Supply
Test Cocks
Private
Supply
FIGURE 20. Method of testing check valves.
A. Where Backpressure Is Available on Private Supply.
1. Open all test cocks individually to flush out any sediment or scale.
2. Close gate valves A and G.
3. Open test cocks B and F, successively. If leakage occurs, gate valve(s) A
and/or G are leaking and must be repaired before continuing test.
4. a. Open gate valve G and test cock D. If leakage does not cease, check
valve E is leaking and must be repaired. If leakage ceases, check valve
E is tight.
b. Temporarily connect a hose between test cocks D and F and open
30
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both. Open test cock B. If leakage does not cease, check valve C is
leaking and must be repaired. If leakage ceases, check valve C is tight.
c. If check valves are repaired, repeat the test as above.
5. When the test is complete, close test cocks and remove the hose. Leave
gate valves A and G in their proper position.
B. Where Insufficient Backpressure Is Available on Private Supply.
1. Open all test cocks individually to flush out any sediment or scale.
2. Close gate valves A and G.
3. Open test cocks B and F, successively. If leakage occurs, gate valve(s) A
and/or G are leaking and must be repaired before continuing test.
4. a. Temporarily connect a hose between test cocks J and F and open
both. Open test cock D. If leakage does not cease, check valve E is
leaking and must be repaired. If leakage ceases, check valve E is tight.
6. Close cocks J and F. Temporarily connect the hose between test
cocks J and D and open both. Open test cock B. If leakage does not
cease, check valve C is leaking and must be repaired. If no leakage
occurs, check valve C is tight.
c. If check valves are repaired, repeat the test as above.
5. When the test is complete, close test cocks and remove the hose. Leave
gate valves A and G in their proper position.
31
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Chapter 6. ADMINISTRATION OF A CROSS-
CONNECTION CONTROL PROGRAM
Responsibility
Public health personnel, waterworks officials, plumbing inspectors, building
managers, plumbing installers, and maintenance men all share to some degree
the responsibility for protecting the health and safety of individuals and the
public from contaminated water. These responsibilities include insuring
sanitary design and installation practices in piping systems and the supervision
of the installation and maintenance of these systems. Public health officials
should promote the development of sanitary design of plumbing systems and
encourage as well as assist in the training of persons responsible for their
installation and maintenance. Officials responsible for the inspection of
plumbing installations should require the maximum protection against
backflow that is consistent with good judgment and the public safety.
Plumbing installers and maintenance personnel should observe and avoid or
eliminate possibilities for backflow and be diligent in adherence to plumbing
codes and ordinances.
Where plumbing defects are detected, notification of the persons having
authority for the correction of such defects should be made in writing, and the
responsible person should cause these defects to be corrected as soon as
possible.
Public Water Supply Protection
Waterworks officials should survey their own and their customers'
distribution systems for cross-connections on a continuing basis and should
provide a satisfactory program for the elimination of health hazards.
Frequently, their responsibility ends at the property line but in some
municipalities it extends to the building piping. Waterworks officials often
prescribe the installation of a backflow prevention device in the service line to
a premise where hazardous use of water is found. The requirement of an airgap
in the service line to a premise where extreme hazard is possible may be
warranted. Reduced pressure principle or double check-double gate backflow
preventers are often used in cases of lesser hazard.
Direct connections between potable and nonpotable water supply systems
should be eliminated or properly protected, and interconnections with other
public water supply systems should be permitted only with the approval of
health authorities. Private wells should have no connection to the potable,
public water supply system.
The potable water distribution system should be so designed that the sizes of
pipes are adequate to supply water in the amounts and at the pressures needed.
32
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When a system is sized to meet the needs of peak fire demand, other uses are
usually covered, but at the time of large fires water pressure in remote parts of
the system may be reduced even to the point of vacuum. Following a large fire,
water and health authorities should be alert for appearances of contamination.
When there are main breaks due to deterioration or damage, such as by
flood, large quantities of water escape at the affected point and pressures
elsewhere in the system may drop seriously. Breaks should be repaired
promptly and an alert maintained for the appearance of contamination. The
precaution of first thoroughly flushing, then disinfecting repaired and new pipe
sections should be observed.
Priority of Action
Plumbing defects are in existence and defects are constantly being created in
new plumbing systems and in altering existing systems. The elimination of
these health hazards will be possible only through a well-planned and
continuing program of instruction, plumbing surveillance, and repaid. Many
types of cross-connections exist, and the danger to public health resulting from
each differs widely. The possibility of causing serious pollution of the potable
water supply system is dependent upon the degree of hazard of the
contaminant and the probability of reversed flow.
Although, statistically, the probability of reversed flow may seem remote,
reliance should not be placed upon this factor. Complete removal of all cross-
connections should be undertaken in an organized manner and a priority
system based upon the degree of hazard involved should be established. It is
not feasible in this manual to assign priority to all types of cross-connections,
or even to classify them, except in a general way. Determining priority of
action in their removal should be based primarily on the nature of the
pollutant. High priority should be given any cross-connection between a
potable water supply and a piping system or reservoir conveying or containing
sewage, toxic or hazardous chemicals, or nonpotable water. All such
connections should be broken immediately and properly protected.
Obsolete fixtures, such as tubs and lavatories having inlets terminating below
the overflow level, have a lower priority but outlets should be raised or the
fixtures replaced. Fixtures which have serrated or threaded inlets that would
permit the extension of these inlets below the flood level rim could be
particularly hazardous and should be provided with vacuum breakers. Where
this is not possible, the fixtures should be replaced on a systematic, improve-
ment basis. Fixtures that can siphon only a small amount of relatively low-
hazard waste water do not warrant urgent or drastic action and can be given a
lower priority. These illustrations describe the common extremes of urgency or
priority, and only a careful evaluation of the circumstances surrounding each
specific plumbing hazard will enable establishing reasonable priority for
intermediate situations. As stated previously, in establishing a priority of
action, reliance should not be placed upon the probability factor of the
occurrence of reversed flow.
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Method of Action
A broad program of cross-connection control should include instruction,
inspection, improvements, and enforcement. Control on new installations
should be accomplished through plan review and installation inspection.
Control and elimination of existing hazards should be accomplished through
routine inspection and periodic surveys at definite intervals. Trained personnel,
competent in plan examination and hazard evaluation, should supervise the
control program. Sanitary inspectors who have qualifications equivalent to
licensed plumbers and who have been specially trained in cross-connection
control should be assigned to the task of inspecting new and existing plumbing
installations. The results of periodic surveys should be tabulated and
summarized for comparison with the results of previous surveys. Only through
this means will improvement, or lack of improvement, be noted. Through a
summarization of the number of violations of specific types, effective action
may be directed against the most prevalent and most hazardous violations.
As an aid to the less-experienced inspector, a limited tabulation of typical
hazardous connections is listed in the appendix of this manual along with
several illustrations of backsiphonage and backflow. Also shown in the
appendix is a survey form for reporting on inspections for health hazards.
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Chapter 7. CROSS-CONNECTION CONTROL
ORDINANCE PROVISIONS
INTRODUCTION
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 parts.
1. Authority for establishment of a program.
2. The technical provisions relating to eliminating backflow and cross-
connections.
3. Penalty provisions for violations.
The following simple form is suggested for municipalities who desire to adopt a
cross-connection control ordinance. The technical provisions are for the most
part excerpted from a revision of the National Plumbing Code prepared by the
Public Health Service Technical Committee on Plumbing Standards (1962).
Where the National Plumbing Code, or subsequent revisions thereof, is in
effect, the technical sections of the following can be replaced by a statement of
reference to the Code. Communities adopting ordinances should check with
State health officials to assure conforrhance with State codes. The form of the
ordinance should comply with local legal requirements.
ORDINANCE FOR THE CONTROL OF BACKFLOW
AND CROSS-CONNECTIONS
Section 1. Authority
1.1 Responsibility of the Director. The Director, Department
of. , or his designated agent, shall inspect the plumbing in
every building or premises in this City as frequently as in his judgment may be
necessary to ensure that such plumbing has been installed in such a manner as
to prevent the possibility of pollution of the water supply of the city by the
plumbing. The director shall notify or cause to be notified in writing the owner
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or authorized agent of the owner of any such building or premises, to correct,
within a reasonable time set by the Director, any plumbing installed or existing
contrary to or in violation of this ordinance, and which in his judgment, may,
therefore, permit the pollution of the city water supply, or otherwise adversely
affect the public health.
1.2 Inspection. The Director, or his designated agent, shall have the right
of entry into any building, during reasonable hours, for the purpose of making
inspection of the plumbing systems installed in such building or premises pro-
vided that with respect to the inspection of any single family dwelling, consent
to such inspection shall first be obtained from a person of suitable age and
discretion therein or in control thereof.
Section 2. Definitions
2.1 Agency. The department of the municipal government invested with
, the authority and responsibility for the enactment and enforcement of this
ordinance.
2.2 Airgap. The unobstructed vertical distance through the free atmos-
phere 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 recep-
tacle.
2.3 Approved. Accepted by the agency as meeting an applicable specifi-
cation stated or cited in this ordinance, or as suitable for the proposed use.
2.4 Auxiliary Supply. Any water source or system other than the potable
water supply that may be available in the building or premises.
2.5 Back/low. 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.
2.6 Backflow Preventer. A device or means to prevent backflow.
2.7 Backsiphonage. Backflow resulting from negative pressures in the
distributing pipes of a potable water supply.
2.8 Barometric Loop. A loop of pipe rising at least 35 feet, at i(ts topmost
point, above the highest fixture it supplies.
2.9 Check Valve. A self-closing device which is designed to permit the
flow of fluids in one direction and to close if there is a reversal of flow.
2.10 Contamination. See Pollution.
2.11 Cross-Connection. Any physical connection between a potable water
supply and any waste pipe, soil pipe, sewer, drain, or any unapproved source or
system. Furthermore, it is any potable water supply outlet which is submerged
or can be submerged in waste water and/or any other source of contamination.
See Backflow and Backsiphonage.
2.12 Drain. Any pipe that carries waste water or waterborne wastes in a
building drainage system.
2.13 Fixture, Plumbing. Installed receptacles, devices, or appliances
supplied with water or that receive or discharge liquids or liquid-borne wastes
2.14 Flood-Level Rim. The edge of the receptacle from which water over-
flows.
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2.15 Hazard, Health. Any conditions, devices, or practices in the water
supply system and its operation which create, or, in the judgment of the
Director, may create, a danger to the health and well-being of the water con-
sumer. An example of a health hazard is a structural defect in the water supply
system, whether of location, design, or construction, that regularly or occa-
sionally may prevent satisfactory purification of the water supply or cause it to
be polluted from extraneous sources.
2.16 Hazard, Plumbing. Any arrangement of plumbing including piping
and fixtures whereby a cross-connection is created.
2.17 Hydro pneumatic Tank. A pressure vessel in which air pressure acts
upon the surface of the water contained within the vessel, pressurizing the
water distribution piping connected to the vessel.
2.18 Inlet. The open end of the water supply pipe through which the
water is discharged into the plumbing fixture.
2.19 Plumbing System. Includes the water supply and distribution pipes,
plumbing fixtures, and traps; soil, waste, and vent pipes; building drains and
building sewers including their respective connections, devices, and appurte-
nances within'the property lines of the premises; and water-treating or water-
using equipment.
2.20 Pollution. The presence of any foreign substance (organic, inorganic,
radiological, or biological) in water that tends to degrade its quality so as to
constitute a hazard or impair the usefulness of the water.
2.21 Reduced Pressure Principle Back/low Preventer. An assembly of dif-
ferential valves and check valves including an automatically opened spillage
port to the atmosphere designed to prevent backflow.
2.22 Surge Tank. The receiving, nonpressure vessel forming part of the
airgap separation between a potable and an auxiliary supply.
2.23 Vacuum. Any pressure less than that exerted by the atmosphere.
2.24 Vacuum Breaker, Nonpressure Type. A vacuum breaker designed so
as not to be subjected to static line pressure.
2.25 Vacuum Breaker, Pressure Type. A vacuum breaker designed to
operate under conditions of static line pressure.
2.26 Water, Potable. Water free from impurities in amounts sufficient to
cause disease or harmful physiological effects. Its bacteriological and chemical
quality shall conform to the requirements of the Federal Drinking Water
Standards or to Ihe regulations of the public health authority having
jurisdiction.
2.27 Water, Nonpotable. Water that is not safe for human consumption
or that is of questionable potability.
Section 3. General (Technical) Requirements
3.1 General. A potable water supply system shall be designed, installed,
and maintained in such manner as to prevent contamination from nonpotable
liquids, solids, or gases from being introduced into the potable water supply
through cross-connections or any other piping connections to the sytem.
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3.2 Cross-Connections Prohibited. Cross-connections between potable
water systems and other systems or equipment containing water or other sub-
stances of unknown or questionable safety are prohibited except when and
where, as approved by the authority having jurisdiction, suitable protective
devices such as the reduced pressure zone backflow preventer or equal are
installed, tested, and maintained to insure proper operation on a continuing
basis.
3.3 Interconnections. Interconnection between two or more public water
supplies shall be permitted only with the approval of the health authority
having jurisdiction.
3.4 Individual Water Supplies. Cross-connections between an individual
water supply and a potable public supply shall not be made unless specifically
approved by the health authority having jurisdiction.
3.5 Connections to Boilers. Potable water connections to boilers shall be
made through an airgap or provided with an approved backflow preventer.
3.6 Prohibited Connections to Fixtures and Equipment. Connection to the
potable water supply system for the following is prohibited unless protected
against backflow in accordance with section 3.8 or as set out herein.
(a) Bidets.
(b) Operating, dissection, embalming, and mortuary tables or similar
equipment: in such installation the hose used for water supply shall terminate
at least 12 inches away from every point of the table or attachments.
(c) Pumps for nonpotable water, chemicals, or other substances: priming
connections may be made only through an airgap.
(d) Building drainage, sewer, or vent systems.
(e) Any other fixture of similar hazard.
3.7 Refrigerating Unit Condensers and Cooling Jackets. Except where pot-
able water provided for a refrigerator condenser or cooling jacket is entirely
outside the piping or tank containing a toxic refrigerant, the inlet connection
shall be provided with an approved check valve. Also adjacent to and at the
outlet side of the check valve, an approved pressure relief valve set to relieve at
5 psi above the maximum water pressure at the point of installation shall be
provided if the refrigeration units contain more than 20 pounds of refrigerants.
3.8 Protection Against Backflow and Backsiphonage.
3.81 Water Outlets. A potable water system shall be protected against
backflow and backsiphonage by providing and maintaining at each outlet:
(a) Airgap. An airgap, as specified in section 3.82, between the potable
water outlet and the flood level rim of the fixture it supplies or between the
outlet and any other source of contamination, or
(b) Backflow Preventer. A device or means to prevent backflow.
3.82 Minimum Required Airgap.
(a) How Measured. The minimum required airgap shall be measured ver-
tically from the lowest end of a potable water outlet to the flood rim or line of
the fixture or receptacle into which it discharges.
(b) Size. The minimum required airgap shall be twice the effective
opening of a potable water outlet unless the outlet is a distance less than three
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times the effective opening away from a wall or similar vertical surface, in
which cases the minimum required airgap shall be three times the effective
opening of the outlet. In no case shall the minimum required airgap be less
than shown in table 3.82.
TABLE 3.82.—Minimum airgaps for generally used plumbing fixtures
Fixture
Lavatories and other fixtures with effective openings
not greater than Vi-in. diameter
Sink, laundry trays, goose-neck bath faucets and other
fixtures with effective openings not greater than %-in.
diameter
Over rim bath fillers and other fixtures with effective
openings not greater than 1-in. diameter
Drinking water fountains— single orifice 7/16 (0.437) in.
diameter or multiple orifices having total area of
0.150 sq. in. (area of circle 7/16-in. diameter) ....
Effective openings greater than 1 inch
Minimum
When not
affected by
near walli
(inches)
1.0
1.5
2.0
1.0
(3)
airgap
When
affected by
near wall2
(inches)
1.50
2.25
3.0
1.50
(4)
1 Side walls, ribs, or similar obstructions do not affect airgaps when spaced from inside
edge of spout opening a distance greater than 3 times the diameter of the effective opening
for a single wall, or a distance greater than 4 times the diameter of the effective opening
for 2 intersecting walls.
2 Vertical walls, ribs, or similar obstructions extending from the water surface to or
above the horizontal plane of the spout opening require a greater airgap when spaced
closer to the nearest inside edge of spout opening than specified in note 1 above. The
effect of 3 or more such vertical walls or ribs has not been determined. In such cases, the
airgap shall be measured from the top of the wall.
3 2 times diameter of effective opening.
4 3 times diameter of effective opening.
3.83 Approval of Devices. Before any device for the prevention of
backflow or backsiphonage is installed, it shall have first been certified by a
recognized testing laboratory acceptable to the agency Director. Devices
installed in a building potable water supply distribution system for protection
against backflow shall be maintained in good working condition by the person
or persons responsible for the maintenance of the system.
The agency Director or his designee shall inspect routinely such devices and
if found to be defective or inoperative shall require the replacement thereof.
3.84 Installation of Devices.
(a) Vacuum Breakers. Vacuum breakers shall be installed with the
critical level at least 6 inches above the flood level rim of the fixture they serve
and on the discharge side of the last control valve to the fixture. No shutoff
valve or faucet shall be installed beyond the vacuum breaker. For closed equip-
ment or vessels such as pressure sterilizers the top of the vessel shall be treated
as the flood level rim but a check valve shall be installed on the discharge side
of the vacuum breaker.
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(b) Reduced Pressure Principle Back/low Preventer. A reduced pressure
principle type backflow preventer may be installed subject to full static pres-
sure.
(c) Devices of All Types. Backflow and backsiphonage preventing
devices shall be accessibly located preferably in the same room with the fixture
they serve. Installation in utility or service spaces, provided they are readily
accessible, is also permitted.
3.85 Tanks and Vats-Below Rim. Supply.
(a) Where a potable water outlet terminates below the rim of a tank or
vat and the tank or vat has an overflow of diameter not less than given in table
3.85, the overflow pipe shall be provided with an airgap as close to the tank as
possible.
TABLE 3.85.—Sizes of overflow pipes for water supply tanks
Maximum capacity of water
supply line to tank
0— SOgpm
50-150 gpm
100-200 gpm
200-400 gpm
Diameter of
overflow
pipe (inches
ID)
2
2'/2
3
4
Maximum capacity of water
supply line to tank
400—700 gpm
700—1 000 gpm
Over 1,000 gpm
Diameter of
overflow
pipe (inches
ID)
5
5
3
(b) The potable water outlet to the tank or vat shall terminate a distance
not less than 1/2 times the height to which water can rise in the tank above the
top of the overflow. This level shall be established at the maximum flow rate of
the supply to the tank or vat and with all outlets except the airgap overflow
outlet closed.
(c) The distance from the outlet to the high water level shall be measured
from the critical point of the potable water supply outlet.
3.86 Protective Devices Required. Approved devices to protect against
backflow and backsiphonage shall be installed at all fixtures and equipment
where backflow and/or backsiphonage may occur and where a minimum airgap
cannot be provided between the water outlet to the fixture or equipment and
its flood-level rim.
(a) Connections Not Subject to Backpressure. Where a water connection is
not subject to backpressure, a vacuum breaker shall be installed on the dis-
charge side of the last valve on the line serving the fixture or equipment. A list
of some conditions requiring protective devices of this kind is given in table
3.86A, "Cross-Connections Where Protective Devices are Required and Critical
Level (C-L) Settings for Vacuum Breakers."
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TABLE 3.86A.—Cross-connections where protective devices are required and critical
level (C—L) settings for vacuum breakers "
Fixture or equipment
Method of installation
Aspirators and ejectors
Dental units .
Dishwashing machines . . .
Flushometers ( closet & urinal)
Garbage can cleaning machine
Hose outlets
Laundry machines ...
Lawn sprinklers
Steam tables
Tank and vats
Trough urinals
Flush tanks
Hose bibbs (where aspirators or
ejectors could be connected).
C—L at least 6 in. above flood level of receptacle
served.
On models without built-in vacuum breakers—
C—L at least 6 in. above flood level rim of bowl.
C—L at least 6 in. above flood level of machine.
Install on both hot and cold water supply line.
C—L at least 6 in. above top of fixture supplies.
C—L at least 6 in. above flood level of machine.
Install on both hot and cold water supply lines.
C—L at least 6 in. above highest point on hose line.
C—L at least 6 in. above flood level of machine.
Install on both hot and cold water supply lines.
C—L at least 12 in. above highest sprinkler or dis-
charge outlet.
C—L at least 6 in. above flood level.
C—L at least 6 in. above flood level rim or line.
C—L at least 30 in. above perforated flush pipe.
Equip with approved ball cock. Where ball cocks
touch tank water equip with vacuum breaker at
least 1 in. above overflow outlets. Where ball
cock does not touch tank water install ball cock
outlet at least 1 in. above overflow outlet or pro-
vide vacuum breaker as specified above.
C—L at least 6 in. above flood level of receptacle
served.
"Critical level (C-L) is defined as the level to which the vacuum breaker may be sub-
merged before backflow will occur. Where the C-L is not shown on the preventer, the
bottom of the device shall be taken as the C-L.
(b) Connections Subject to Backpressure. Where a potable water con-
nection is made to a line, fixture, tank, vat, pump, or other equipment with a
hazard of backflow or backsiphonage where the water connection is subject to
backpressure, and an airgap cannot be installed, the Director may require the
use of an approved reduced pressure principle backflow preventer. A partial list
of such connections is shown in table 3.86B.
TABLE 3.86B.—Partial list of cross-connections which may be subject to backpressure
Chemical lines
Dock water outlets
Individual water supplies
Industrial process water lines
Pressure tanks
Pumps
Steam lines
Swimming pools
Tank and vats—bottom inlets
Hose bibbs
3.87 Barometric Loop. Water connections where an actual or potential
backsiphonage hazard exists may in lieu of devices specified in section 3.86 be
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provided with a barometric loop. Barometric loops shall precede the point of
connection.
3.88 Double Check-Double Gate Valves. The Director may authorize in-
stallation of approved, double check-double gate valve assemblies with test
cocks as protective devices against backflow in connections between a potable
water system and other fluid systems which present no significant health
hazard in the judgment of the Director.
3.89 Low Pressure Cutoff Required on Booster Pumps. When a booster
pump is used on a water pressure booster system and the possibility exists that
a positive pressure of 10 psi or less may occur on the suction side of the pump,
there shall be installed a low-pressure cutoff on the booster pump to prevent
the creation of a vacuum or negative pressure on the suction side of the pump,
thus cutting off water to other outlets.
Section 4. Maintenance Requirements
4.1 General Requirements. It shall be the responsibility of building and
premise owners to maintain all backflow preventers and vacuum breakers with-
in the building or on the premises in good working order and to make no
piping or other arrangements for the purpose of bypassing backflow devices.
4.2 Backflow Preventers. Periodic testing and inspection schedules shall be
established by the Director for all backflow preventers and the interval
between such testing and inspections and overhauls of each device shall be
established in accordance with the age and condition of the device. Inspection
intervals should not exceed 1 year, and overhaul intervals should not exceed 5
years. These devices should be inspected frequently after the initial installation
to assure that they have been installed properly and that debris resulting from
the installation has not interfered with the functioning of the device. The
testing procedures shall be in accordance with the manufacturer's instructions
when approved by the Director.
Section 5. Violations and Penalties
5.1 Notification of Violation. The Director shall notify the owner, or
authorized agent of the owner, of the building or premises in which there is
found a violation of this ordinance, of such violation. The Director shall set a
reasonable time for the owner to have the violation removed or corrected.
Upon failure of the owner to have the defect corrected by the end of the
specified time interval the Director may, if in his judgment an imminent health
hazard exists, cause the water service to the building or premises to be termi-
nated, and/or recommend such additional fines or penalties to be invoked as
herein may be provided.
5.2 Fines. The owner or authorized agent of the owner responsible for the
maintenance of the plumbing systems in the building who knowingly permits a
violation to remain uncorrected after the expiration of time set by the Director
shall, upon conviction thereof by the court, be required to pay a fine of not
more than $100 for each vioktion. Each day of failure to comply with the
requirements of the ordinance, after the specified time provided under 5.1
shall constitute a separate violation.
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APPENDIX A-PARTIAL LIST OF PLUMBING HAZARDS
Fixtures With Direct Connections
Description
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
Chlorinator
Coffee urn
Cooling system
Dishwasher
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 Inlets
Description
Baptismal fount
Bathtub
Bedpan washer, flushing rim
Bidet
Brine tank
Cooling tower
Cuspidor
Drinking fountain
Floor drain, flushing rim
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Garbage can washer
Ice maker
Laboratory sink, serrated nozzle
Laundry machine
Lavatory
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
APPENDIX B-ILLUSTRATIONS OF BACKSIPHONAGE
The following pages illustrate typical plumbing installations where back-
siphonage is possible.
FIGURE 21. Backsiphonage-case 1.
Backsiphonage — Case 1 (fig. 21)
A. Contact Point: A rubber hose is submerged in a bedpan wash sink.
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H. lama's of Rewwil l'km<: ( I) A sterilizer connected to Ihe water supply is allowed to
cool without opciiiic; the air vent. As it mols. 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 pres-
sure at the water closets to atmospheric producing a reversal of Ihe flow.
(.. Suggi'stvil i.«rre<-;iofi: The waler connection at Ihe hedpan wash sink and I he .sterilizer
should he provided with properly installed hackflow preventers.
nun
nnnnnn
nnnnnn
onnnnn
Ku;ilKK 22. Backriphonage—case 2.
Backsiphonage—Case 2 (fig. 22)
A. I'anlact I'oint: A rubber hose Ls submerged in a laboratory sink.
B. Caute of Reversed ik>ir: Two opposite multistory buildings are connected to Ihe same
waler main, which often lacks adequate pressure. The building on Ihe right has installed
a booster pump. When the pressure is inadequate in the main, Ihe building booster
pump starts pumping, producing a negative pressure in Ihe main and causing a reversal
of flow in the opposite building.
(!. SuKgcsli'tl (.orri'rlion: The laboratory sink waler outlet should be provided with a
vacuum breaker. The water service line lo the booster pump should be equipped with a
device to cut off the pump when pressure approaches a negative head or vacuum.
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FIGURE 23. Backsiphonage-case 3.
Backsiphonage—Case 3 (fig. 23)
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 4 (fig. 24)
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 dinrtly
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 flow.
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.
Backsiphonage—Case 5 (fig. 25)
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 in-
stalled in the line to the gasoline storage tank or a surge tank and pump should be
provided in mat line.
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Main
r n d
n n [
n n n
~\ n n
n
FIGURE 24. Backsiphonage-case 4.
FIGURE 25. Backsiphonage—case 5.
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FIGURE 26. Backsiphonage-case 6.
Backsiphonage— Case 6 (fig. 26)
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 bathtub.
C. Suggested Correction: The hot and cold water inlets to the bathtub should be above the
rim of the tub.
APPENDIX C-ILLUSTRATIONS OF BACKFLOW
The following pages present illustrations of typical plumbing installations where back-
flow resulting from backpressure is possible.
FIGURE 27. Backflow case 1.
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Backflow-Case 1 (fig. 27)
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 control.
B. Cause of Reversed How: The boiler water recirculation pump discharge 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 valve.
C. Suggested Correction: As minimum protection two check valves in series should be
provided in the makeup watcrline to the boiler system. An airgap separation or reduced
pressure principle backflow preventer is better.
FIGURE 28. Baokflow-case 2.
Backflow-Case 2 (fig. 28)
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 How: 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
broken.
Backflow-Case 3 (fig. 29)
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 municipal supply.
t 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.
49
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City Main
•••
To Potable System,
FIGURE 29. Backflow-case 3.
Backflow-Case 4 (fig. 30)
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.
ACME WOOLEN MILLS |
J
j A
F,A^
Sprinkler System
i
I
M
I
FIGURE 30. Backflow case 4.
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APPENDIX D-ILLUSTRATIONS OF AIRGAPS
The following illustrations describe methods of providing an airgap discharge to a waste
line which may be occasionally or continuously subject to backpressure.
Force Main
FlGl'RE 31. Airgap to sewer subject to backpressure—force main.
2XD
Indirect Waste
Ball-Check
Support Vanes
Horizontal Waste
Gravity Drain
FIGURE 32. Airgap to sewer subject to backpressure—gravity drain.
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Nonpotable Supply
Potable Supply
FIGURE 33. Fire system makeup tank for a dual water system.
APPENDIX E-ILLUSTRATIONS OF VACUUM BREAKERS
Vacuum Closes Gate
Air Enters
Here Pre-
venting Rise
of Contamin
ated Liquids
in Fixtures
Flush
Connection
Cowl Nut
Air Vent
B
FIGURE 34. Vacuum breakers.
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NOTE:
(T)'/2" or %" Gate Valve
(Y)'/2" or %" Sch. 40. Galv.
(3)'/2" or %" Vacuum Breaker
(T)'/2" %" EM. M. I. Galv.
MHExterior Building Wall
(T)l" Sleeve, Sch. 40
(7J Handwheel
MMlPS Hose Adapter
MnCoupling M. I. Galv.
(ToV/2" °f %" Nipple
Plan
Section "A""A"
FIGURE 35. Vacuum breaker arrangement for an outside hose hydrant.
(By permission of Mr. Gustave J. Angele ST., P.E. Formerly Plant Sanitary
Engineer, Union Carbide Nuclear Division, Oak Ridge, Tenn.)
APPENDIX F-GLOSSARY
Air gap
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 receptacle.
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.
Backflow Connection
Any arrangement whereby backflow can occur.
Backflow Preventer
A device or means to prevent backflow.
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Backflow Preventer, Reduced Pressure Principle Type
An assembly of differential valves and check valves including an automatically opened
spillage port to the atmosphere.
Backsiphonage
Backflow resulting from negative pressures in the distributing pipes of a potable water
supply.
Cross- Connection
Any physical connection or arrangement between two otherwise separate piping
systems, one of which contains potable water, and the other, water of unknown or
questionable safety, or steam, gases, or chemicals, whereby there may be a flow from one
system to the other. No physical cross-connection should be permitted between public or
private water distribution systems containing potable water and any other system
containing water of questionable quality or containing contaminating or polluting
substances.
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 of equivalent cross-sectional area.
Flood-Level Rim
The edge of the receptacle from which water overflows.
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 pressure.
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 require-
ments of the Public Health Service Drinking Water Standards or the regulation of the
public health authority having jurisdiction.
Vacuum
Any absolute pressure less than that exerted by the atmosphere.
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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.
APPENDIX G-BIBLIOGRAPHY
A 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.
Accepted Procedure and Practice in Cross-Connection Control, Pacific Northwest Section,
American Water Works Association, Oct. 1971.
Angele, Gustave J., Cross-Connection and Back/low Prevention, American Water Works
Association. Supplementary Reading Library Series - No. S106, New York 10016.
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. II, No. 9, Dec. 1953, D.C.
Dept. of Public Health, Washington, D.C.
Dawson, F. M., and Kalinske, A. A., Report on Cross-Connections and Backsiphonage
Research, Technical Bulletin No. 1, National Association of Plumbing, Heating, Cooling
Contractors, Washington, D.C.
How To Prevent Industrial Cross-Connection Dangers, Water Works Engineering, Feb.
1962.
Manual of Cross-Connection Control, Foundation for Cross-Connection Control Research,
University of Southern California, Los Angeles, Calif. 90007, Mar. 1969.
Regulations Relating To Cross-Connections, except from the California Administrative
Code, Title 17, Public Health, 1956.
Springer, E. K., and Reynolds, K. C., Definitions and Specifications of Double Check
Valve Assemblies and Reduced Pressure Principle Backflow Prevention Devices,
University of Southern California, School of Engineering Rept. 48-101, Jan. 30,1959.
Taylor, F. B., and Skodje, M. T., Cross-Connections, A Hazard in All Buildings, Modern
Sanitation and Building Maintenance, Vol. 14, No. 8, Aug. 1962.
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. 1,
Sept. 1970; Pt. 2, Oct. 1970.
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APPENDIX H
CROSS-CONNECTION SURVEY FORM
Place: Date:.
Location: Investigator(s):.
Building Representative(s) and Title(s):
WaterSource(s):-
Piping System(s):-
Points of Interconnection:
Special Equipment Supplied with Water & Source:
Remarks or Recommendations:.
NOTE: Attach sketches of cross-connections found where necessary for clarity of
description. Attach additional sheets for room by room survey under headings
Room Number _ Description of
Cross-Connectio n(s)
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INDEX
Page
Administrative Authority 23, 35
Airgap 19, 20, 21, 32
Auxiliary Piping 16
Auxiliary System 18, 25
Backflow 9, 15, 1749, 21, 25, 26
29, 32, 34
Backflow Preventers
Barometric Loop 25,26
Double Check Valve 25
Double Check-Double
Gate Valve 25, 26, 32
Reduced Pressure
/one Device 24, 25, 32
Single Check Valve 25
Swivel Connection 25, 26
Tests 27-30
Vacuum Breaker-Non-
Pressure Type 22, 24
Vacuum Breaker-
Pressure Type 22
Backpressure 16, 18, 21, 22, 24-27
30,31
Backsiphonage 9, 15-17, 19, 21, 23
24,34
25, 26
, 20, 21
Barometric Loop
Booster Pump 15, 18, .'
Check Valves 25, 26, 32
Codes and Ordinances 32, 35-42
Connections — Basic Types
Solid Pipe 16
Submerged Inlet-Outlet 16, 19
Valved 17
Control Program 32-34
Color Coding 21
Chemical Poisonings
Arsenic 4, 6
Chromatcs 5, 7
Chlorides 5
Ethylene C.lycol 6
Fertilizer 8
Cross-Conncction
Causes 1
Definition 1, 9, 54
Examples 3-8, 44-50
Ordinances 35-42
Policy, AWWA vii
Prevention 1,2
Survey Form 56
Effective Opening 20
Flood Level Rim 16, 20, 22, 24, 27
33
Inspection and Maintenance 18
Interconnections 21, 32
Pressure
Absolute 9, 12
Atmosphere 9,11, 21, 23, 25, 28
Differential 18, 21, 25, 28-30
Gage 9, 12
Negative 17,21,23
Static 12-14
Water 10, 16, 21, 27
Pressure Head 10
Pressure-Reducing Valve 21
Private Wells 32
Pump Air Binding 21
Reduced Pressure /one
Backflow Preventer 24, 25, 32
Siphon Theory 11-17
Surge Tank 20, 21
Swivel Connection 25, 26
Tests - Backflow Preventers 27-30
U-Tube 13
Vacuum 9, 21, 26, 33
Partial 12,13
Vacuum Breaker 22, 24
Vaporization 15
Waterborne Diseases
Amebic Dysentery 1
Badllary Dysentery 4, 5
Brucellosis 3
Gastroenteritis 4-7
Hepatitis 7
Poliomyelitis 5
Shigellosis 7
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