WATER
SUPPLY
AND
PLUMBING
CROSS-
CONNECTIONS
HAZARDS
IN HOUSEHOLD
AND COMMUNITY
SYSTEMS
;
U. S. ENVIRONMENTAL PROTECTION AGENCY
-------
Statement From Chairman, Joint Committee on Backflow Preventers of the
American Water Works Association and the Conference of State Sanitary
Engineers
January 11, 1963.
DIVISION OF ENVIRONMENTAL
ENGINEERING AND FOOD PROTECTION,
U.S. Public Health Service,
Washington 25, D.C.
GENTLEMEN : I greatly appreciate the opportunity in getting a preview of
your cross-connection control manual. I believe this step is a long one forward
in the battle against unprotected cross-connections. In my opinion, the manual
will certainly be of great use to all who are concerned with this problem, either
as a health department official, as a water purveyor, or as a water user. It is
well written and clearly sets forth the dangers and problems involved in the
efforts to keep water distribution systems free from health hazards. It will
be of definite help to those water purveyors who are waging this battle in their
own community.
Sincerely,
RAY L. DERBY,
Chairman, Joint Committee on
Backflow Preventers, 8210-J.
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HOUSEHOLD AND COMMUNITY
A MANUAL OF RECOMMENDED CONTROL PRACTICES,
INCLUDIN6 A RECOMMENDED ORDI NANCE
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Programs
Water Supply Programs Division
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Public Health Service Publication No. 957
First Printed Feb. 1963
Reprinted May 1966
Reprinted September 1969
Reprinted Nov. 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington D.C. 30402 - Price 40 cents
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FOREWORD
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 sup-
plies should have cross-connection control programs. Those respon-
sible for institutional or semipublic water supplies also should be
familiar with the dangers, and should exercise careful surveillance.
WATER SUPPLY AND PLUMBING CROSS-CONNEC-
TIONS, has been designed and produced as a tool for health officials,
water works personnel, plumbers and many others. It is the result
of many years experience in this field and may be used in educational,
administrative and technical ways in conducting cross-connection
control programs. It was produced under the direction of Mr. Floyd
B. Taylor. The writer of the text and designer of illustrations was Mr.
Marvin T. Skodje, Professor of Sanitary Engineering at North Dakota
State University who is a Public Health Service reserve officer. Chap-
ter II, 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 by the publication.
The manual has been reviewed by members of the Joint Commit-
tee on Backflow Preventers of the American Water Works Associa-
tion and the Conference of State Sanitary Engineers.
ill
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CONTENTS
Chapter Paw
Foreword III
1 Purpose and Scope 1
2 Public Health Significance of Gross-Connections 3
3 Theory of Backflow and Bacfcstphonage 8
4 Methods and Devices for Backflow Prevention 21
5 Testing Procedures for Backflow Preventers 34
6 Protection of PuWlc Water Supply 38
7 Administration of a Cross-Connection Control Program 40
8 Cross-connection Control Ordinance.! 43
Appendixes
A Partial List of Plumbing Hazards 62
B Illustrations of Backslphonage 63
C Illustrations of Backflow 68
D Illustrations of Air Gaps 62
E Glossary 66
P Bibliography 68
G Sample Cross-Connection Survey Form 67
Index 69
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ILLUSTRATIONS
Figure Page
1 Pressure Exerted by One Foot of Water at Sea Level 9
2 Pressure Exerted by Two Feet of Water at Sea Level 10
3 Pressure on the Free Surface of a Liquid at Sea Level 11
4 Effect of Evacuating Air From a Column 12
6 Effect of Evacuating Air From a Column 13
6 Pressure Relationships at Different Elevations in a Continuous
Fluid System 14
7 Pressure Relationships at Different Elevations in a Continuous
Fluid System.. 15
8 Siphon Action in a Plumbing System 16
9 Negative Pressures Created by Constricted Flow 16
10 Dynamically Reduced Pipe Pressures 17
11 Valved Connection Between Potable Water and Non-Potable
Fluid 18
12 Valved Connection Between Potable Water and Sanitary Sewer 19
13 Air-Gap on Lavatory 22
14 Surge Tank and Booster Pump 23
15 Hydro-Pneumatic Booster System 24
10 House Booster System 25
17 Operation of a Vacuum Breaker 27
18 Typical Non-Pressure Type Vacuum Breaker Installation 28
19 Pressure Type Vacuum Breaker 29
20 Reduced Pressure Zone Backflow Preventer 30
21 Swing Connection 30
22 Vacuum Breakers 31
23 Vacuum Breaker Arrangement for Outside Hose Hydrant 32
24 Fire System Make-Up Tank for a Dual Water System 33
25 Reduced Pressure Principle Backflow Preventer Field Test 34
26 Method of Testing Check Valves 37
27 Back Siphonage—Case 1 53
28 Back Siphonage—Case 2 54
29 Back Siphonage—Case 3 55
30 Back Siphonage—Case 4 56
31 Back Siphonage—Case 5 57
32 Back Siphonage—Case 6 58
33 Back Flow—Case 1 59
34 .Back Flow—Case 2 59
35 Back Flow—Case 3 60
36 Back Flow—Case 4 61
37 Air-Gap to Sewer Subject to Backpressure 62
38 Air-Gap to Sewer Subject to Backpressure 62
39 Anti-Splash, Anti-Siphon Arrangement 63
40 Drain Funnel Air-Gap 64
vi
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Chapter 1. PURPOSE AND SCOPE
Public health officials have long been concerned about cross-connec-
tions 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 occurred in
Chicago in 1933. As later proved, old, defective and improperly de-
signed plumbing fixtures and plumbing permitted the contamination
of drinking water. As a result, 1,409 people came down with amoebic
dysentery. There were 98 deaths. This epidemic and others resulting
from contamination introduced into public water-supply through im-
proper plumbing, made clear the responsibility of public health officials
and water purveyors for exercising control over public water distribu-
tion systems and all plumbing systems connected to them. This re-
sponsibility includes advising and instructing plumbing installers in
the recognition and elimination of cross-connections.
Cross-connections and backflow connections are the links through
which it is possible for contaminating materials to enter a potable
water supply. The probability of contamination of drinking water
through a cross-connection occurring within a single plumbing sys-
tem may seem remote, but considering the multitude of similar systems
the probability is great. The only proper precaution is to eliminate all
possible links or channels whereby such pollution may occur.
Why do such cross-connections exist ?
One reason is that a connection is made by a plumbing installer
without an awareness of the danger. He does not realize that water-
flow may occur in a reverse direction, or even uphill. A second reason
why such connections are made is the simple one of convenience, com-
bined with a false reliance on a valve or other mechanical device as an
adequate protection. Valves may fail or be carelessly left open.
To combat the dangers of cross-connections and backflow connec-
tions, education in the dangers of them is needed. First, installers of
plumbing must know that hydraulic and pollutional factors may com-
bine 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 which may be sub-
stituted for the convenient but dangerous direct connection. And
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third, it should be made clear to all that the hazards resulting from
direct connections greatly outweigh the "convenience" gained.
This manual has been designed for use as an instructional guide. It
does not describe all the cross-connections possible in piping systems.
It does attempt to reduce the subject to a statement of the principles
involved and to make it clear to the reader that such installations are
potentially dangerous. The primary purpose is to define, describe,
and illustrate typical cross-connections and to suggest simple methods
and devices by which they may be eliminated without interfering with
the functions of plumbing or water supply distribution systems.
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Chapter 2.—PUBLIC HEALTH SIGNIFICANCE OF
CROSS CONNECTIONS
According to the official investigation of the 1933 Chicago epidemic
of amoebic dysentery,". . . old and generally defective plumbing and
cross-connections potentially permitting backsiphonage from fixtures
such as bathtubs and toilets" . . . were to blame for contamination of
drinking water supply.
The event and its sod result—the death of 98 persons—dramatized
the concern which 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 so general, it is practically a certainty that similar
tragedies will occur again unless more cities take preventive action.
Enteric infections caused by drinking water that has become con-
taminated through cross-connections, may occur in almost any city,
on any day. How do these events happen ?
Reversal of Pressure
A cross-connection is a link or channel between pipes carrying
polluted water and pipes carrying drinking water. The contaminant
enters the potable water system when pressure from the polluted
source exceeds pressure on the drinking water. The action may be
called backsiphonage, or backflow. Essentially it is simply a reversal
of hydraulic pressure 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-con-
nections may appear in many subtle forms and in unsuspected places.
Reversal of pressure in the water may be freakish and unpredictable.
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 midwestern university reported
remittent fevers, malaise, headache, and anemia. Their symptoms led
to a diagnosis of undulnnt fever {brucellosis). Curiously, only those
students who had been working in the cultivation of bacteria in one
3
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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, 1 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 frost-proof hy-
drants and two frost-proof 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 from two autopsies
diagnosed the illness as baeillary dysentery. In addition to the wide-
spread 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 under-
took 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 oubreak of intestinal dis-
turbances 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 water-
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lines 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 weed killer containing arsenic.
Sometime while he was at the job, the water pressure reversed. Tak-
ing no notice of the incident, the man disconnected the hose and, feel-
ing 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 a
high rate of absenteeism. When it was discovered that 25 to 40 per-
cent of the employees were suffering from gastroenteritis, the plumb-
ing 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 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
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
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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 ocean-going 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 of 1962 prescribe the very low
amount of 0.05 parts per million as the limit which 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
About 2 p.m. on June 29, I960, 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 "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 equip-
ment, 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 distribu-
tion system. This system was cross-connected to the city water supply
lines and it was estimated that over 100 gallons of 60 percent ethylene
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glyool 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 ppm of this toxic chemical agent. A homeowner
reported a bitter taste and reddish color to the water department.
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 7:00 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 tem-
porary cross connection had been made between the potable water
lines and pipes containing river water for fire fighting 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 foregoing incidents illustrate why public health officials
earnestly caution builders, plumbers, maintenance men, and city
planners on the correct design and installation of plumbing facilities.
Even more important than the new installations are the many estab-
lished systems which deserve review and correction.
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Chapter 3. THEORY OF BACKFLOW AND
BACKSIPHONAGE
A CROSS-CONNECTION* is the link or channel connecting a
source of pollution with a potable water supply. The polluting sub-
stance, 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 FORCE must act TOWARD the potable supply.
Detecting and eliminating cross-connections may be difficult. First,
the link between the source of pollution and the potable supply may
be much more subtle than a solid pipe connection. Second, the factors
which might produce a reversal of the normal direction of flow may
appear extremely remote or even impossible.
An understanding of the principles of backflow and backsiphonage,
requires an understanding of terms frequently used. FORCE, unless
completely resisted, will produce motion. The direction of the motion
is always the same as that of the force. A force may occur in several
forms, but the form of prime concern in backflow is that of PRES-
SURE. Pressure normally refers to a force per unit area, such as
pounds per square inch. WEIGHT is a special type of force result-
ing from the action of gravity which produces a pressure towards the
center of the earth. The pressure is commonly expressed in pounds
per square inch (psi) and may be referred to an "absolute" scale (psia)
where the "zero" represents absolute vacuum, or to a "gage" scale
(psig) where the "zero*' represents the atmospheric pressure. AT-
MOSPHERIC PRESURE is that pressure exerted by the weight of
the atmosphere above the earth. At sea level it is approximately 14.7
pounds per square inch absolute. The term VACUUM refers to a
negative gage pressure, or that amount of absolute, negative, differ-
ential pressure existing between a contained fluid and the surrounding
atmosphere. The maximum complete vacuum which can be created
at sea level is about 14.7 psi. Since it is nearly impossible to produce
a complete vacuum, the term vacuum used herein will be assumed to
include all degrees of partial vacuum. The pressures exerted by a
fluid while at "rest" will be referred to as STATIC PRESSURE.
1 See formal definition In the glossary of the appendix.
8
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BACKSIPHONAGE l is siphon action in an undesirable or reverse
direction. Ii is caused by the fnnr <>f atmospheric pressure exerted
against a pollutant liquid forcing i: towards a potable water supply
system which is under a negative pressure, or vacuum. P.ACK-
FLOW, although literally meaning any type of reversed flow, will
hereafter generally refer to the flow produced by the differentia] pres-
sure existing between two systems both of which are at pressures
greater than atmospheric (i.e., where negative pressures are not pres-
ent). Backsiphonage is usually less understood than this type of
backflow.
SI PI K )X THEORY. For an under-standing of the nature of pres-
sure fore*1 and its relationship to height, consider the pressure exerted
on the base of a cubic ft of water at sea level. (See figure 1.) The
average weight of a cubic foot of wat.er is (l'J.4 pounds per cubic foot.
The pressure exerted upon the square foot area, is therefore, 62.4
pounds gage pressure. The base may be subdivided into 1 11 square
inches with each subdivision Ix'ing subjected to a pressure of 0.433
pounds.
Suppose another cubic foot of water were placed directly on top of
the. first. (See figure -!.) The pressure on the top surface of the first
cuUi which was originally atmospheric, or 0 psig, would now be 0.4.13
psig as a result of the superimposed cubic foot of water. The pressure
Pressure Exerted by One Foot
of Water at Sea Level
_ 0.433 ps.i.g.
FlUURK 1
Sn formal definition In the glo8«ary of the appendix.
9
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at the base of I lie first ruin1 would also he inc leased by the same amount
to n.siit'i [i>i^r, or t \vo times the original pressure.
Pressure Exerted by Two Feet
of Water at Sea Level
0433 p.s.i.g.
0866 p.s.i.g.
PIOUKF. '1
Tf this process were repeated with a third ruhir foot of water, the
pressures at the Iwstv of each cul>e would lx> l.ii!>'J psi«r, O.SI'.r, psi feet hijrli was equal to -JO
psi<;, the pressure at the water service would he approximately (>'.',.'.'.
\>~-\iS. If the pi'es>iire at the water service was changed suddenly to
• \-\.-\ psi«r, the water pres-ure at the upper tap would reduce to a riejra
tive pn-ssure <»t ~ lo psi^r, or the water in the piping system would
drop to a lower level.
Another illustration, figure :'., de[>icts, -absolute" pressure on the
10
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surface of :i liquid :it sea level. An open tube is inserted vertically
into the. liquid so th:vt (lie. atmospheric pressure acts equally on the
surface of the liquid within (lie tube and on the outside of the tube.
The atmospheric pressure is considered to be 14.7 psia.
Pressure on the Free Surface
of a Liquid at Sea Level
14.7
PSIA
4
'
i
•
14.7
PSI
*
14-7
PSIA
f
Seo Level
FIGUBE 3
If the tuln- is tightly capped and u vacuum pump is used to evacuate
the air from the sealed tube, n total vacuum or a pressure of absolute
xe.ro is created within the tnl>e. Because the pressure at any point in
a static fluid is dependent upon the height of that point above a ivf
crence line, such as sea level, it follows that the pressure within the
tube at M-a level must still be 1 1.7 psia. This is equivalent to the pres-
sure at the base of a column of water ;>.">.'.) feet high and with the
column open at the base, water would rise to till the column to a
depth of :W.!l feet.
Another way of illustrating the rise of water up the tube is to
demonstrate that the, weight of the, atmosphere at sea level exactly
balances the weight of .'-I feet of water as shown in figure .V
In the column of water in figure 1 the absolute pressure within the
at a height of 11.5 feet is equal to 1>.T psia. This represents a
11
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Effect of Evacuating Air from a Column
L "Zero" Absolute Pressure
Fu;t UK 1
of .'» pound.-. PIT square inch In-low atmospheric pn\ssun-, or
:i vacuum of .") pM.
[n the cases cited, the liquid was at iv.-.i and not in motion and the
pn-ssiiivsi-.\i-rt»-d tlu-ivfoiv :irt- st:iiic ]»r«'.ssun--. Tin- pressures exerted
l.v fluids in inotii>n :uv .-jilh-.l DYNAMIC I'll KSSl K KS. It is not
fivisiMr to include in this ni:inii;il M di>ciissioii of I In- more complicated
relationships and laws for calculating tin- |>n'-.-m-r MI a point within
a moving liquid. It will sullicr to >ay thai tin' fluid will move in ;i
direct ion tondin^r to product- a stahle or stal ic slat*-.
12
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Effect of Evacuating Air from a Column
1
Atmospheric Water
Pressure Column
14.7
PSIA
* I
5
i
i
i
14'
r
FIGURE 5
The following diagram (figure. 6) is of an inverted "U" tube which
has been tilled with water and placed in two open containers at sea
level.
If the open containers are placed so that the liquid levels in earh
container are at. the same height, a static state will exist; and the
vacuum at any level in either leg of the. "I " tube may be calculated
as l>efore.
The equilibrium condition is altered by raising one of the containers
so that the liquid level in one container is .". feet above the level of the
other. (See figure 7.) Since both containers are open to the atmos-
phere, the pressure on the liquid surfaces in each container will still
remain at about 14.7 psia. However, a static condition cannot exist
in this instance, since under static conditions the same pressure, will
exist in a continuous liquid only if the two points are at the same
elevation above sea level. The fluid will, therefore, move toward a
static state (i.e., where the free surfaces in each container are at the
same level).
One met .hod of determining the How within the tube may be demon
strated if it is assumed that a static state exists, momentarily, within
the system and the degree of vacuum that exists at a point in the left.
tube from the height of the point al>ove the free surface in the lc.fi
container is calculated. The degree of vacuum which would exist in
this static, state at the corresponding level in the right tul>e above the
13
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Pressure Relationships at Different Elevations
in a Continuous Fluid System
-10 PSIG
FlGl'KK observed thai the decree of vacuum at this point, and at
all levels of the left tul>e, would I*' greater than at corresponding
levels in 11m right tul>e. Since the flow of fluid is from the higher
pressure, (o iht- lo\\er pressure, the flow would he from the right tube
to the left, tube. This arrangement, will he recount i/cd -is a sinhon.
Naturally, water flows ^/"//v»/////.• hut with the aid of u siphon it may
also How orct1 the hill with the additional help of the atmospheric
pressure. The crest of the siphon, however, ciinnol, ideally, Ix1 higher
than .'!! feet above the upper liquid surface since the atmosphere can-
not support a column of water greater in height than 34 feet.
Figure S illustrates how this siphon principle can be hazardous in
a plumbing system. Atmospheric pressure acts at the open faucet and
also at the water dosel which is located at a higher elevation. If the
supply valve is closed, the degree of vacuum in the line supplying the.
faucet is greater at all levels than the vacuum in the supply line to the
water clo
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Pressure Relationships at Different Elevations
in a Continuous Fluid System
FIGURE 7
The siphon actions cited have been produced by reduced pressures
or vacuum result ing from a difference in the water levels at two sep-
arated points within a continuous fluid system. It should also be
noted that reduced pressure may also lie created within a fluid system
as a result of dynamic pressures. One of the basic principles of fluids
as well as of other forms of matter is the principle of conservation of
energy. Based upon this principle, it may he shown that as a fluid
accelerates, as shown in figure !), the pressure is reduced. As water
flows through a constriction such as a converging section of pipe, the
speed of the water is increased; but as a result, the pressure is reduced.
Under possible Circumstances, negative pressures may be developed in
a pip*1. The simple aspirator is bused upon this principle. If this
point of reduced pressure is linked to a source of pollution, backsi-
phonage of the pollutant can occur.
One of the common occurrences of dynamically reduced pipe pres-
sures is found on the suction side of a pump. In many cases similar
to the one illustrated in figure 10, 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
15
-------
Siphon Action in o Plumbing System
14.7
PSIA
FlQURK H
Negative Pressures Created
by Constricted Flow
FIGURE 9
16
-------
Dynamically Reduced Pipe Pressures
I
From
Pollution
Source
Booster Pump
Fl'rlKE 10
the pipe may be increased by a further reduction in pressure at the
pump intake. This often results in the rival ion of negat ive pressures.
This negative ])ressure may become low enough in some cast's to cause,
vaporization of the water in the line. Actually, in the illustration
shown, flow from the source of pollution wouhl occur when pressure.
on the suction side of I lie pump was less than pressure of the pollu-
tion source but this-is BACK FLOW 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 pro-
duce backsiphonage. In addition to the negat ive pressure or reversed
force which is necessary to cause backsiphonage and backflow, there
must, also be the cross-connection or connecting link between the
potable, water supply and the source of pollution. Two basic types
of connections may l>e created in piping systems. These are the
SOLID IMI'K \\iih valved connection and the Sl'BM KR(J KI> IN-
LET. Figures 11 and 1'2 illustrate solid connections. This type of
connection is often installed where it is nece^ary to supply an
auxiliary piping system from the potable source. It is a direct
connection of one pipe to another pipe or receptacle.
Solid pip»- connect ions are often made to continuous or intermittent
waste lines where it is assumed that the How will IM> in one direction
only. An example of ibis would be used cooling water from a water
jacket or condenser a*- shown in figure 12. 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
17
-------
Valved Connection Between Potable
Water and Non- Potable Fluid
r
______ .
Non-
Potable
Potable
FIGURE 11
questioning, however, many installers will agree that the solid con-
nection \vas made localise the sewer is occasionally subjected to
bark pressure.
Submerged inlets are found on many common plumbing fixtures
and are soinet lines necessary feat i ires of the. lixt ures if I hey are to func-
tion properly. Examples of this type of design are siphon-jet urinals
or \valer closets, Mushing rim slop sinks and dental cuspidors. Old
style hathttihs and lavatories had supply inlets below the flood level
rims hut modern sanitary design has minimi/.ed or eliminated this
hazard in new fixtures. Chemical and industrial process vats some-
times have submerged inlets where the water pressure is used as an
aid in diffusion, dispei-sion, and agitation of the vat contents. Even
though t lie supply pipe may come from the floor above the vat, back-
siphonage can occur as it has been shown thai the siphon action can
raise, a liquid such as water almost .'U feet. Some submerged inlets
difficult, to control are those which are not apparent until a significant
18
-------
Valved Connection Between Potable
Water and Sanitary Sewer
City
Supply Condenser
^H
't
J^-IC ^^•«»«U4|WBjaif:-V*J*'. • •<,**'**
••. ..-..-. • • • . .-•-.. • • .•-•
Sanitary Sewer
FIGURE 12
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 !><• rivaled in numerous ways, and
its detection in some of these subtle forms may be difficult
The illustrations included in part B of the appendix are intended
to describe typical examples of backsiphonage, showing in each case
the nature of the link or cross-connect ion, and t he cause of the negative
pressure.
BACKFLOW.1 Backflow, as described in this manual, refers to
reversed How 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 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 hark pressure may he caused l>y gas or steam pressure
from a lx>iler. A differential pressure may
-------
potable system is reduced, by some means, 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 backflow under pressure can occur, describing the cross-
connection and the cause of the reversed flow.
20
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Chapter 4.—METHODS AND DEVICES FOR THE
PREVENTION OF BACKFLOW AND BACK-
SIPHONAGE
The control of fire necessitates the removal of one of the three re-
quirements for combustion, namely, fuel, oxygen, or heat. The con-
trol of backflow requires the removal of one of the two essential factors,
namely, the physical link, or the cause of the reversed pressure
gradient (i.e., the pressure reduction in the reversed direction). The,
removal of the link, or cross-connection, is a positive means of pre-
venting backflow. However, the proper operation of some fixtures,
such as the siphon-yet water closet, requires the link in the form of a
submerged inlet. There are NO cases where the cross-connection
CANNOT be removed or corrected, and the solution which will pro-
vide adequate safety to health should be chosen.
AIR GAP SEPAEATION. The only absolute means of eliminat-
ing the physical link is through the use of the vertical air gap, as illus-
trated by figure 13 (Page 22). Air gaps should be used wherever
possible, and where used must not be bypassed.
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 opening* of the fixture. 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,
a properly installed vacuum breaker should also be provided.
Some minimum air gaps for internally used plumbing fixtures are
shown in the following table excerpted from the National Plumbing
Code ASA A40.8-1955.
Minimum airyaps for internally used, plumbing fixtures
Fixture
Lavatories and other fixtures with effective openings not greater than H-ln.
diameter . .
Sink, laundry trays, goose-neck bath faucets and other fixtures with effective
openings not greater than ?4-in. diameter __
Over rim bath fillers and other fixtures with effective openings not greater
than 1-ln. diameter „. ..
Drinking water fountains— single orifice 7A» (0.437) in. diameter or multiple
orifices having total area of 0.160 sq. in. (area of circle H«-in. diameter)
Effective openings greater than 1 in
Minimum alrgap
When not
affected by
near wall1
(Inches)
1.0
1.8
2.0
1.0
(«)
When af-
fected by
near wall •
(Inches)
l.BO
2.25
3.0
1.60
(«)
i Side walb, 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.
* Vertical walls, ribs, or similar obstructions extending from the water surface to or above the horizontal
plane of the spout dpenlng require a greater alrgap 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 de-
termined. In such cases, the airgap shall be measured from the top of the wall.
> 2 times diameter of effective opening.
' 3 times diameter of effective opening,
1 Bee glossary In appendix.
21
-------
Air Gap on Lavatory
Flood Level Rim
FIGURE 13
If an air gap separation is provided at each fixture, complete pro-
tection 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. However, this protects only the munic-
ipal water supply system. Where the air gap separation is made
at the building water service entrance, a. single surge tank is often
used. The single surge tank, which is illustrated in figure 14,
consists of a reservoir and pump combination with the potable water
supply to the reservoir delivered through an air gap. The surge
tank is used often in installations where water is needed in industrial
processes. The. potable water piping system supplies the lavatory fix-
tures and drinking fountains while the pumped system may provide
water for industrial processes. Many dual piping systems are not
adequately identified by a color code. A color code system is recom-
mended to help prevent the possibility of the two systems becoming
inadvertently interconnected.
When color marking is used, a green color should be used for potable
waterlines and a yellow color for nonpotable waterlines. As painting
22
-------
long st ri'd-la's of pipe may be costly and diflicult, color bands, 3 inches
wide may IH> applied at intervals which should not exceed 2") feet.
Tim pipes should also he handed on both sides of points where they
pass through walls or ceilings.
SI 'R(JF TA XKS. The surge tank may be used to serve single fix-
tures or equipment units, or entire house systems. The si/e of each
unit is determined by the \vat«>r demand rate which it is to accom-
modate. The rate of flow into the receiving reservoir of the simple
surge, tank- shown in figure 14 is governed by the float valve. The
booster pump draws suction from the reservoir, or surge tank, and
discharges diredly 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 properly
covered to prevent contamination.
Surge Tank and Booster Pump
Butterfly
Valve
To Chemical Process
or other Non-Potoble
Use Fixture
Potable Water
Mm 2 Diomeler*
\\\\\\\N\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
An elaboration on the simple surge tank is the combination surge
tank and hydropneumatic tank shown in figure lf>. The addition of
the hydropneumatic tank provides additional pressurized storage
permitting the use of a slightly smaller capacity booster pump in E
terns where the demand rate of the system is not uniform. The use of
an air compressor a!n> permits longer intervals U'tween cycles of
pump operation.
HOOSTKR SYSTKMS. 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
23
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Hydro-Pneumatic
Booster System
To System
'
Air Compressor Serving only
Hydro-Pneumatic Tank
Float
Valve
Hydro-Pneumatic Tank
—rr
\ Float
' Valve
Fn;i ui ir.
there is always ihe possibility of creat inir :i negative pressure in the
water main, as shown in liirure -J^ of appendix IV A simple sur city \valrr pi-cssun- which otlu-r
\\ isc. ini^ht he a\ ailahlc, is lost through t lie air ira|>. Also (hei-e is t lie
haxanl of introducing contamination thmiiirh tin- >ui-r pump su«-l ion
to prevent the pump from civ«tin«r negative pressures in the main,
hut operators find it convenient to shunt around such a switch if there
is any interruption in service. Figure 16 illustrates a positive method
of ne«rat i ve pressure control, which at (lie same t line permits I he direct
use of city pressure when the pressure is adequate.
When the city pressure is sufficient, the Ix.oytei pump is operated
with full city pressure applied to the intake side of the pump. An
altitude, or pressure reducing valve, is installed helow the reservoir
to minimize the required res«'i-\<>ir heijrht. If the ]ire
-------
House Booster System
Screened Vent
a Low Water Level
[Cut-off Swilch
Ifi
VACII'M HKKAKKKS. A fundamental factor in baeksiphon-
ajje, its outlined in chapter :;, is vacuum of negative pressure. If at-
mospheric pressure is admitted to a piping system between u source of
pollution and the origin of tbe vacuum, backsiphonage will be pre-
vented. This is the fund ion of a vacuum breaker. Because a vacuum
may be creali-d at numerous places in a piping system, a vacuum
breaker must be located as near as possible to the fixture from which
contamination is ant icipated. The position of a vacuum breaker must
be siiflicirntly above the fixture flood level rim so that fldin«r or Sllb-
inerjfence of the vacuum lu-eakcr <»•• backpressure cannot occur.
25
-------
Two types of vacuum breakers have been developed. One is de-
signed to be installed on the pressurized distribution system. This
device is called a pressure type vacuum breaker, as it is designed to
be operable even after having remained under hydrostatic pressure for
extended periods of time. The other is called the non-pressure-type
vacuum breaker. The nonpressure type vacuum breaker must always
be installed on the atmospheric side of the fixture valve. The in-
stallation of a vacuum breaker on the atmospheric side of the last con-
trol valve is always preferred over the use of a pressure type vacuum
breaker.
The operation of one type, nonpressure. vacuum breaker is illus-
trated in figure 17. The device in this instance is installed on a flush-
ometer valve water closet with the flushometer valve located directly
above the vacuum breaker and the flood level rim of the Avater closet
located at least six inches below the vacuum breaker. When the
flushometer valve is operated, the flow of water is downward and the
disc is in the normal, vertically seated position, preventing water from
spilling out of the pipe. If a negative pressure should develop on the
supply line to the fixture, atmospheric pressure would be exerted on
the disc and within the supply line above the flood level rim, thus pre-
venting backsiphonage from the water closet. This action is illus-
trated by views 2 & 3. The vacuum breaker IS NOT designed to
provide protection against backflow resulting from BACKPRES-
SURE and shoiild not be installed where backpressure may occur.
Figure 18 shows another nonpressure type vacuum breaker installa-
tion. The serrated outlet laboratory sink supply might easily be ex-
tended by a hose to a point below the flood level rim of the laboratory
sink thus producing a cross-connection. The vacuum breaker installa-
tion on the atmospheric side of the control valve and between the
cross-connection and the control valve effectively protects the piping
system against backsiphonage. Figures 22 & 23 show other types.
The pressure type vacuum breaker operates on the reverse principle
of the non-pressure type in that the moving parts do not complete a
full cycle of operation each time the fixture or supply line is used.
The principle of operation is shown in figure 19. The device is
designed to open permitting the admission of air to satisfy the vacuum
when & negative head occurs in the supply line. It does not provide
protection in the case of backflow resulting from backpressure. Such
devices have limited application as a positive protection against back-
flow and should be used only on specific authorization of the adminis-
trative authority having jurisdiction.
26
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Operation of a Vacuum Breaker
Disc
Disc in Normal
Flow Position
Atmospheric
Pressure
Vacuum
Atmospheric 7^
Pressure
IN. Atmospheric
Pressure
Vacuum Flow Just after
Vacuum is Applied
Atmospheric
Pressure
Disc in Vacuum
Breaking Position
UK 17
KKIMVKD 1'KKSSIKK I'KINCII'LK HACKFLOYV I'KK
YKNTKlt. The pressure and nonpressure type vacuum breakers are
designed to prevent backsiphonage only and cannot he installed \\lioro
l>ark|)n>ssuivs urr liki'ly to oc<-iir. In situations \\lu-rc it would !*•
cxtirni^ly difficult, to provide a physical l»n>ak In't \v«H'ii two systems
ami where backpressures ran lx> cxptscttnl. a reduced pn-ssmv prin-
ciple, hackllow prt-VfMilei- can he used. This di-v'nv consists of two,
hydraulic-ally or mechanically loaded, pressure reducing, check valves
with a [injure regulated relief valve located between the two check
valves as shown by li^utv i>o.
Flow from the left enters the central cliamU'r against the presi-'Uiv
exerted by the loaded check valve uumU-r 1. The sup[)ly pressuie is
reduce*! thereupon by a predetermined amount. The pressuiv in the
27
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Typical Non-Pressure Type
Vacuum Breaker Installation
Vacuum
Breaker
FIGURE 18
central chamber is maintained lower ihan the incoming supply pres-
sure through the operation of the relief valve number .">, which dis-
charges to the, atmosphere whenever the central chaml>er pressure-
approaches within a few pounds of the inlet pressure. Check valve
number '2 is lijrhtly loaded to open with a pressure drop of 1 psi in
the direction of flow and is independent, of the pressure required to
open the relief valve. In the event that the pressure increases down
stream from the device, tending to reverse the direction of flow, check
valve number 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 suflieient. If some obstruction prevents
check valve number 2 from closing tightly, the leakage hack into the
central chamber would increase, the pressure in this zone, the relief
valve would open, and flow would IK>. 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 numlxT .'5 should remain
fully open to the atmosphere to discharge any water which may be
28
-------
Pressure-Type Vacuum Breaker
(Not Applicable Where
Back-Pressure May Occur)
Atmospheric x
Pressure u
Normal Flow
Vacuum
Vacuum Condition
NOTE' This shows the principle of operation Other types
have a sliding spool which closes the air inlet when
there is forward flow
,•*•<] to l.ackflou as a result of I >ac|< pressure ;ui.
Malfunctioning of one 01- \H\\\\ of the check valves or n-lief valve
should al\\;iys In- indicated liy ;i discharge of water from (hf relief
port. This factor is an important advaiitanv mcr carli(>r l)ackflo\v
di^ircs. The pressure loss through tin- dc\'ice may lie expecteil to
average between 1" and 'JO pounds per square inch within the normal
raiiLre of ciperat ion,depending ii|)on the si/e and How rate of the device.
hori'.LK CIIKCK VALVK ASSKMI'.I.V AND OTIIKK
METHODS. Other methods and devices have heen pronu»ted for
the separation of auxiliary systems or for the prevention of haekllow.
Amonir these are I he single cliiM-k valve, the plain donhle <-lu'<-k valve
assembly, the donhle check valve douhle
-------
Reduced Pressure Zone Bockflow Preventer
{Principle of Operation)
0
o
i !
Normal Direction of Flow Reversed Direction of Flow
KH.I ui L'f>
Swing Connection
31
Potable Supply
Swinging
Ball Joint
Not recommended without additional
acceptable backflow preventer
Fn.i in L'l
,'iO
-------
Vacuum Breakers
Rubber
Sleeve
Flush
Connection
Cowl Nut
Vacuum Closes Gate
*Air Enters
Here Pre-
venting Rise
of Contamin-
ated Liquids
in Fixtures
Air Vent
B
FIGURE 22
subject to wear ;iml interference resulting from deposits and other
factors, the single check valve is not considered an adequate back flow
preventer. Double check valve, assemblies in scries, including1 those
with spacers and manual bleed valves, have similar disadvantages.
The advantage oll'ered 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, sho\vn in Figure '2(1,
is a very useful and, when properly maintained, reliable means of
back-flow protection for intermediate decrees of hazard. Frequently
refe.rred to as the Factory-Mutual assembly, this device had been in
service at some plants since (he early IJXlO's. As in the case of other
biickflow preventers, the double chdck-double ^ate valve assembly
should be. ins|H'<'.twl at, re^ulai' intervals. Some health authorities
have established programs of annual ins|x>ction.
The double check-double <;ate system has the advantage of a low
head loss. With the jrate. \alves widti open the two checks, when in
open posit ion, oll'er little, resistance to (low.
31
-------
Vacuum Breaker Arrangement for Outside Hose Hydrant
NOTE-
(7) '/2"or V4" Gate Valve
(|) i/2"ar3/4"Sch. 40. Galv.
(3) '/a"011 W Vacuum Breaker
0 i/2"or3/4"EII. M, I. Galv.
© Exterior Building Wall
©("Sleeve, Sch.40
(?) Handwheel
(§) IPS Hose Adapter
(9) Coupling M.I Galv.
(JO) 1/2" or 3/4" Nipple Galv.
"A"
Plan
~ n H ii.ii
Section A A
Ficrm: I'.",
Double check-double gate assemblies should be well designed and
constructed. The valves should be all bronze or, for larger sizes,
galvanized gray iron. The trim should be of bronze, or other cor-
rosion 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 shown in figure 21 does not offer adequate
protection against bnckflow between the two systems which it inter-
connects. It should not be used to connect a hazardous system to a
potable system without the inclusion of an acceptable means of back-
flow prevent ion.
-------
Fire System Make-up Tank
fora Dual Water System
Non-Potable Supply
Potable Supply
1M
The barometric loop consists of :i vertical loop of pipe extending at
least :'•:» feel above tin- highest fixture. The principle is that a com-
plete vacuum » MII i mi raise water to an elevntioii ^rcairr 1 1 i:m ."».'). '.i fcci .
'I'liM ilfviri-. however, does not provide protect ion a-jfainst bnckflow due
to liuckpressure and (lie installation of a pipe loop of this height is
usually dillicult and expensive. As a result il is not widely n-ed.
Tlie air method, UN -hown in figure iJl,
provides the reliability of having two separate sour<-es of water and
at, the same time adequately protecting the potahle supply against
hackflow from the nonpotable system.
33
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Chapter 5. TESTING PROCEDURES FOR
BACKFLOW PREVENTERS
VACUUM BREAKER, ATMOSPHERIC. Normal failure of
an atmospheric type vacuum breaker is (lie result of a rupture of the
rubber membrane in devices using the rubber check valve, or the
result of damage or failure of the disc in the disc type devices. This
typo of failure is usually accompanied by an excessive weeping or
leakage of the device and can readily be determined through visual
examination. In addition to visual inspection, some of the units
should be disassembled periodically for inspection.
REDUCED PRESSUKK PRINCIPLE BACKFLOW PHK-
VENTER. The reduced pressure principle backflow installation
should include a ti
-------
Four threaded %-inch test cocks should be installed as indicated in
figure 25. Additional equipment required to conduct the tests is as
follows:
1. One—Compound gage capable of indicating a vacuum equal to
30 inches of mercury or about 15 psi.
2. One—Plastic tube 1 inch O.D. x %-inch I.D. x 6 inches long
with an adapter to ^-inch pipe thread and a i/^-inch street ell.
3. One—Plastic tube as above; 12 inches long with adapter and
street ell.
4. One—Compound gage and connecting piping with drain cock
as shown on the diagram.
5. One—Eight-foot length of ^4-inch hose with an adapter to
V4-inch pipe.
In the operation of the RPPBP, the reduced pressure zone between
the two check values is maintained at a pressure less than the supply
line pressure by the action of the 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. Both check valves should close
tightly against backflow under adverse pressure differentials.
TEST PROCEDURE. Attach equipment as shown in the
diagram.
A. Close gate valve No. 2. If the relief valve starts to drain,
the first check valve is leaking.
B. Close gate valve No. 1.
C. Open test cock No. 4 to fill the plastic tube, and crack open
gate valve No. 1, until a small dribble continues over the top
of the tube.
D. Open test cock No. 3. Water will then spill over the top of
the short tube.
E. Open test cock No. 2.
F. Open the drain cock No. 1 slowly until the spillage over the
top of the short tube stops. Check the gage reading at
this point. This reading is the pressure drop across the first
check valve and should be not less than 6 psi nor more than
11 psi.
G. Slowly open the drain cock, thereby causing the gage pres-
sure to fall.
H. As the gage pressure approaches 2 psi, the water column in
tube No. 3 will slowly fall, and should rapidly fall, just as the
relief valve opens. (In valves 6 hiches and larger, it may be
necessary to refill tube with hose.) The gage reading at this
point should not be less than 2 psi.
I. Open the drain cock wide, causing relief valve to open wide.
35
-------
J. If the water level in the tube at test cock No. 4 remains at top
of tube, the check valve No. 2 is tight. If the water level falls
when the relief valve is open, refill No. 4 tube with the hose
and maintain the water level at the top of the tube. If the
relief valve drains continually, the second check valve is
leaking. If there is no drainage from the relief valve, but
flow through the hose is required to maintain water level in
the No. 4 tube, then the second gate valve is leaking.
DOUBLE CHECK-DOUBLE GATE VALVES
The double check-double gate valve assembly should include test,
hose-bibbs as shown in figure 26. A method for testing the check
valves is as follows:
A. WHERE BACK-PRESSURE IS AVAILABLE ON
PRIVATE SUPPLY
1. Open all Test Hose Bibbs individually to flush out any sedi-
ment or scale.
2. Close Gate Valves A and G.
3. Open Test Hose Bibbs B and F, successively. If leakage occurs,
Gate Valve(s) A and/or G are leaking and must be repaired
before continuing test.
4. If no leakage at Test Hose Bibbs B and F with Gate Valves A
and G closed, proceed with the following:
a. Open Gate Valve G and Test Hose Bibb D. If leakage does
not cease, Check Valve E is leaking and must be repaired. If
leakage ceases, Check Valve E is tight.
&. Temporarily connect a hose between Test Hose Bibbs D and
F and open these Hose Bibbs. Open Test Hose Bibb 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 Hose Bibbs 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 Hose Bibbs individually to flush out any sedi-
ment or scale.
2. Close Gate Valves A and G.
3. Open Test Hose Bibbs B and F, successively. If leakage
occurs, Gate Valve(s) A and/or G are leaking and must be
repaired before continuing test.
36
-------
Method of Testing Check Valves
Public
Supply
Private
Supply
Test Hose
Bibb
B
Tes1 Hose
Bibb
Test Hose
Bibb
KII.IRK 'J.
If leakage does not cease, Check Valve E is leaking and must
be repaired. If leakage ceases, Check Valve E is tight.
b. Close Hose Bibbs J and F. Temporarily connect the hose
I Hit "\vecu Test Hose Bibbs ,) and 1) and open these Test
Hose Bibbs. Open Test Hose Bibb B. If leakage does
not, cease, Check Valve C is leaking and must be repaired.
If no leakage occurs, Check Valve Cist ight.
c. If Check Valves are repaired, repeat the test as above.
5. When the test is complete, close Test Hose Bibbs and remove
t he hose. Leave Gate Valves A and G in their proper position.
37
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Chapter 6. PROTECTION OF PUBLIC WATER
SUPPLY
Public water supply distribution systems must be protected against
the hazards of contamination of the potable water in the pipes. The
text thus far has dealt mainly with the subject of building plumbing
but frequent reference has also been made to the main water supply
system. Other health hazards affecting a community water supply
distribution system include the following types.
1. Direct connection to an auxiliary piping system carrying non-
potable water. Example : Some municipalities have a separate
water distribution system containing untreated river water for
fire fighting. There are recorded instances where the potable
and nonpotable systems were directly connected with only a
valve separating them.
2. Connection to a well water pump system containing nonpotable
or questionable water.
3. Fire hydrants with weep holes are a hazard. Note: It is diffi-
cult to obtain from a fire hydrant a water sample free from
coliform organisms.
4. Interconnections with other public water supply systems sup-
posed to contain potable water but which actually do not.
5. Connections to premises such as industrial establishments, ship-
yards, docks, abbatoirs, and others where major contamination
of water can take place and the polluted water be forced or
sucked back into the public water supply distribution system.
6. Open reservoirs of finished water are always points where ac-
cidental or covert contamination of water can occur.
7. Inadequately sized piping in a public water supply system sets
the stage for the reduced pressures and negative head condi-
tions conducive to backflow and backsiphonage.
Water supply and public health officials should assure themselves
that hazards of the above or other types are eliminated or safely con-
trolled. The preceding text has dealt with methods of protecting
water service lines on a premise. The requirement of an air gap 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.
38
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The appearance of fire hydrants without weep holes holds promise
but filling hydrant risers with toxic antifreeze solutions should be
prohibited as should their use in sprinkler systems.
Direct connections between potable and nonpotable water supply
systems should be eliminated or properly protected and intercon-
nections with other public water supply systems should be permitted
only with the approval of health authorities.
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 in which it is needed. 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.
Private wells should have no connection to the potable, public water
supply system. Open reservoirs should be covered or, where this is
not possible, auxiliary chlorination should be provided.
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 dis-
infecting repaired and new pipe sections should be observed.
39
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Chapter 7. ADMINISTRATION OF A CROSS
CONNECTION CONTROL PROGRAM
RESPONSIBILITY. Public health personnel, water works offi-
cials, 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 plumb-
ing systems and encourage as well as assist in the training of persons
responsible for their installation and maintenance. Officials respon-
sible for the inspection of plumbing installations should require the
maximum protection against backflow which is consistent with good
judgement and the public safety. Plumbing installers and mainte-
nance 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.
Water works 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. Water
works officials often prescribe the installation of a backflow prevention
device in the service line to a premise where hazardous use of water is
found.
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 repair. 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 haz-
ard of the contaminant and the probability of reversed flow.
40
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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 NON-
POTABLE WATER. All such connections should be broken
IMMEDIATELY and properly protected.
Obsolete fixtures, such as tubs and lavatories, having inlets termi-
nating 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 fix-
tures should be replaced on a systematic, improvement basis. Fix-
tures which 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.
METHOD OF ACTION. A broad program of cross-connection
control should include INSTRUCTION, INSPECTION, AND IM-
PROVEMENT or NEW INSTALLATION. Methods applied to
new installations, however, are different from those applied to existing
plumbing systems. Control of NEW INSTALLATIONS should be
accomplished through PLAN REVIEW AND INSTALLATION
INSPECTION. Control and elimination of EXISTING HAZ-
ARDS should be accomplished through ROUTINE INSPECTION
AND PERIODIC SURVEYS at definite intervals. Trained person-
nel, competent in plan examination and hazard evaluation, should
supervise the control program. Sanitary inspectors who have quali-
fications equivalent to licensed plumbers and who have been specially
instructed 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
41
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improvement, or lack of improvement, be noted. Through a sum-
marization 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.
42
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Chapter 8. CROSS-CONNECTION CONTROL
ORDINANCE PROVISIONS
INTRODUCTION
The successful promotion of a cross-connection and backflow con-
nection 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 which will establish a program of inspection for
an elimination of cross and backflow connections within the commu-
nity. Frequently authority for such a program may already be pos-
sessed by the water department or water authority. In such cases no
further document may be needed. A cross-connection control ordi-
nance 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, and
3. Penalty provisions for violations.
The following simple form is suggested for municipalities who desire
to adopt a cross-connection control ordinance. The technical provi-
sions are excerpted from a revision of the National Plumbing Code
prepared by the Public Health Service Technical Committee on
Plumbing Standards. Where the National Plumbing Code or sub-
sequent revisions thereof is in effect, the technical sections of the fol-
lowing can be replaced by a statement of reference to the Code. Com-
munities adopting ordinances should check with State Health Officials
to assure conformance with state codes. The form of the ordinance
should comply with local legal requirements.
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 judg-
ment may be necessary to ensure that such plumbing has been installed
in such a manner as f o 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 or authorized agent of the
43
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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 is 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 provided 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 in-
vested with the authority and responsibility for the enactment and
enforcement of this ordinance.
2.2 Air Gap. The unobstructed vertical distance through the free
atmosphere between the lowest opening from any pipe or faucet sup-
plying water to a tank, plumbing fixture, or other device and the flood
level rim of the receptacle.
2.f3 Approved. Accepted by the Agency as meeting an applicable
specification 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 city water supply which may be available in the building or
premises.
2.5 Backflow. The flow of water or other liquids, mixtures or sub-
stances 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 Backftow Preventer. A device or means to prevent backflow.
2.7 Baclcxiphonage. The flowing back of used, contaminated or
polluted water from a plumbing fixture or vessel or other sources into
a water supply pipe due to a negative pressure in such pipe.
2.8 Barometric Loop. A loop of pipe rising approximately 35
feet, at its topmost point, above the highest fixture it supplies.
2.9 Check Valve. An automatically operated device which is de-
signed to permit the flow of fluids in one direction and to close if there
is a reversal of flow.
2.10 Oontamination. See pollution.
2.11 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,
steam, gases or chemicals whereby there may be a flow from one system
to the other. See BACKFLOW AND BACKSIPHONAGE.
44
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2.12 Drain. Any pipe which carries waste water or water-borne
wastes in a building drainage system.
2.13 Fixture, Plumbing. Installed receptacles, devices, or appli-
ances supplied with water or which receive or discharge liquids or
liquid-borne wastes.
2.14 Flood Level Rim. The edge of the receptacle from which
water overflows.
2.15 Hazard, Health. Any conditions, devices, or practices in the
water supply system and its operation which create, or, in the judg-
ment of the Director, may create, a danger to the health and well-
being of the water consumer. An example of a health hazard is a
structural defect in the water supply system, whether of location,
design, or construction, which may regularly or occasionally 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 Hydropneumatic Tank. A pressure vessel in which air pres-
sure 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 distribu-
tion pipes, plumbing fixtures and traps; soil, waste, and vent pipes;
building drains and building sewers including their respective con-
nections, devices, and appurtenances 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 which tends to degrade
its quality so as to constitute a hazard or impair the usefulness of the
water.
2.21 Reduced Pressure Principle Backfiow Preventer. An as-
sembly of differential valves and check valves including an auto-
matically 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
which is designed so as not to be subjected to static line pressure.
2.25 Vacuum Breaker, Prewure Type. A vacuum breaker
designed to operate under conditions of static line pressure.
2.26 Water, Potable. Any water which, according to recognized
standards, is safe for human consumption.
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2.27 Water, Nonpotable. Water which is not safe for human con-
sumption or which 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 system.
3.2 Gross-Connection* Prohibited* Cross-connections between
potable water systems and other systems or equipment containing
water or other substances of unknown or questionable safety are pro-
hibited 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 pub-
lie 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 boiler
feed water systems in which boiler water conditioning chemicals are
introduced shall be made through an nirgap or provided with an
approved backflow preventer * located in the potable waterline before
the point where such chemicals are introduced.
3.6 Prohibited Connections to Fixtures and Equipment. Connec-
tion to the potable water supply system for the following is pro-
hibited unless protected against backflow in accordance with Section
3.8 or as set out herein.
(a) Bidets.
(&) 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.
(
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ant, with two separate thickness of metal separating the refrigerant
from the potable water supply, 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 poinLof installation shall be
provided if the refrigeration units contain more than 20 pounds of
refrigerants.
3.8 Protection Against Backflow and Backsipkonage.
3.81 Wafer 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 § 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
(6) Back-flow Preventer: An approved backflow preventer device
or vacuum breaker to prevent the drawing of contamination into the
potable water system.
3.82 Minim/urn Required Airgap. (a) How Measured: The mini-
mum required airgap shall be measured vertically 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 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, "Minimum
Airgaps for Generally Used Plumbing Fixtures."
TABLE 3.S2.—Minimum alrgapt for generally used plumUng fixtures
Fixture
Lavatories and other fixtures with effective openings not greater than H-ln.
diameter ....... ..j. .
Sink, laundry trays, goose-neck bath faucets and other fixtures with effective
openings not greater than W-ln. diameter ... .
Over rim hath fillers and other fixtures with effective -openings not greater
than 1-ln, diameter.. .. . ....... ..... ...
Drinking water fountains— single orifice 7/16 (0.437) In. diameter or multiple
orifices having total area or 0.150 sq. in. (area of circle Mt-to. diameter)
Effective openings greater than 1 Inch. .,,....„......
Minimum airgap
When not
affected by
near wall '
(inches)
1.0
1.5
3.0
1.0
CO
When
affected by
near wall '
(laches)
I.M
2.25
3.0
1,50
(<>
i Bide well*, ribs, or similar obstructions do not affect alrgaps when spaced from Inside edge of spout
opening a distance ureater 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.
* Vertical walls, ribs, or similar obstructions extending from the water surface to or above the horicontal
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 alrgap shall be measured from the top of the wall.
* 2 times diameter of effective opening.
* 8 times diameter of effective opening.
47
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3.83 Approval of Devise*. 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 dis-
tribution 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 Inxtallation 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 equipment
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.
(&) Reduced Preamire Principle Backflow Preventer; A reduced
pressure principle type backflow preventer may be installed subject to
full static pressure.
(c) Devices of all Type*: 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, pro-
vided they are readily accessible, is also permitted.
3.85 Tanks and Vatx-Relo\v 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,
"Sizes of Overflow Pipes for Water Supply Tanks", the overflow pipe
shall be provided with an airgap as close to the tank as possible.
TABLE 3.85.—Kizcn of overflow pipes for water supply tanks
Maximum capacity of water
supply line to tank
0-50 epm
50-150 (tpm...
100-200 Rpm
200-400 gpm.
Diameter of
overflow
pipe (Inches
ID)
2
2W
3
4
Maximum capacity of water
supply line to tank
400-700 Kpm
700-1 000 pprn
Over 1,000 Epm.
Dlam«ter of
overflow
pipe (Inches
ID)
5
6
8
The potable water outlet to the tank or vat shall terminate a
distance not less thnn !*/£ 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.
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3.86 Protective Devices Required. Approved devices to protect
against backflow and backsiphonajje 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 Back Pressure : "Where a water con-
nection is not subject to back pressure, a nonpressure type vacuum
breaker shall be installed on the discharge side of the last valve on the
line serving the fixture or equipment. A list of some conditions re-
quiring protective devices of this kind is given in Table 3.86A, "Cross-
Connections Where Protective Devices are Required and Critical
(G-L) Settings for Backflow Preventers".
TABLE 3.86A. — Cross-connectiona where protective devices are required and criti-
oatlevel (C-L) settings for backflow prevent era *
Fixture or equipment Method of installation
Aspirators and ejectors ----------- C-L at least 6 In. above flood level of re-
ceptacle served.
Dental units _____________________ On models without built-in vacuum
breakers — C-L at least 0 In. above flood
level rim of bowl,
Dishwashing machines ----------- C-L at least 6 in. above flood level of ma-
chine. JnstaH on both hot and cold water
supply line.
Fhwhotneters (closet & urinal} — C-L at least 6 in. above top of fixture
supplies.
Garbage can cleaning machine ---- C-L at least 6 in, above flood level of ma-
chine. Install on both hot and cold water
supply lines.
Hose outlets ----- ---------------- C-L at least 6 Sn. above highest point on
hose line.
Laundry machines -------------- C-L at least C In, above flood level of ma-
chine. Install on both hot and cold water
supply lines.
Lawn sprinklers ----------------- C-L at least 12 In. above highest sprinkler
or discharge outlet
Steam tables -------------------- C-L at least 6 in. above flood leveL
Tank and vats ------------------- C-L at least 8 in. above flood level rim or
line.
Trough urinals ------------------ C-L at least 30 In. above perforated flush
pipe.
Flush tanks --------------------- Equip with approved ball cock. Where ball
cocks touch tank ^yat«r equip with vacuum
breaker at least 1 In. above overflow out-
lets. Where ball cock does not touch tank*
water install ball code outlet at least 1 In.
above overflow outlet or provide vacuum
breaker as specified above.
Hose bibbs (where aspirators or C-L at least 6 In. above flood level of re-
ejectors could be connected) . ceptacle served.
J Critical Level
-------
(b) Connections Subject to Back Pressure: Where a potable water
connection is made to a line, fixture, tank, vat, pump, or other equip-
ment with a hazard of backflow or backsiphonage where the water con-
nection 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, "Partial List of Cross-Connections Subject to
Back Pressure".
TABLE 3.86B.—'Partial list of cross-connections which may te subject to back
pressure.
Chemical lines Pumps
Dock water outlets Steam lines
Individual water supplies Swimming pools
Industrial process water lines Tank and vats—Bottom Inlets
Pressure tanks 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 provided with a barometric loop. Barometric loops
shall precede the point of connection.
3.88 Double Check-Double Gate Valve*. The Director may au-
thorize installation of approved, double check-double gate valve as-
semblies with test cocks as protective devices against backflow in con-
nections 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 Outoff 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 neg-
ative 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 build-
ing and premise owners to maintain all backflow preventers and
vacuum breakers within the building or on the premises in good work-
ing order and to make no piping or other arrangements for the pur-
pose of bypassing backflow devices.
4.2 Reduced Pressure Principle Back-flow) Preventers. Periodic
testing and inspection schedules shall be established by the Director
for all reduced pressure type preventers and the interval between such
testing and inspections and overhauls of each device shall be estab-
lished in accordance with the age and condition of the device. Inspec-
tion intervals should not exceed 1 year, and overhaul intervals should
50
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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 terminated, and/or recom-
mend such additional fines or penalties to be invoked as herein may be
provided.
5.2 Fines. The owner or authorized agent of the owner respon-
sible 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
violation. 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
Garbage can washer
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!<•<> in.-i!
|.almraliir\ sink, si-rratP*! no/.y.l<>
I ..i iliiili .v u.ai-llinr
l.;i rnturj
l.awn sprinkler syMnn
riii'ln lal»>ral"ry sink
Sc\\ t-r lliisliin^ niaiiliolf
Ship sink, tlu-liin^ rim
Slop sink. Ilirradcd sii|>ii|y
SK-ain lahlt-
I riual. -i|tliiiii jet liln\v mil
VN'atiT i-li isi -I, llll-tl lank, hall
\\':tii-r rlnx-i. Itn-^li valve. n jfl
APPENDIX H
Tin- following IKI.UI-S illustrate typical pluinliiim installations \vlieiv ;
Back Siphonage-Case I
HHRHH
ja_H_fi_B_iBj
H H H H
BfcLHH H H
l-'i'.i i;i -J7
-------
A. CONTACT I'niNT: A rul>l>er hi«sc is submerged iii ;i bedpan \\asli sink.
H. CAI'SKS KI.OVV: ill A sterili/.er coime« -led to the water
supply is allowed i<> rue.I williiiiit oj»eiiiiifr the air vent. As it cools. Ihe pres-
sure w it hiM the sealed >terili/er drops In-low iilinusplierii- prixliK-iiii; :i v:ieiiillii
which draws the polluted waier iiii<> the sterili/.er fontaminntlng il< ci.ment^
•2) The Hushing of several llush valve toilet*, nn a inwer floor \\-hich are con-
• •(1 to an undersized water service line reduces (lie pressure at the water
closets to atmospheric producing M IT versa 1 of I he llou.
«'. SrC<:KSTI':i» <'• IKKKCTII >.\ : The water .'oniie.-lion at the bed pan wash sink
should he provided with a properly installed haekllmv preventer and also the
sterilizer.
Back Siphonage-Case 2
nnn
nnnnnn
FlGURK
A. CONTACT POINT: A rubber hose is submerged in a laboratory sink.
It. CAI Si: OF Hi:\ i:i£SKI> KI.<>\\-: Tuoop|K,siu. muliistory buildings are con-
nected to the same water main which often lacks adequate pressure. The
building on the right has installed a booster pump. When the pressure is in-
adequate in the main, the building booster pump starts pumping, producing a
negative pressure In (lie main and causing a reversal of Mow in the opposite
building.
54
-------
(' SI <;<;i:STKI> CnUUKrTloN : The laboratory sink water outlet shoijld be
provided \viili ;i vacuum breaker. Tin- wafer service line to tin- booster puinti
should In- equipped \\itli ;i device in cul utT ilie pinup when pressure ap-
proaches a negative head nr vjicuuni.
Back Siphonage-Case 3
KIM-UK 2!)
A. Ci INTACT I'nl.XT: A chemical lank has a suit merged inlet.
H. CAISKOF UKVKHSKli Fl.n\V: The plain fire pump draws suotion directly
from the city \\aler supply line \vliich is insufficient to serve nuriinil plant re-
quireiuents and :i major lire at the same time. IHirinu a lire emer^eiu-y. re-
versed tlo\v niiiv occur within the plant.
C. SI <;i;i:STKI> CoRHHCTKlX : The water service t<» the chemical tank should
tie provided through an nirsrap.
55
-------
Back Siphonage-Case 4
_ High x-»
^Service Low
Service
Fn;riiK
A. CONTACT I'OINT: The water supply in th«> dishwasher is nut protected by
a vannim breaker. Also, the dishwasher h;is ,-i solid waste COIIIKH I inn |u
lln- M-U -
I!. CAISi; OK ItKVKUSKI) KI.o\V : Tl«- nii
-------
line. I Miring periods of low city pressure. Ihe I sler punip sudimi creates
negative pressures ill (he |i>\\ --.vstem, llierehy reversing Ihe tlow.
C. SI <;i I KSTKI» <'< >UUK<'Tl< »N : The dishwasher 1ml :nul ••••Id water should
he ^upplied Ihroiiuh ;in air^ap :ind I lie \\.-isle from llie dishu asher slniuld
discharge through an indireei \\asie. The booster pump should he equipped
\\ ii 11 a [<>\\ pressure ruin IT device.
Back Siphonaqe - Case
Mam
B.
FK,i KI: ."-I
A. CONTACT I'oIXT: The ^asnliue st..mm- tiink is maintained full and under
pressure hy means of a direct connection n> the city water dist rihni ion
system.
i; CA1SI-: i iF I{l':\'i:KSI-:i > KI.< >\V : Casoline may enter the dist rilnil ion system
l)\ j;ravity or hy siphoiui^e in Ihe event <»f :i le;ik or break in the water
in.-iin.
C sr<:<:i:STKI i CoRIJKCTHtN : A reduced pressure principle h;ickllnw pre-
venter should he installed in the line lo Ihe gasoline storage tank or a s
tank and pump should he provided in thai line.
57
-------
Back Siphonage - Case 6
A. CONTACT POINT: Then- is a sul.mcrnt-d inlet in the srroml Hour Imtlmili.
H, CAISK OF KKYKUSK1) FLOW: An automobile breaks n nearby Jiiv-hyf \vati-r anil a n»%C!itiv«> iin-ssiuv in thi' scrvici- lin<- l<. the
liousf. siickint dirty w;it»-r out i>f tin- Imtliliili.
C. srCdKSTKh CoItllllC'I'Ii >.\ : Tin- h..i nti.l cold uali-r inlcls to the l.atlitnl.
Slllllllll )><• IllmVc [lie rill) of till- I 111).
APPENDIX C
Tli«- fo||i»win« pjisri-s arc illustrations of typicnl plumhinK instnllatioiis wln-n-
n-sultinj,' from hackpn-ssurc is possible.
58
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Bock Flow - Case I
Ch«micol
JL
F*«dti
»
FIGURE 33
A CONTACT POINT: A direct ,-onm-dion from the city supply to Hie hoiler
exists jis a s:ifi-t\ measure iiiul fur Idling the system. The holler water
system is Hicniirjilly treated fur s.-:ile pre\ ml inn and corrosinn n.ntrol.
I: r.vi SK (il-1 Hi:\ KUSDIi FLOW : The hniler wilier reein-nliK ion pump (lis-
eh:irtre pressure or hitckpressure from tlu- boiler »'\ceeils ihe city \v;iter
pressure Mini the rlieniii-nlly treate<| water is pumped into the (lomestir .system
IhroiiKh ail open or leaky valve.
('. SI CCKSTKIi roKKKCTloV: As miniiiiuin protection t\v<. check valve- in
si-ries should he provided in the mnkeup waterline to the boiler system. An
air k';
-------
\ ( 'i iN'I'.M "]' I'OIXT: Sewage seeping from :l resii lent i;i ] ress] ..... 1 pollutes
I he private well whii-li is used for hi\vn sprinkling. The il<>tnes|je \\ater
s\slem. \\lneli is served from :i eily main. is roimecled In the \\cll siippk hv
moans <>f :\ v;ilvi'. Tin- |ilir|Hisi- nf tin- rniiiiri-l inn m;iy lie !<> ]pl'in.c I hi- \vdl
I-'l.< i\\ : I )in-in« |M-riin|s nf |..\v rily \\alcr |>n--ufr.
|Mi>sllily \\licn liiwn spriiiUlin^ is at ils peak, llic well pump ilisi liar^'c pn--
siin' cMi-cils Iliat UK- ( jty
supply Ihnnmh ;in open or IrjiKy valve.
C. SI <;(;i:STi:i > ri >UUI-:("I'H >.\ : Tlieeon ..... -lion |M-IWCI>II the well waliT :unl
ritV WHler sllnllhl lie druUeli.
Back Flow -Case 3
A. ('(INTACT I'nlXT: A v;ilve eolineclioli exists I.elweetl I he (Milalile and the
nolipiitalile -yslenis alu.ard tin- ship.
15. 1'AI'SK ()(•' Ui:\ I USI-;i» FLOW: While the ship is roinie.-ted to i he eity
water supply system for the purpose of taking mi water for the potable sys-
tem. I lie valve belueeii the polahle and llolipotalile systems i^ opened, per
milting < »n lam ina led \\aler i<> lie pumped i"t" I he in mini pal supply.
c srccisSTI-M > cnHUKi'TION : Kach pier water oiith-i siioiihl he ].i-o|<-.
against haektlow. The laain waier servjee to i he pier should also he jjro|.
afrainst haektluw hy an air yap or reilured pressure prineiple backllow
pre\. -liter.
60
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Back Flow-Case 4
CME WOOLEN MILLS j
- -
. • r
Sprinkler System
*- ^
LU
FI..I
A CONTACT I'Ul.NT: A sinirle valved eonncet inn exists between tin- |.ul>li<.
pntahle water .sii|i])ly ami the tiro-sprinkler system of a mill.
]t. CAISK «>K Ki:\ KKSKI* I l.n\V: Tlie sprinkler system is iiurin;illy siiiiplit>(l
from ;l jn-;irl>\ hike llirmmli ;i hi.Lrli pressure pump. Alioiit the hike ;i re
•• lillllllx-rs i if ovi'l-lliiwin^ M-ptie l.-inkv.. \Vhcli the xulve is left uj-.-ii
i-i'iit:iniin:ite4l hike Wilier r:m he plllupiil tu the pillilii sllpj
«'. SI
-------
APPENDIX D
The fnllowinj,' illustrations dcsi rihc methods of providing ;ni air trap
ID a waste line wliirli may In- occasionally or continuously Mibjccl to liar
Air Gap to Sewer Subject
to Backpressure
Bali-
Check
Force Main
I-'IM KK :i7
Air Gap to Sewer Subject
to Backpressure
2XD
Indirect Waste
Ball-Check
Horizontal Waste
Gravity Drain
FlCUKK :
-------
The following illustrations describe methods by which air gap protection may
lie in hievcd and splashing reduced.
Anti-Splash, Anti-Siphon
Arrangement
x^ ^
f , A
£J
', .,
2" Mox.
^Boll- I
L>n6CK 2XD
1
Flow
FIGURE 39
XOTK—Where D is less tlnui 2 inches, a vacuum breaker may be substituted for
the hall-check device.
63
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Drain Funnel Air Gap
Pipe"A"
Braze
Pipe Nipple
Braze
Pipe Coupling
1/2 * 1/3" Strap.
3 Equally Spaced
Minimum
Funnel
Drain Pipe"C"
Drain Funnel
Pipe "A"
Dimcn'.'B"
Pipe "C"
'/e"
l-'/2
1
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APPENDIX E—GLOSSARY
Airgap
The unobstructed vertical distance through the free atmosphere between the
lowest opening from any pipe or faucet supplying water to a tank, plumbing
fixture, or other device and the flood level rim of the receptacle.
ttackflow
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 tyi>e of backflow.
Backflow Connection
Any arrangement whereby backflow can occur.
Backflow Preventer
A device or means to prevent backflow.
nackflow Preventer, Reduced Pressure Principle Type
An assembly of differential valves and check valves including an automatically
opened spillage port to the atmosphere.
Backsiphonage
The flowing back of used, contaminated, or polluted water from a plumbing
fixture or vessel or other sources Into a water supply pipe due to a negative
pressure in such pipe.
Cross-Con neotion
Any physical connection or arrangement between two otherwise separate pip-
ing systems, one of which contains potable water and the other either water of
unknown or questionable safety or steam, gas, or chemical whereby there may
be a flow from one system to the other, the direction of flow depending on the
pressure differential between the two systems. See Backflmo and Backsiphonaae.
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.
Flush ometer Valve
A device which discharges a predetermined quantity of water to fixtures for
flushing purposes and Is actuated by direct water pressure.
Frostproof Closet
A hopper with no water In the bowl and with the trap and water supply con-
trol valve located below frost line.
Indirect Waste Pipe
A drain pipe used to convey liquid wastes which does not connect directly
with the drainage system, but which discharges into the drainage system through
an air break Into a vented trap or a proi>erly vented and trapped fixture, recep-
tacle, or interceptor.
Nonpotatlc Water
Water not safe for drinking, personal, or culinary use.
65
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Plumbing
The practice, materials, and fixtures used in the installation, maintenance,
extension, and alteration of all pining, fixtures, appliances, and appurtenances in
connection with tiny of the following: Sanitary drainage or storm drainage
facilities, the venting system and the public or private water-supply systems,
within or adjacent to any building structure, or conveyance; also the practice
and materials used in the installation, maintenance, extension, or alteration of
storm water, liquid waste, or sewerage, and water-supply systems of any
premises to their connection with any point of public disposal or other acceptable
terminal.
Potable Water
Water free from impurities present in amounts sufficient to cause disease or
harmful physiological effects. Its bacteriological and chemical quality shall
conform to the requirements of the Public Health Service Drinking Water
Standards or the regulation of the public health authority having jurisdiction.
Vacuum
Any pressure less than that exerted by the atmosphere.
Vacuum Breaker
See Backftow Preventer.
Vacuum Breaker, Nonprcssure Type
A vacuum breaker which is not designed to be subjected to static line pressure.
Vacuum Breaker, Pressure Type
A vacuum breaker designed to operate under conditions of static line pressure.
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 con-
necting 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 F—BIBLIOGRAPHY
Control and Elimination of Cross-Connections, Panel Discussion, Journal Amer-
ican Water Works Association, vol. 50, No. 1, January 1960.
Specifications and Manual of Cross-Connection Control Practice Committee,
Southern California Water Utilities Association, Manual of Cross-Connection
Control Recommended Practice, Research Foundation for Cross-Connection
Control, University of Southern California, Los Angeles 7, Calif., August 1060.
Regulation* ftrlatinff To Crogtt-Connfctionn, excerpt from the California Admin-
istrative Code, title 17, Public Health 1056.
How To Prevent Industrial Cross-Connection Dangers, Water Works Engineer-
ing, February 1062.
66
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Michael, Jerrold M., The Theory and Methods of Prevention of Backsiphonage
and Croaa-Connectiona, Public Health Service, Communicable Disease Center,
Training Branch, Atlanta, Ga., 1959. With reference bibliography of 10 items
not repeated here.
Springer, E. K. and Reynolds, K. C., Definitions and Specifications of Double
Check Valve Assemblies and Reduced Pressure Principle BacJcftow Prevention
Devices, University of Southern California, School of Engineering Report
4&-101, 30 January 1959.
Angele, Gustave J., Cross-Connections: Their Prevention and Control In The
Y-12 Plant of Union Carbide Nuclear Company At Oak Ridge, Tennessee.
Write to author, Union Carbide Nuclear Co., P.O. Box Y, Oak Ridge, Tenn.
Use of Back flow Preventers For Cross-connection Control, Joint Committee
Report, Journal American Water Works Association, v. 50, No. 12, December
1958.
A Revision Of The National Plumbing Code, ASA A^O.8-1955, Report of the
Public Health Service Technical Committee On Plumbing Standards. Sept 15,
1962. Public Health Service, Washington 25, D.O.
Taylor, F. B. and Skodje, M. T., Cross Connections, A Hazard in All Buildings,
Modern Sanitation and Building Maintenance, v. 14, No. 8, August 1962.
Dawson, P. M. and Kalinske, A. A., Report On Cross-Connections and Back-
Slphonage Research, Technical Bulletin No. 1, National Association of Plumb-
ing, Healing, Cooling Contractors, Washington, D.C.
Cross Connection Complications, the Capital's Health, v. II, No. 9, Dec. 1953,
D.C. Dept. of Public Health, Washington, D.O.
APPENDIX G
The following IB a sample cross-connection survey form.
CROSS-CONNECTION SURVEY FORM
Place: _ Date: .._
Location: Investigator(s):
Building Representative (s) and Title (s):
Water Source (s):
Piping System (s): _ _
Points of Interconnection:.
Special Equipment Supplied with Water & Source:
67
-------
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 head-
ings
Description of
Rovm Numbtr Cntt Connection ft)
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INDEX
Page
Administration 40,42
Air binding 24
Air gap 21,22
Antifreeze 6,39
Arsenic 5
Backflow 9,17,20
Backflow preventer, reduced
pressure 28
Backpressure . 27
Backsiphonage 9
Barometric loop 82,33
Booster system:
house 25
hydropneumatlc 24,25
Brucellosis 3,4
Builders 7
Check valve:
double — 31,82
single 81
Chemicals 41
Chicago outbreak 1,3
Chlorides 6
Chromates ; 6
Color coding 22,23
Compressor, air 23,24
Contaminant 3
Disease ill
Double check-double gate valves- 81,32
Dual piping 20,22
Dysentery:
amoebic 1,3
baclllary 4,6
Education 111,1,40
Effective opening 21
Ethyiene glycol 6
Flood level rim
Frost-proof hydrants.
Frost-proof toilets™
18
4
4
Gastroenteritis 4,5,7
Harbor water 4,6
Hazards plumbing 52,63
Health hazards 40
House booster 25
Hydrants, frost proof-
Infections, enteric
Inlet submerged
Inspections —.
Laboratory
Ordinance
Poliomyelitis
Pressure:
absolute
atmospheric
drop
dynamic
gage
loss
reduction
reversal
static
Priorities
Public health officials-
Public water supply __.
Pumps, booster
4
8,4
18,19
31,84
26;28
43-51
5,6
8,11
8
4
12,17
8
31
17
8
8
40,41
7,40
38,89
24
Regional Offices, PHS— Inside Cover
Separation, systems-
Siphon theory
Surge tanks
Swivel connections-
Tanks:
hydropneumatic
surge
Tests:
double check valves —
reduced pressure valves
vacuum breakers
Toxiclty
Training
U-Tube -
Vacuum breakers
non-pressure
pressure
Valves:
defective
ipressure reducing
Weep holes
20,21
9-16
24
32,34
24,25
24
36,87
34,35
36
7
42
18,14
26,27
27
27
4
25
38,39
*U.S,COVHHM£NTPRimi«OfflCfcl971- 759-278/2112. R.gion No. S-II
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ENVIRONMENTAL PROTECTION AGENCY
Office of Water Programs
REGIONAL OFFICES
Region I - Connecticut, Maine,
Massachusetts, New Hampshire,
Rhode Island, Vermont
John F. Kennedy Federal Bldg.
Boston, Massachusetts 02203
Region VI - Arkansas, Louisi-
ana, New Mexico, Ohio,
Texas
1114 Commerce Street
Dallas, Texas 75202
Region II — New Jersey, New
York, Puerto Rico, Virgin Islands
Federal Building
26 Federal Plaza
New York, New York 10007
Region VII — Iowa, Kansas,
Missouri, Nebraska
911 Walnut Street
Kansas City, Missouri 64106
Region III — Delaware, District
of Columbia, Maryland, Penn-
sylvania, Virginia, West Virginia
Curtis Bldg., 6th & Walnut Sts.
Philadelphia, Pennsylvania 19106
Region IV - Alabama, Florida,
Georgia, Kentucky, Mississippi,
North Carolina, South Carolina,
Tennessee
1421 Peachtree St., N.E.
Suite 300
Atlanta, Georgia 30309
Region V — Illinois, Indiana,
Michigan, Minnesota, Ohio
Wisconsin
1 North Wacker Drive
Chicago, Illinois 60606
Region VIII — Colorado,
Montana, North Dakota,
South Dakota, Utah,
Wyoming
1860 Lincoln Street
Lincoln Tower
Denver, Colorado 80202
Region IX - Arizona, Cali-
fornia, Hawaii, Nevada,
Guam, American Samoa,
Trust Territory, Wake
Island
50 Fulton Street
San Francisco, California 94102
Region X - Alaska, Idaho,
Oregon, Washington
1200 Sixth Avenue
Seattle, Washington 98101
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