Cross-Connection

Control Manual
Printed on Recycled Paper

Office of Water (4606M)

EPA 816-R-03-002

www.epa.gov/safewater

February 2003
Cross-Connection

Control Manual

United States

Environmental Protection Agency

Office of Water

Office of Ground Water and Drinking Water

First Printing 1973

Reprinted 1974, 1975

Revised 1989

Reprinted 1995

Technical Corrections 2003
Preface

ii • CROSS-CONNECTION CONTROL MANUAL

Plumbing cross-connections,

which are defined as actual

or potential connections

between a potable and nonpotable water supply, constitute

a serious public health hazard.

There are numerous, welldocumented cases where crossconnections have been responsible for contamination of

drinking water, and have

resulted in the spread of disease.

The problem is a dynamic one,

because piping systems are

continually being installed,

altered, or extended.

Control of cross-connections is possible, but only

through thorough knowledge

and vigilance. Education is

essential, for even those who are

experienced in piping installations fail to recognize crossconnection possibilities and

dangers. All municipalities with

public water supply systems

should have cross-connection

control programs. Those

responsible for institutional or

private water supplies should

also be familiar with the

dangers of cross-connections

and should exercise careful

surveillance of their systems.

This Cross-Connection Control

Manual has been designed as a

tool for health officials, waterworks personnel, plumbers, and

any others involved directly or

indirectly in water supply

distribution systems. It is

intended to be used for educational, administrative, and

technical reference in conducting cross-connection control

programs. This manual is a

revision of an earlier book

entitled Water Supply and

Plumbing Cross-Connections (PHS

Publication Number 957),

which was produced under the

direction of Floyd B. Taylor by

Marvin T. Skodje, who wrote

the text and designed the

illustrations.

Many of the original

illustrations and text have been

retained in this edition. Previous revisions were done by

Peter C. Karalekas, Jr. with

guidance from Roger D. Lee

incorporating suggestions made

by the staff of the EPA Water

Supply Division, other governmental agencies, and interested

individuals.

This 3rd edition was

produced as a result of an

updated need for crossconnection control reference

material reflecting an increase

in cross-connection control

activity throughout the United

States. It has been revised and

re-issued reflecting a demand

for its use, together with

requests for a document that

covers the broad spectrum of

cross-connection control from

both the basic hydraulic

concepts through the inclusion

of a sample program that can

be a guide for a program at the

municipal level. New backflow

devices have been included in

this revision that are now being

produced by manufacturers

reflecting the needs of the

market. Updated actual crossconnection case histories have

been added containing graphic

schematic illustrations showing

how the incidents occurred and

how cross-connection control

practices could be applied to

eliminate future re-occurrence.

A more detailed explanation of

cross-connection control

“containment” practice has

been included together with the

use for “internal backflow

protective devices” and “fixture

outlet protection”.

This 1989 edition was

prepared by Howard D.

Hendrickson, PE, vice president

of Water Service Consultants,

with assistance from Peter C.

Karalekas, Jr. of Region 1, EPA,

Boston.

This latest (2003) edition

has technical corrections

provided by Howard D.

Hendrickson, P.E., showing

updates on pages iv, 18, 23, 30,

31, and 32.
TABLE OF CONTENTS • iii

Contents

American Water Works Association Policy on Cross-Connections . . . . . . . iv

Chapter

1. Purpose & Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. Public Health Significance of Cross-Connections . . . . . . . . . . . . . . . . . 2

3. Theory of Backflow and Backsiphonage . . . . . . . . . . . . . . . . . . . . . . . 12

4. Methods and Devices for the Prevention of Backflow and

Backsiphonage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5. Testing Procedures for Backflow Preventers . . . . . . . . . . . . . . . . . . . 25

6. Administration of a Cross-Connection Control Program . . . . . . . . . . 30

7. Cross-Connection Control Ordinance Provisions . . . . . . . . . . . . . . . . 33

Appendixes

A. Partial list of plumbing hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

B. Illustrations of backsiphonage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

C. Illustrations of backflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

D. Illustrations of air gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

E. Illustrations of vacuum breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

F. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

G. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

H. Sample cross-connection survey form . . . . . . . . . . . . . . . . . . . . . . . . . 44

I. Sample cross-connection test form . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Illustrations

Human blood in the water system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Burned in the shower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Heating system anti-freeze into potable water . . . . . . . . . . . . . . . . . . . . . . . 3

Salty drinks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Paraquat in the water system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Propane gas in the water mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Chlordane and heptachlor at the Housing Authority . . . . . . . . . . . . . . . . . . 5

Boiler water enters high school drinking water . . . . . . . . . . . . . . . . . . . . . . . 6

Pesticide in drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Car wash water in the water main . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Shipyard backflow contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Chlordane in the water main . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Hexavalent chromium in drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Employee health problems due to cross-connection . . . . . . . . . . . . . . . . . . . 9

Dialysis machine contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Creosote in the water mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Kool aid laced with chlordane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure

1 Pressure exerted by one foot of water at sea level . . . . . . . . . . . . . . . . 12

2 Pressure exerted by two feet of water at sea level . . . . . . . . . . . . . . . . 13

3 Pressure on the free surface of a liquid at sea level . . . . . . . . . . . . . . . 13

4 Effect of evacuating air from a column . . . . . . . . . . . . . . . . . . . . . . . . 13

5 Pressure relationships in a continuous fluid system at

the same elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6 Pressure relationships in a continuous fluid system at

 different elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7 Backsiphonage in a plumbing system . . . . . . . . . . . . . . . . . . . . . . . . . 14

8 Negative pressure created by constricted flow . . . . . . . . . . . . . . . . . . 14

9 Dynamically reduced pipe pressure(s) . . . . . . . . . . . . . . . . . . . . . . . . . 14

10 Valved connection between potable water and nonpotable fluid . . . . 15

11 Valved connection between potable water and sanitary sewer . . . . . . 15

12 Air gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

13 Air gap in a piping system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

14 Barometric loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

15 Atmospheric vacuum breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

16 Atmospheric vacuum breaker typical installation . . . . . . . . . . . . . . . . 17

17 Atmospheric vacuum breaker in plumbing supply system . . . . . . . . . 17

18 Hose bibb vacuum breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

19 Typical installation of hose bibb vacuum breaker . . . . . . . . . . . . . . . . 18

20 Pressure vacuum breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

21 Typical agricultural and industrial application of

pressure vacuum breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

22 Double check valve with atmospheric vent . . . . . . . . . . . . . . . . . . . . . 19

23 Residential use of double check with atmospheric vent . . . . . . . . . . . 19

24 Double check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

25 Double check valve detector check . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

26 Residential dual check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

27 Residential installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

28 Copper horn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

29a Reduced pressure zone backflow preventer . . . . . . . . . . . . . . . . . . . . . 21

29b Reduced pressure zone backflow preventer . . . . . . . . . . . . . . . . . . . . . 21

30 Reduced pressure zone backflow preventer principle of operation . . . 22

31 Plating plant installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

32 Car wash installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

33 Typical by-pass configuration, reduced pressure principle devices . . . 23

34 Typical installation, reduced pressure principle device,

horizontal illustration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

35 Typical installation, reduced pressure principle device,

vertical installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

36 Typical installation, double check valve, horizontal and vertical

installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

37 Typical installation, residential dual check with straight

set and copper horn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

38 Pressure vacuum breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

39 Reduced pressure principle backflow preventer, Step 1 . . . . . . . . . . . 27

40 Reduced pressure principle backflow preventer, Step 2 . . . . . . . . . . . 27

41 Double check valve assemblies, Method 1 . . . . . . . . . . . . . . . . . . . . . 28

42 Double check valve assemblies, Method 2 . . . . . . . . . . . . . . . . . . . . . 29

43 Cross-connection protection, commercial, industrial and residential . 30

44 Backsiphonage, Case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

45 Backsiphonage, Case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

46 Backsiphonage, Case 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

47 Backsiphonage, Case 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

48 Backsiphonage, Case 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

49 Backsiphonage, Case 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

50 Backflow Case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

51 Backflow Case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

52 Backflow Case 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

53 Backflow Case 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

54 Air gap to sewer subject to backpressure—force main . . . . . . . . . . . . 41

55 Air gap to sewer subject to backpressure—gravity drain . . . . . . . . . . 41

56 Fire system makeup tank for a dual water system . . . . . . . . . . . . . . . 41

57 Vacuum breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

58 Vacuum breaker arrangement for an outside hose hydrant . . . . . . . . . 41
iv • CROSS-CONNECTION CONTROL MANUAL

An AWWA

Statement of Policy

on Public Water Supply Matters.

Cross Connections

Adopted by the Board of

Directors Jan. 26, 1970,

revised June 24, 1979, reaffirmed June 10, 1984 and

revised Jan. 28, 1990 and Jan.

21, 2001.

The American Water

Works Association (AWWA)

recognizes water purveyors

have the responsibility to

supply potable water to their

customers. In the exercise of

this responsibility, water

purveyors or other responsible authorities must

implement, administer, and

maintain ongoing backflow

prevention and crossconnection control programs

to protect public water

systems from the hazards

originating on the premises

of their customers and from

temporary connections that

may impair or alter the water

in the public water systems.

The return of any water to

the public water system after

the water has been used for

any purpose on the

customer’s premises or

within the customer’s piping

system is unacceptable and

opposed by AWWA.

The water purveyor shall

assure that effective backflow

prevention measures commensurate with the degree of

hazard, are implemented to

ensure continual protection of

the water in the public water

distribution system. Customers,

together with other authorities

are responsible for preventing

contamination of the private

plumbing system under their

control and the associated

protection of the public water

system.

If appropriate back-flow

prevention measures have not

been taken, the water purveyor

shall take or cause to be taken

necessary measures to ensure

that the public water distribution system is protected from

any actual or potential

backflow hazard. Such action

would include the testing,

installation, and continual

assurance of proper operation

and installation of backflowprevention assemblies, devices,

and methods commensurate

with the degree of hazard at the

service connection or at the

point of cross connection or

both. If these actions are not

taken, water service shall

ultimately be eliminated.

To reduce the risk private

plumbing systems pose to the

public water distribution

system, the water purveyor’s

backflow prevention program

should include public education

regarding the hazards backflow

presents to the safety of

drinking water and should

include coordination with the

cross connection efforts of local

authorities, particularly health

and plumbing officials. In areas

lacking a health or plumbing

enforcement agency, the water

purveyor should additionally

promote the health and safety

of private plumbing systems to

protect its customers from the

hazards of backflow.
CHAPTER ONE • 1

Chapter One

Public health officials have

long been concerned

about cross-connections and

backflow connections in

plumbing systems and in public

drinking water supply distribution systems. Such crossconnections, which make

possible the contamination of

potable water, are ever-present

dangers. One example of what

can happen is an epidemic that

occurred in Chicago in 1933.

Old, defective, and improperly

designed plumbing and fixtures

permitted the contamination of

drinking water. As a result.

1,409 persons contracted

amebic dysentery; there were

98 deaths. This epidemic, and

others resulting from contamination introduced into a water

supply through improper

plumbing, made clear the

responsibility of public health

officials and water purveyors for

exercising control over public

water distribution systems and

all plumbing systems connected

to them. This responsibility

includes advising and instructing plumbing installers in the

recognition and elimination of

cross-connections.

Cross-connections are the

links through which it is

possible for contaminating

materials to enter a potable

water supply. The contaminant

enters the potable water system

when the pressure of the

polluted source exceeds the

pressure of the potable source.

The action may be called

backsiphonage or backflow.

Essentially it is reversal of the

hydraulic gradient that can be

produced by a variety of

circumstances.

It might be assumed that

steps for detecting and eliminating cross-connections would

be elementary and obvious.

Actually, cross-connections may

appear in many subtle forms

and in unsuspected places.

Reversal of pressure in the

water may be freakish and

unpredictable. The probability

of contamination of drinking

water through a crossconnection occurring within a

single plumbing system may

seem remote; but, considering

the multitude of similar

systems, the probability is

great.

Why do such

cross-connections

exist?

First, plumbing is frequently

installed by persons who are

unaware of the inherent

dangers of cross-connections.

Second, such connections are

made as a simple matter of

convenience without regard to

the dangerous situation that

might be created. And, third,

they are made with reliance on

inadequate protection such as a

single valve or other mechanical

device.

To combat the dangers of

cross-connections and backflow

connections, education in their

recognition and prevention is

needed. First, plumbing

installers must know that

hydraulic and pollutional

factors may combine to produce

a sanitary hazard if a crossconnection is present. Second,

they must realize that there are

available reliable and simple

standard backflow prevention

devices and methods that may

be substituted for the convenient but dangerous direct

connection. And third, it should

be made clear to all that the

hazards resulting from direct

connections greatly outweigh

the convenience gained. This

manual does not describe all the

cross-connections possible in

piping systems. It does attempt

to reduce the subject to a

statement of the principles

involved and to make it clear to

the reader that such installations are potentially dangerous.

The primary purpose is to

define, describe, and illustrate

typical cross-connections and to

suggest simple methods and

devices by which they may be

eliminated without interfering

with the functions of plumbing

or water supply distribution

systems.

Purpose

and Scope
Chapter Two

Public health officials have

long been aware of the

impact that cross-connections

play as a threat to the public

health. Because plumbing

defects are so frequent and

the opportunity for contaminants to invade the public

drinking water through crossconnections are so general,

enteric illnesses caused by

drinking water may occur at

most any location and at any

time.

The following documented

cases of cross-connection

problems illustrate and

emphasize how actual crossconnections have compromised

the water quality and the public

health.

Human Blood in

the Water System

Health Department officials

cut off the water supply to

a funeral home located in a

large southern city, after it was

determined that human blood

had contaminated the fresh

water supply. City water and

plumbing officials said that they

did not think that the blood

contamination had spread

beyond the building, however,

inspectors were sent into the

neighborhood to check for

possible contamination. The

chief plumbing inspector had

received a telephone call

advising that blood was coming

from drinking fountains within

the building. Plumbing and

county health department

inspectors went to the scene

and found evidence that the

blood had been circulating in

the water system within the

building. They immediately

ordered the building cut off

from the water system at the

meter.

Public Health

Significance of

Cross-Connections

Investigation revealed that

the funeral home had been

using a hydraulic aspirator to

drain fluids from the bodies of

human “remains” as part of the

embalming process. The

aspirator directly connected to

the water supply system at a

faucet outlet located on a sink

in the “preparation” (embalming) room. Water flow through

the aspirator created suction

that was utilized to draw body

fluids through a hose and

needle attached to the suction

side of the aspirator.

The contamination of the

funeral home potable water

supply was caused by a combination of low water pressure in

conjunction with the simultaneous use of the aspirator.

Instead of the body fluids

flowing into the sanitary drain,

they were drawn in the opposite

direction—into the potable

water supply of the funeral

home!

Reverse flow through

aspirator due to

back siphonage

Body fluids

“Hydro”

aspirator

Negative supply pressure

Open

Closed

Closed

Normal operation

Positive supply pressure Potable water Open

2 • CROSS-CONNECTION CONTROL MANUAL
Burned in the

Shower

One neighbor’s head was

covered with blisters after she

washed her hair and others

complained of burned throats

or mouths after drinking the

water.

The incident began after an

8-inch water main, that fed the

town, broke and was repaired.

While repairing the water

main, one workman suffered

leg burns from a chemical in

the water and required medical

treatment. Measurements of the

ph of the water were as high as

13 in some sections of the pipe.

Investigation into the cause

of the problem led to a possible

source of the contamination

from a nearby chemical

company that distributes

chemicals such as sodium

hydroxide. The sodium hydroxide is brought to the plant in

liquid form in bulk tanker

trucks and is transferred to a

holding tank and then pumped

into 55 gallon drums. When

the water main broke, a truck

driver was adding the water

from the bottom of the tank

truck instead of the top, and

sodium hydroxide backsiphoned into the water main.

Heating System

Anti-Freeze into

Potable Water

A resident of a small town in

Alabama, jumped in the

shower at 5 a.m. one morning

in October, 1986, and when he

got out his body was covered

with tiny blisters. “The more I

rubbed it, the worse it got,” the

60 year old resident said. “It

looked like someone took a

blow torch and singed me.”

He and several other

residents received medical

treatment at the emergency

room of the local hospital after

the water system was contaminated with sodium hydroxide, a

strong caustic solution.

Other residents claimed

that, “It (the water) bubbled up

and looked like Alka Seltzer. I

stuck my hand under the faucet

and some blisters came up.”

Chemical bulk storage and holding tanks

“Burned in the shower”

Water main

break and

repair

water service

Hose with bottom fill

Automobile antifreeze

added to boiler water Backsiphonage

(reverse flow)

Normal flow

Curb stop with stop

and waste drain

Water main

Bangor Maine Water

Department employees

discovered poisonous antifreeze

in a homeowner’s heating

system and water supply in

November, 1981. The incident

occurred when they shut off

‘the service line to the home to

make repairs. With the flow of

water to the house cut off,

pressure in the lines in the

house dropped and the antifreeze, placed in the heating

system to prevent freeze-up of

an unused hot water heating

system, drained out of the

heating system into house

water lines, and flowed out to

the street. If it had not been

noticed, it would have entered

the homeowner’s drinking

water when the water pressure

was restored.

CHAPTER TWO • 3
Salt water suction line

for fire protection

Main fresh

water line

Pump prime line

High pressure fire line

Seawater

Backflow preventer

replaced by spool piece

Mixing Sink

Herbicide holding tank

Potable town water

Recommended installation of

backflow preventer

Salty Drinks Paraquat in the

Water System

water supply piping had been

left open. A lethal crossconnection had been created

that permitted the herbicide to

flow into the potable water

supply system. Upon restoration of water pressure, the

herbicides flowed into the many

faucets and outlets on the town

water distribution system.

This cross-connection

created a needless and costly

event that fortunately did not

result in serious illness or loss of

life. Door-to-door public

notification, extensive flushing,

water sample analysis, emergency arrangements to provide

temporary potable water from

tanker trucks, all contributed to

an expensive and unnecessary

town burden.

I

n January, 1981, a nationally

known fast food restaurant

located in southeastern United

States, complained to the water

department that all their soft

drinks were being rejected by

their customers as tasting

“salty.” This included soda

fountain beverages, coffee,

orange juice, etc. An investigation revealed that an adjacent

water customer complained of

salty water occurring simultaneously with the restaurant

incident. This second complaint

came from a water front ship

repair facility that was also

being served by the same water

main lateral. The (investigation

centered on the ship repair

facility and revealed the

following:

• A backflow preventer

that had been installed on the

service line to the shipyard had

frozen and had been replaced

with a spool piece sleeve.

• The shipyard fire

protection system utilized sea

water that was pumped by both

electric and diesel driven

pumps.

• The pumps were primed

by potable city water.

With the potable priming

line left open and the pumps

maintaining pressure in the fire

lines, raw salt water was

pumped through the priming

lines, through the spool sleeve

piece, to the ship repair facility

and the restaurant.

“Yellow gushy stuff”

poured from some of

the faucets in a small town in

Maryland, and the State of

Maryland placed a ban on

drinking the water supply.

Residents were warned not to

use the water for cooking,

bathing, drinking or any other

purpose except for flushing

toilets.

The incident drew widespread attention and made the

local newspapers. In addition to

being the lead story on the

ABC news affiliate in Washington, D.C. and virtually all the

Washington/Baltimore newspapers that evening. The news

media contended that lethal

pesticides may have contaminated the water supply and

among the contaminants was

paraquat, a powerful agricultural herbicide.

The investigation disclosed

that the water pressure in the

town water mains was temporarily reduced due to a water

pump failure in the town water

supply pumping system.

Coincidentally, a gate valve

between a herbicide chemical

holding tank and the town

4 • CROSS-CONNECTION CONTROL MANUAL
Recommended installation

of hose bibb vacuum breaker

backflow preventer

Gate valve closed

Recommended

backflow

preventer

installation

Water main

pressure

65 psi

Explosion

Fire Hose used for 

propane tank

purging cross

connected

to private

fire hydrant

Propane Gas in the

Water Mains

ate repair procedures. To

start the repair, the tank was

“purged” of residual propane

by using water from one of two

private fire hydrants located on

the property. Water purging

is the preferred method of

purging over the use of carbon

dioxide since it is more positive

and will float out any sludge as

well as any gas vapors. The

“purging” consisted of hooking

up a hose to one of the private

fire hydrants located on the

property and initiating flushing

procedures.

Since the vapor pressure of

the propane residual in the tank

was 85 to 90 psi., and the water

pressure was only 65 to 70 psi.,

propane gas backpressure

backflowed into the water

main. It was estimated that the

gas flowed into the water mains

for about 20 minutes and that

about 2,000 cubic feet of gas

was involved. This was approximately enough gas to fill one

mile of an 8-inch water main.

Chlordane and

Heptachlor at the

Housing Authority

of the gate valve. When the

workman cut the 6-inch line,

water started to drain out of the

cut, thereby setting up a

backsiphonage condition. As a

result, the chemicals were

siphoned out of the truck,

through the garden hose, and

into the system, contaminating

the seventy five apartments.

Repeated efforts to clean

and flush the lines were not

satisfactory and it was finally

decided to replace the water

line and all the plumbing that

was affected. There were no

reports of illness, but residents

of the housing authority were

told not to use any tap water

for any purpose and they were

given water that was trucked

into the area by volunteer fire

department personnel. They

were without their normal

water supply for 27 days.

Hundreds of people were

evacuated from their

homes and businesses on an

August afternoon in a town in

Connecticut in 1982 as a result

of propane entering the city

water supply system. Fires were

reported in two homes and the

town water supply was contaminated. One five-room

residence was gutted by a blaze

resulting from propane gas

“bubbling and hissing” from a

bathroom toilet and in another

home a washing machine

explosion blew a woman

against a wall. Residents

throughout the area reported

hissing, bubbling noises,

coming from washing

machines, sinks and toilets.

Faucets sputtered out small

streams of water mixed with

gas and residents in the area

were asked to evacuate their

homes.

This near-disaster occurred

in one, 30,000 gallon capacity

liquid propane tank when the

gas company initiated immediThe services to seventy five

apartments housing

approximately three hundred

people were contaminated with

chlordane and heptachlor in a

city in Pennsylvania, in December, 1980. The insecticides

entered the water supply

system while an exterminating

company was applying them as

a preventative measure against

termites. While the pesticide

contractor was mixing the

chemicals in a tank truck with

water from a garden hose

coming from one of the

apartments, a workman was

cutting into a 6-inch main line

to install a gate valve. The end

of the garden hose was submerged in the tank containing

the pesticides, and at the same

time, the water to the area was

shut off and the lines being

drained prior to the installation

CHAPTER TWO • 5
Boiler Water

Enters High School

Drinking Water

No students or faculty

were known to have consumed

any of the water; however, area

physicians and hospitals advised

that if anyone had consumed

those high levels of chromium,

the symptoms would be nausea,

diarrhea, and burning of the

mouth and throat. Fortunately,

the home economics teacher,

who first saw the discolored

water before school started,

immediately covered all water

fountains with towels so that

no one would drink the water.

Investigation disclosed

that chromium used in the

heating system boilers to inhibit

corrosion of metal parts entered

the potable water supply

system as a result of backflow

through leaking check valves

on the boiler feed lines.

Pesticide in

Drinking Water

Car Wash Water

in the Water Main

Street

A high school in New

Mexico, was closed for

several days in June 1984 when

a home economics teacher

noticed the water in the potable

system was yellow. City

chemists determined that

samples taken contained levels

of chromium as high as 700

parts per million, “astronomically higher than the accepted

levels of .05 parts per million.”

The head chemist said that it

was miraculous that no one was

seriously injured or killed by the

high levels of chromium. The

chemical was identified as

sodium dichromate, a toxic

form of chromium used in

heating system boilers to inhibit

corrosion of the metal parts.

A pesticide contaminated a

North Carolina water

system in April, 1986, prompting the town to warn residents

of 23 households not to drink

the water. The residents in the

affected area were supplied

drinking water from a tank

truck parked in the parking lot

of a downtown office building

until the condition could be

cleared up. Residents complained of foul smelling water

but there were no reports of

illness from ingesting the water

that had been contaminated

with a pesticide containing

chlordane and heptachlor.

Authorities stated that the

problem occurred when a water

main broke at the same time

that a pest control service was

filling a pesticide truck with

water. The reduction in pressure

caused the pesticide from inside

the tank to be sucked into the

building’s water main. The

pesticide contaminated the

potable water supply of the

office building and neighborhood area.

This car wash crossconnection and backpressure incident, which

occurred in February, 1979,

in the state of Washington,

resulted in backflow chemical

contamination of approximately

100 square blocks of water

mains. Prompt response by the

water department prevented a

potentially hazardous water

quality degradation problem

without a recorded case of

illness.

Numerous complaints of

grey-green and “slippery” water

were received by the water

department coming from the

same general area of town. A

sample brought to the water

department by a customer

confirmed the reported problem

and preliminary analysis

indicated contamination with

what appeared to be a detergent solution. While emergency

crews initiated flushing operations, further investigation

within the contaminated area

signaled the problem was

probably caused by a car wash,

Pump

Street

High School

Water cooler

Bubbler

Bubbler

Leaky check valves

High school boilers

Recommended installation

of backflow preventer

Toxic rust inhibitor and

defoamant containing

sodium dichromate

Recommended installation

of hose bibb vacuum breaker

backflow preventer

6 • CROSS-CONNECTION CONTROL MANUAL
Shipboard

raw water

pumping

system

To washrooms

To washrooms

Potable water supply

Cafeteria drinking fountains

and sanitation water

Reduced pressure principle backflow 

preventers should have been installed 

at dockside outlets and other locations

Potable supply hose

Wax injectors

To reclaim tanks

Scrubbers

Potable 

water supply

Rinse Rinse

Soap injectors

Hose connection

made here

Recommended

installation of

backflow preventer Reclaim tanks

Recirculating

pump

To restrooms

or laundry, based upon the

soapy nature of the contaminant. The source was quickly

narrowed down to a car wash

and the proprietor was extremely cooperative in admitting to the problem and

explaining how it had occurred.

The circumstances leading up

to the incident were as follows:

• On Saturday, February

10, 1979, a high pressure pump

broke down at the car wash.

This pump recycled reclaimed

wash and rinse water and

pumped it to the initial

scrubbers of the car wash. No

potable plumbing connection

is normally made to the car

wash’s scrubber system.

• After the pump broke

down, the car wash owner

was able to continue operation

by connecting a 2-inch hose

section temporarily between the

potable supply within the car

wash, and the scrubber cycle

piping.

• On Monday, February

12, 1979, the owner repaired

the high pressure pump and

resumed normal car wash

operations. The 2-inch hose

connection (cross-connection)

was not removed!

• Because of the crossconnection, the newly repaired

high pressure pump promptly

pumped a large quantity of

the reclaimed wash/rinse water

out of the car wash and into a

12-inch water main in the

street. This in turn was delivered to the many residences

and commercial establishments

connected to the water main.

Within 24 hours of the

incident, the owner of the car

wash had installed a 2-inch

reduced pressure principle

backflow preventer on his

water service and all car wash

establishments in Seattle that

used a wash water reclaim

system were notified of the

state requirement for backflow

prevention.

Shipyard

Backflow

Contamination

The cause of the problem

was a direct cross-connection

between the on-board salt

water fire protection water

system and the fresh water

connected to one of the ships at

the dock. While the shipyard

had been aware of the need

for backflow protection at the

dockside tie up area, the device

had not been delivered and

installed prior to the time of the

incident. As a result, the salt

water on-board fire protection

system, being at a greater

pressure than the potable

supply, forced the salt water,

through backpressure, into the

shipyard potable supply.

Fortunately, a small

demand for potable water at

the time of the incident

prevented widespread pollution

in the shipyard and the surrounding areas.

Water fountains at an East

Coast Shipyard were

posted “No Drinking” as

workers flushed the water lines

to eliminate raw river water

that had entered the shipyard

following contamination from

incorrectly connected water

lines between ships at the pier

and the shipyard. Some third

shift employees drank the

water before the pollution

was discovered and later

complained of stomach cramps

and diarrhea.

CHAPTER TWO • 7
Hexavalent

chromium

added to

chilled water

Main plant cooling line

Tempering

valve

Circulating

pumps

Hot water

heater

Laser

machine

Temporary

chiller

feed pump

To washrooms

Potable water supply

To plant bubblers

To ice making machines

To plant vending machines

Backpressure backflow path

Recommended installation of

backflow preventer

Chlordane in the

Water Main

I

n October, 1979, approximately three gallons of

chlordane, a highly toxic

insecticide, was sucked back

(back-siphoned) into the water

system of a residential area of

a good sized eastern city.

Residents complained that the

water “looked milky, felt greasy,

foamed and smelled,” and as

one woman put it, “It was

similar to a combination of

kerosene and Black Flag

pesticide.”

The problem developed

while water department

personnel were repairing a

water main. A professional

exterminator, meanwhile, was

treating a nearby home with

chlordane for termite elimination. The workman for the

exterminator company left one

Hexavalent

Chromium in

Drinking Water

I

n July, 1982, a well meaning

maintenance mechanic, in

attempting to correct a fogging

lens in an overcooled laser

machine, installed a tempering

valve in the laser cooling line,

and inadvertently set the stage

for a backpressure backflow

incident that resulted in

hexavalent chromium contaminating the potable water of a

large electronic manufacturing

company in Massachusetts

employing 9,000 people.

Quantities of 50 parts per

million hexavalent chromium

were found in the drinking

water which is sufficient to

cause severe vomiting, diarrhea,

end of a garden hose that was

connected to an outside hose

bibb tap in a barrel of diluted

pesticide. During the water

service interruption, the

chlordane solution was backsiphoned from the barrel

through the house and into the

water mains.

Following numerous

complaints, the water department undertook an extensive

program of flushing of the

water mains and hand delivered

letters telling residents to flush

their lines for four hours before

using the water. Until the water

lines were clear of the contaminant, water was hand-hauled

into homes, and people went

out of their homes for showers,

meals and every other activity

involving potable water.

Fortunately, due to the obvious

bad taste, odor and color of the

contaminated water, no one

consumed a sufficient quantity

to endanger health.

and intestinal sickness.

Maintenance crews working

during the plant shutdown

were able to eliminate the crossconnection and thoroughly

flush the potable water system,

thereby preventing a serious

health hazard from occurring.

The incident occurred as

follows:

• Laser machine lenses

were kept cool by circulating

chilled water that came from a

large refrigeration chiller. The

water used in the chiller was

treated with hexavalent

chromium, a chemical additive

used as an anticorrosive agent

and an algicide. As a result, the

chilled water presented a toxic,

non-potable substance unfit for

human consumption but very

CHLORDANE

Recommended installation of hose bibb

vacuum breaker backflow preventer

8 • CROSS-CONNECTION CONTROL MANUAL
Utility Heat exchanger

sink

Sink

Sink

Coffee

machine

Booster

pump

Recommended installation

of backflow preventers

Backpressure

backflow

Meter

Water

main

Water

fountatin

Roof mounted solar panels

Sink

Chemical

feeder

acceptable for industrial process

water. No health hazard was

present as long as the piping

was identified, kept separate

from potable drinking water

lines, and not cross-connected

to the potable water supply.

• A maintenance

mechanic correctly reasoned

that by adding a tempering

valve to the chilled water line,

he could heat up the water a bit

and eliminate fogging of the

laser lenses resulting from the

chilled water being too cold.

The problem with the installation of the tempering valve was

that a direct cross-connection

had been inadvertently made

between the toxic chilled water

and the potable drinking water

line!

• Periodic maintenance

to the chiller system was

performed in the summer,

requiring that an alternate

chiller feed pump be temporarily installed. This replacement pump had an outlet

pressure of 150 psi, and

promptly established an

imbalance of pressure at the

tempering valve, thereby overpressurizing the 60 psi, potable

supply. Backpressure backflow

resulted and pushed the toxic

chilled water from the water

heater and then into the plant’s

potable drinking water supply.

Yellowish green water started

pouring out of the drinking

fountains, the washroom, and

all potable outlets.

Employee Health

Problems due to

Cross-Connection

supply line! As the storage tank

pressure increased above the

supply pressure, as a result of

thermal expansion, the potential for backpressure backflow

was present. Normally, this

would not occur because a

boost pump in the supply line

would keep the supply pressure

to the storage tank always

greater than the highest tank

pressure. The addition of rust

inhibiting chemicals to this

tank greatly increased the

degree of hazard of the liquid.

Unfortunately, at the same time

that the fire took place, the

pressure in the water mains was

reduced to a dangerously low

pressure and the low pressure

cutoff switches simultaneously

shut off the storage tank

booster pumps. This combination allowed the boiler water,

together with its chemical

contaminants, the opportunity

to enter the potable water

supply within the building.

When normal pressure was

reestablished in the water

mains, the booster pumps

kicked in, and the contaminated water was delivered

throughout the building.

A cross-connection incident

occurring in a modern

seven-story office building

located in a large city in New

Hampshire, in March, 1980,

resulted in numerous cases of

nausea, diarrhea, loss of time

and employee complaints as to

the poor quality of the water.

On Saturday, March 1,

1980, a large fire occurred two

blocks away from a seven-story

office building in this large

New Hampshire city. On

Sunday, March 2, 1980, the

maintenance crew of the office

building arrived to perform the

weekly cleaning, and after

drinking the water from the

drinking fountains, and

sampling the coffee from the

coffee machines, noticed that

the water smelled rubbery and

had a strong bitter taste. Upon

notifying the Manchester Water

Company, water samples were

taken and preliminary analysis

disclosed that the contaminants

found were not the typical

contaminants associated with

fire line disturbances. Investigating teams suspected that

either the nearby fire could

have siphoned contaminants

from adjacent buildings into the

water mains, or the contamination could have been caused by

a plumbing deficiency occurring

within the seven story building

itself.

Water ph levels of the

building water indicated that

an injection of chemicals had

probably taken place within the

seven-story building. Tracing of

the water lines within the

building pinpointed a 10,000

gallon hot-water storage tank

that was used for heat storage

in the solar heating system. It

did not have any backflow

protection on the make-up

CHAPTER TWO • 9
Operating room

Air conditioning units

Glycol/water

pressurized

holding tank

Submerged inlet

cross-connection

Dialysis room

Recommneded installation

of backflow preventer Slightly

open

manual

Dialysis valve

filtration

unit

Intensive care Rest

room

Autopsy

Washroom

Laundry facility

Backpressure backflow

Main water

supply

Recommended installation

of backflow preventer

Boiler

room

Dialysis Machine

Contamination

potable supply line and fed

through a manually operated

control valve. With this valve

open, or partially open, potable

make-up water flowed slowly

into the glycol/water mixture in

the holding tank until it filled

to the point where the pressure

in the closed tank equaled the

pressure in the potable water

supply feed line. As long as the

potable feed line pressure was at

least equal to, or greater than,

the holding tank pressure, no

backflow could occur. The stage

was set for disaster, however.

It was theorized that

someone in the medical center

flushed a toilet or turned on a

faucet, which in turn dropped

the pressure in the potable

supply line to the air conditioning holding tank. Since the

manually operated fill valve was

partially open, this allowed the

glycol/water mixture to enter

the medical center potable

pipelines and flow into the

dialysis equipment. The dialysis

filtration system takes out trace

chemicals such as those used in

the city water treatment plant,

but the system could not

handle the heavy load of

chemicals that it was suddenly

subjected to.

The effect upon the dialysis

patients was dramatic: patients

became drowsy, confused and

fell unconscious, and were

promptly removed to intensive

care where blood samples were

taken. The blood samples

revealed a build-up of acid and

the medical director stated that,

“Something has happened in

dialysis.” Dialysis was repeated

on the patients a second and

third time.

Tests of the water supply to

the filtration system quickly

determined the presence of “an

undesirable chemical in the

water purification system.” The

partially open fill valve was

then found that it had permitted the glycol water mix to

drain from the air conditioning

holding tank into the medical

center’s potable supply lines

and then into the dialysis

filtration system equipment.

Creosote in the

Water Mains

10 • CROSS-CONNECTION CONTROL MANUAL

Ethylene glycol, an antifreeze additive to air

conditioning cooling tower

water, inadvertently entered the

potable water supply system in

a medical center in Illinois in

September, 1982, and two of

six dialysis patients succumbed

as a direct or indirect result of

the contamination.

The glycol was added to

the air conditioning water, and

the glycol/water mix was stored

in a holding tank that was an

integral part of the medical

center’s air conditioning cooling

system. Pressurized make-up

water to the holding tank was

supplied by a medical center

Creosote entered the water

distribution system of a

southeastern county water

authority in Georgia, in

November, 1984, as a result of

cross-connection between a

3⁄4-inch hose that was being

used as a priming line between

a fire service connection and the

suction side of a creosote pump.

The hose continually supplied

water to the pump to ensure

the pump was primed at all

times. However, while repairs

were being made to a private

fire hydrant, the creosote backsiphoned into the water mains

and contaminated a section of

the water distribution system.

Detailed investigation of

the cause of the incident

disclosed that the wood

preservative company, as part of

their operation, pumped

creosote from collective pits to

other parts of their operation.

The creosote pump would

automatically shut off when the

creosote in the pit was lowered

to a predetermined level. After

the creosote returned to a

higher level, the pump would

restart. This pump would lose

its prime quite often prior to

the pit refilling, and to prevent

the loss of prime, the wood

preservative company would

connect a hose from a 3⁄4-inch

hose bibb, located on the fire

service line, to the suction side

of the pump. The hose bibb

remained open at all times in an

effort to continuously keep the

pump primed.
Repairs were necessary to

one of the private fire hydrants

on the wood preservative

company property, necessitating

the shutting down of one of two

service lines and removal of the

damaged fire hydrant for repair.

Since the hydrant was at a

significantly lower level than

the creosote pit, the creosote

back-siphoned through a 3⁄4-

inch pump priming hose

connecting the creosote pit to

the fire service line.

After the repairs were

made to the hydrant, and the

water service restored, the

creosote, now in the fire lines,

was forced into the main water

distribution system.

Kool-Aid Laced

With Chlordane

CHAPTER TWO • 11

Street main

Street main

Creosote pump

Creosote

contaminated flow

Recommended installation

of backflow preventers

Private shut-off

Process

water

Recommended installation

of backflow preventers

I

n August, 1978, a professional exterminator was

treating a church located in a

small town in South Carolina,

for termite and pest control.

The highly toxic insecticide

chlordane was being mixed

with water in small buckets,

and garden hoses were left

submerged in the buckets while

the mixing was being accomplished. At the same time,

water department personnel

came by to disconnect the

parsonage’s water line from the

church to install a separate

water meter for the parsonage.

In the process, the water was

shut off in the area of the

church building. Since the

church was located on a steep

hill, and as the remaining water

in the lines was used by

residents in the area, the church

was among the first places to

experience a negative pressure.

The chlordane was quickly

siphoned into the water lines

within the church and became

mixed with the Kool-Aid being

prepared by women for the

vacation bible school. Approximately a dozen children and

three adults experienced

dizziness and nausea. Fortunately, none required hospitalization or medical attention.

Recommended installation

of hose bibb vacuum 

breaker backflow preventer
Chapter Three

A cross-connection1

 is the

link or channel connecting

a source of pollution with a

potable water supply. The

polluting substance, in most

cases a liquid, tends to enter the

potable supply if the net force

acting upon the liquid acts in

the direction of the potable

supply. Two factors are therefore

essential for backflow. First,

there must be a link between

the two systems. Second, the

resultant force must be toward

the potable supply.

An understanding of the

principles of backflow and

backsiphonage requires an

understanding of the terms

frequently used in their

discussion. Force, unless completely resisted, will produce

motion. Weight is a type of

force resulting from the earth’s

gravitational attraction.

Pressure (P) is a force-per-unit

area, such as pounds per square

inch (psi). Atmospheric pressure is

the pressure exerted by the

weight of the atmosphere above

the earth.

Pressure may be referred to

using an absolute scale, pounds

per square inch absolute (psia),

or gage scale, pounds per

square inch gage (psig).

Absolute pressure and gage

pressure are related. Absolute

pressure is equal to the gage

pressure plus the atmospheric

pressure. At sea level the

atmospheric pressure is 14.7

psia. Thus,

Pabsolute = Pgage + 14.7psi

or

Pgage = Pabsolute – 14.7 psi

In essence then, absolute

pressure is the total pressure.

Gage pressure is simply the

pressure read on a gage. If there

is no pressure on the gage other

than atmospheric, the gage

would read zero. Then the

absolute pressure would be

equal to 14.7 psi which is the

atmospheric pressure.

The term vacuum indicates

that the absolute pressure is less

than the atmospheric pressure

and that the gage pressure is

negative. A complete or total

vacuum would mean a pressure

of 0 psia or -14.7 psig. Since it

is impossible to produce a total

vacuum, the term vacuum, as

used in the text, will mean all

degrees of partial vacuum. In a

partial vacuum, the pressure

would range from slightly less

than 14.7 psia (0 psig) to

slightly greater than 0 psia

(-14.7 psig).

Backsiphonage1

 results in

fluid flow in an undesirable or

reverse direction. It is caused by

atmospheric pressure exerted on

a pollutant liquid forcing it

toward a potable water supply

system that is under a vacuum.

Backflow, although literally

meaning any type of reversed

flow, refers to the flow produced

by the differential pressure

existing between two systems

both of which are at pressures

greater than atmospheric.

Water Pressure

For an understanding of the

nature of pressure and its

relationship to water depth,

consider the pressure exerted on

the base of a cubic foot of water

at sea level. (See Fig. 1) The

average weight of a cubic foot

of water is 62.4 pounds per

square foot gage. The base may

be subdivided into 144-square

inches with each subdivision

being subjected to a pressure of

0.433 psig.

Suppose another cubic foot

of water were placed directly

on top of the first (See Fig. 2).

The pressure on the top surface

of the first cube which was

originally atmospheric, or

0 psig, would now be 0.433

psig as a result of the superimposed cubic foot of water.

The pressure of the base of

the first cube would also be

increased by the same amount

of 0.866 psig, or two times the

original pressure.

Theory of Backflow

and Backsiphonage

62.4#/ft3

0.433 psig

Sea level

12"

12" 12"

FIGURE 1.

Pressure exerted by 1 foot of

water at sea level.

1See formal definition in the glossary of

the appendix

12 • CROSS-CONNECTION CONTROL MANUAL
If this process were

repeated with a third cubic foot

of water, the pressures at the

base of each cube would be

1,299 psig, 0.866 psig, and

0.433 psig, respectively. It is

evident that pressure varies

with depth below a free water

surface; in general each foot of

elevation change, within a

liquid, changes the pressure by

an amount equal to the weightper-unit area of 1 foot of the

liquid. The rate of increase for

water is 0.433 psi per foot of

depth.

Frequently water pressure

is referred to using the terms

“pressure head” or just “head,”

and is expressed in units of feet

of water. One foot of head

would be equivalent to the

pressure produced at the base

of a column of water 1 foot in

depth. One foot of head or

1 foot of water is equal to 0.433

psig. One hundred feet of head

is equal to 43.3 psig.

Siphon Theory

Figure 3 depicts the atmospheric pressure on a water

surface at sea level. An open

tube is inserted vertically into

the water; atmospheric pressure, which is 14.7 psia, acts

equally on the surface of the

water within the tube and on

the outside of the tube.

level exactly balances the

weight of a column of water

33.9 feet in height. The

absolute pressure within the

column of water in Figure 4 at

a height of 11.5 feet is equal to

9.7 psia. This is a partial

vacuum with an equivalent

gage pressure of -5.0 psig.

As a practical example,

assume the water pressure at a

closed faucet on the top of a

100-foot high building to be 20

psig; the pressure on the

ground floor would then be

63.3 psig. If the pressure at the

ground were to drop suddenly

due to a heavy fire demand in

the area to 33.3 psig, the

pressure at the top would be

reduced to -10 psig. If the

building water system were

airtight, the water would

remain at the level of the faucet

because of the partial vacuum

created by the drop in pressure.

If the faucet were opened,

however, the vacuum would be

broken and the water level

would drop to a height of 77

feet above the ground. Thus,

the atmosphere was supporting

a column of water 23 feet high.

Figure 5 is a diagram of an

inverted U-tube that has been

filled with water and placed in

two open containers at sea level.

If the open containers are

placed so that the liquid levels

in each container are at the

same height, a static state will

exist; and the pressure at any

specified level in either leg of

the U-tube will be the same.

The equilibrium condition

is altered by raising one of the

containers so that the liquid

level in one container is 5 feet

If, as shown in Figure 4,

the tube is slightly capped and

a vacuum pump is used to

evacuate all the air from the

sealed tube, a vacuum with a

pressure of 0 psia is created

within the tube. Because the

pressure at any point in a static

fluid is dependent upon the

height of that point above a

reference line, such as sea level,

it follows that the pressure

within the tube at sea level

must still be 14.7 psia. This is

equivalent to the pressure at the

base of a column of water 33.9

feet high and with the column

open at the base, water would

rise to fill the column to a depth

of 33.9 feet. In other words, the

weight of the atmosphere at sea

0.433 psig

24"

0.866 psig Sea Level

14.7

14.7 psia psia

sea level

FIGURE 2.

Pressure exerted by 2 feet of

water at sea level.

FIGURE 3.

Pressure on the free surface of a

liquid at sea level.

FIGURE 4.

Effect of evacuating air from a

column.

FIGURE 5.

Pressure relationships in a

continuous fluid system at the

same elevation.

1See formal definition in the glossary of

the appendix

14.7

psia

9.7

psia

14.7 psia or

0.0 psig

or -5.0 psig

0.0

psia

or

-14.7

psig

Vacuum pump

“Zero” Absolute

Pressure

Sea level 39.9' 11.5'

14.7

psia

14.7

psia

4.7 psia

10.3 psia

23'

10'

CHAPTER THREE • 13
above the level of the other. (See

Fig. 6.) Since both containers

are open to the atmosphere, the

pressure on the liquid surfaces

in each container will remain at

14.7 psia.

If it is assumed that a static

state exists, momentarily,

within the system shown in

Figure 6, the pressure in the left

tube at any height above the

free surface in the left container

can be calculated. The pressure

at the corresponding level in the

right tube above the free surface

in the right container may also

be calculated.

As shown in Figure 6, the

pressure at all levels in the left

tube would be less than at

corresponding levels in the right

tube. In this case, a static

condition cannot exist because

fluid will flow from the higher

pressure to the lower pressure;

the flow would be from the

right tank to the left tank. This

arrangement will be recognized

as a siphon. The crest of a

siphon cannot be higher than

33.9 feet above the upper liquid

level, since atmosphere cannot

support a column of water

greater in height than 33.9 feet.

Figure 7 illustrates how

this siphon principle can be

hazardous in a plumbing

system. If the supply valve is

closed, the pressure in the line

supplying the faucet is less than

the pressure in the supply line

to the bathtub. Flow will occur,

therefore, through siphonage,

from the bathtub to the open

faucet.

shown that as a fluid accelerates, as shown in Figure 8, the

pressure is reduced. As water

flows through a constriction

such as a converging section of

pipe, the velocity of the water

increases; as a result, the

pressure is reduced. Under such

conditions, negative pressures

may be developed in a pipe.

The simple aspirator is based

upon this principle. If this

point of reduced pressure is

linked to a source of pollution,

backsiphonage of the pollutant

can occur.

flow from the source of pollution would occur when pressure

on the suction side of the pump

is less than pressure of the

pollution source; but this is

backflow, which will be discussed

below.

The preceding discussion

has described some of the

means by which negative

pressures may be created and

which frequently occur to

produce backsiphonage. In

addition to the negative

pressure or reversed force

necessary to cause

backsiphonage and backflow,

there must also be the crossconnection or connecting link

between the potable water

supply and the source of

pollution. Two basic types of

connections may be created in

piping systems. These are the

solid pipe with valved connection and the submerged inlet.

14 • CROSS-CONNECTION CONTROL MANUAL

14.7

psia

14.7

psia

10.3 psia 10'

8.2 psia15'

5'

FIGURE 6.

Pressure relationships in a

continuous fluid system at

different elevations.

Valve open

Closed supply

Valve open

Submerged inlet

FIGURE 7.

Backsiphonage in a plumbing

system.

The siphon actions cited

have been produced by reduced

pressures resulting from a

difference in the water levels at

two separated points within a

continuous fluid system.

Reduced pressure may also

be created within a fluid system

as a result of fluid motion. One

of the basic principles of fluid

mechanics is the principle of

conservation of energy. Based

upon this principle, it may be

+30 psig +30 psig -10 psig

FIGURE 8.

Negative pressure created by

constricted flow.

FIGURE 9.

Dynamically reduced pipe

pressures.

Booster pump

From pollution To fixture

source

+50 psig

-10

psig

One of the common

occurrences of dynamically

reduced pipe pressures is found

on the suction side of a pump.

In many cases similar to the one

illustrated in Figure 9, the line

supplying the booster pump is

undersized or does not have

sufficient pressure to deliver

water at the rate at which the

pump normally operates. The

rate of flow in the pipe may be

increased by a further reduction

in pressure at the pump intake.

This often results in the creation

of negative pressure at the

pump intake. This often results

in the creation of negative

pressure. This negative pressure

may become low enough in

some cases to cause vaporization

of the water in the line. Actually, in the illustration shown,
Figures 10 and 11 illustrate

solid connections. This type of

connection is often installed

where it is necessary to supply

an auxiliary piping system from

the potable source. It is a direct

connection of one pipe to

another pipe or receptacle.

Solid pipe connections are

often made to continuous or

intermittent waste lines where

it is assumed that the flow will

be in one direction only. An

example of this would be used

cooling water from a water

jacket or condenser as shown in

Figure 11. This type of connection is usually detectable but

creating a concern on the part

of the installer about the

possibility of reversed flow is

often more difficult. Upon

questioning, however, many

installers will agree that the

solid connection was made

because the sewer is occasionally subjected to backpressure.

Submerged inlets are found

on many common plumbing

fixtures and are sometimes

necessary features of the fixtures

if they are to function properly.

Examples of this type of design

are siphon-jet urinals or water

closets, flushing rim slop sinks,

and dental cuspidors. Oldstyle

bathtubs and lavatories had

supply inlets below the flood

level rims, but modern sanitary

design has minimized or

eliminated this hazard in new

fixtures. Chemical and industrial process vats sometimes

have submerged inlets where

the water pressure is used as an

aid in diffusion, dispersion and

agitation of the vat contents.

Even though the supply pipe

may come from the floor above

the vat, backsiphonage can

occur as it has been shown that

the siphon action can raise a

liquid such as water almost 34

feet. Some submerged inlets

difficult to control are those

which are not apparent until a

significant change in water level

occurs or where a supply may

be conveniently extended below

the liquid surface by means of a

hose or auxiliary piping. A

submerged inlet may be created

in numerous ways, and its

detection in some of these

subtle forms may be 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-connection,

and the cause of the negative

pressure.

Backflow

Backflow1, as described in this

manual, refers to reversed flow

due to backpressure other than

siphonic action. Any interconnected fluid systems in which

the pressure of one exceeds the

pressure of the other may have

flow from one to the other as a

result of the pressure differential. The flow will occur from

the zone of higher pressure to

the zone of lower pressure. This

type of backflow is of concern in

buildings where two or more

piping systems are maintained.

The potable water supply is

usually under pressure directly

from the city water main.

Occasionally, a booster pump is

used. The auxiliary system is

often pressurized by a centrifical

pump, although backpressure

may be caused by gas or steam

pressure from a boiler. A

reversal in differential pressure

may occur when pressure in the

potable system drops, for some

reason, to a pressure lower than

that in the system to which the

potable water is 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.

CHAPTER THREE • 15

FIGURE 11

Valved connection between

potable water and sanitary sewer.

City supply

Sanitary sewer

Condenser

FIGURE 10.

Valved connections between

potable water and nonpotable

fluid.

Non potable Potable

1See formal definition in the glossary of

the appendix
Chapter Four

A wide choice of devices

exists that can be used to

prevent backsiphonage and

backpressure from adding

contaminated fluids or gases

into a potable water supply

system. Generally, the selection

of the proper device to use is

based upon the degree of hazard

posed by the cross-connection.

Additional considerations are

based upon piping size, location,

and the potential need to

periodically test the devices to

insure proper operation.

There are six basic types of

devices that can be used to

correct cross-connections: air

gaps, barometric loops, vacuum

breakers—both atmospheric

and pressure type, double check

with intermediate atmospheric

vent, double check valve

assemblies, and reduced pressure

principle devices. In general, all

manufacturers of these devices,

with the exception of the

barometric loop, produce them

to one or more of three basic

standards, thus insuring the

public that dependable devices

are being utilized and marketed.

The major standards in the

industry are: American Society

of Sanitary Engineers ASSE),

American Water Works Association (AWWA), and the University of California Foundation for

Cross-Connection Control and

Hydraulic Research.

Air Gap

Air gaps are non-mechanical

backflow preventers that are

very effective devices to be used

where either backsiphonage or

backpressure conditions may

exist. Their use is as old as

piping and plumbing itself, but

only relatively recently have

standards been issued that

standardize their design. In

general, the air gap must be

twice the supply pipe diameter

but never less than one inch.

See Figure 12.

(2) The air gap may be easily

defeated in the event that the

“2D” requirement was purposely

or inadvertently compromised.

Excessive splash may be encountered in the event that higher

than anticipated pressures or

flows occur. The splash may be a

cosmetic or true potential

hazard—the simple solution

being to reduce the “2D”

dimension by thrusting the

supply pipe into the receiving

funnel. By so doing, the air gap

is defeated.

(3) At an air gap, we expose the

water to the surrounding air

with its inherent bacteria, dust

particles, and other airborne

pollutants or contaminants. In

addition, the aspiration effect of

the flowing water can drag down

surrounding pollutants into the

reservoir or holding tank.

(4) Free chlorine can come out of

treated water as a result of the air

gap and the resulting splash and

churning effect as the water

enters the holding tanks. This

reduces the ability of the water

to withstand bacteria contamination during long term storage.

(5) For the above reasons, air

gaps must be inspected as

frequently as mechanical

backflow preventers. They are

not exempt from an in-depth

cross-connection control program requiring periodic inspection of all backflow devices.

Air gaps may be fabricated

from commercially available

plumbing components or

purchased as separate units and

integrated into plumbing and

piping systems. An example of

the use of an air gap is shown in

Figure 13.

16 • CROSS-CONNECTION CONTROL MANUAL

Methods and Devices

for the Prevention of

Backflow and

Back-Siphonage

An air gap, although an

extremely effective backflow

preventer when used to prevent

backsiphonage and backpressure conditions, does interrupt

the piping flow with corresponding loss of pressure for

subsequent use. Consequently,

air gaps are primarily used at

end of the line service where

reservoirs or storage tanks are

desired. When contemplating

the use of an air gap, some

other considerations are:

(1) In a continuous piping

system, each air gap requires

the added expense of reservoirs

and secondary pumping

systems.

FIGURE 12.

Air gap.

Diameter

“D”

“2D”
Barometric Loop

The barometric loop consists of

a continuous section of supply

piping that abruptly rises to a

height of approximately 35 feet

and then returns back down to

the originating level. It is a loop

in the piping system that

effectively protects against

backsiphonage. It may not be

used to protect against backpressure.

Its operation, in the

protection against backsiphonage, is based upon the

principle that a water column,

at sea level pressure, will not

rise above 33.9 feet (Ref.

Chapter 3, Fig. 4 Page 13).

In general, barometric

loops are locally fabricated, and

are 35 feet high.

Atmospheric Vacuum

Breaker

These devices are among the

simplest and least expensive

mechanical types of backflow

preventers and, when installed

properly, can provide excellent

protection against backsiphonage. They must not be

utilized to protect against

backpressure conditions.

Construction consists usually of

a polyethylene float which is

free to travel on a shaft and seal

in the uppermost position

against atmosphere with an

elastomeric disc. Water flow

lifts the float, which then causes

the disc to seal. Water pressure

keeps the float in the upward

sealed position. Termination of

the water supply will cause the

disc to drop down venting the

unit to atmosphere and thereby

opening downstream piping to

atmospheric pressure, thus

preventing backsiphonage.

Figure 15 shows a typical

atmospheric breaker.

In general, these devices

are available in 1⁄2-inch through

3-inch size and must be

installed vertically, must not

have shutoffs downstream,

and must be installed at least

6-inches higher than the final

outlet. They cannot be tested

once they are installed in the

plumbing system, but are, for

the most part, dependable,

trouble-free devices for

backsiphonage protection.

Figure 16 shows the

generally accepted installation

requirements—note that no

shutoff valve is downstream

of the device that would

otherwise keep the atmospheric

vacuum breaker under constant

pressure.

Figure 17 shows a typical

installation of an atmospheric

vacuum breaker in a plumbing

supply system.

CHAPTER FOUR • 17

FIGURE 13.

Air gap in a piping system.

Supply piping

Tank or reservoir

FIGURE 14.

Barometric loop.

FIGURE 15.

Atmospheric vacuum breaker.

35'

FIGURE 16.

Atmospheric vacuum breaker

typical installation.

FIGURE 17.

Atmospheric vacuum breaker in

plumbing supply system.

Flow condition

Seal

Non flow condition

Not less than 6"
Hose Bibb

Vacuum Breakers

These small devices are a

specialized application of the

atmospheric vacuum breaker.

They are generally attached to

sill cocks and in turn are

connected to hose supplied

outlets such as garden hoses,

slop sink hoses, spray outlets,

etc. They consist of a spring

loaded check valve that seals

against an atmospheric outlet

when water supply pressure is

turned on. Typical construction

is shown in Figure 18.

When the water supply is

turned off, the device vents to

atmosphere, thus protecting

against backsiphonage conditions. They should not be used

as backpressure devices. Manual

drain options are available,

together with tamper-proof

versions. A typical installation is

shown in Figure 19.

Pressure

Vacuum Breakers

This device is an outgrowth of

the atmospheric vacuum

breaker and evolved in response

to a need to have an atmospheric vacuum breaker that could be

utilized under constant pressure

and that could be tested in line.

A spring on top of the disc and

float assembly, two added gate

valves, test cocks, and an

additional first check, provided

the answer to achieve this

device. See Figure 20.

These units are available in

the general configurations as

shown in Figure 20 in sizes

1⁄2-inch through 10-inch and

have broad usage in the

agriculture and irrigation

market. Typical agricultural and

industrial applications are

shown in Figure 21.

Again, these devices may

be used under constant pressure

but do not protect against

backpressure conditions. As a

result, installation must be at

least 6- to 12-inches higher

than the existing outlet.

A spill resistant pressure

vacuum breaker (SVB) is

available that is a modification

to the standard pressure

vacuum breaker but specifically

designed to minimize water

spillage. Installation and

hydraulic requirements are

similar to the standard pressure

vacuum breaker and the

devices are recommended for

internal use.

18 • CROSS-CONNECTION CONTROL MANUAL

Hose bibb vacuum breaker

3⁄4 inch thru 2 inches

21⁄2 inches thru 10 inches

Spring

Gate Valve

Gate Valve

Test cock

Test cock

First check valve

FIGURE 18.

Hose bibb vacuum breaker.

FIGURE 19.

Typical installation of hose bibb

vacuum breaker.

FIGURE 20.

Pressure vacuum breaker
Double Check with

Intermediate

Atmospheric Vent

The need to provide a compact

device in 1⁄2-inch and 3⁄4-inch

pipe sizes that protects against

moderate hazards, is capable of

being used under constant

pressure and that protects

against backpressure, resulted

in this unique backflow

preventer. Construction is

basically a double check valve

having an atmospheric vent

located between the two checks

(See Figure 22).

Line pressure keeps the

vent closed, but zero supply

pressure or backsiphonage will

open the inner chamber to

atmosphere. With this device,

extra protection is obtained

through the atmospheric vent

capability. Figure 23 shows a

typical use of the device on a

residential boiler supply line.

Double Check Valve

A double check valve is

essentially two single check

valves coupled within one body

and furnished with test cocks

and two tightly closing gate

valves (See Figure 24).

The test capability feature

gives this device a big advantage over the use of two

independent check valves in

that it can be readily tested to

determine if either or both

check valves are inoperative

or fouled by debris. Each check

is spring loaded closed and

requires approximately a pound

of pressure to open.

This spring loading

provides the ability to “bite”

through small debris and still

seal—a protection feature not

prevalent in unloaded swing

check valves. Figure 24 shows a

cross section of double check

valve complete with test cocks.

Double checks are commonly

used to protect against low to

medium hazard installations

such as food processing steam

kettles and apartment projects.

They may be used under

continuous pressure and protect

against both backsiphonage and

backpressure conditions.

CHAPTER FOUR • 19

Vent

1st check 2nd check

Drain

Air gap

Automatic feed valve Supply

Return

Boiler

FIGURE 21.

Typical agricultural and

industrial application of

pressure vacuum breaker.

FIGURE 22.

Double check valve with

atmospheric vent.

FIGURE 23.

Typical residential use of double

check with atmospheric vent.

FIGURE 24.

Double check valve.

At least 6" Process tanks

12" minimum above

the highest outlet

Hose bibb
Double Check Detector

Check

This device is an outgrowth of

the double check valve and is

primarily utilized in fire line

installations. Its purpose is to

protect the potable supply line

from possible contamination or

pollution from fire line chemical

additives, booster pump fire

line backpressure, stagnant

“black water” that sits in fire

lines over extended periods of

time, the addition of “raw”

water through outside fire

pumper connections (Siamese

outlets), and the detection of

any water movement in the fire

line water due to fire line

leakage or deliberate water

theft. It consists of two, spring

loaded check valves, a bypass

assembly with water meter and

double check valve, and two

tightly closing gate valves. See

Figure 25. The addition of test

cocks makes the device testable

to insure proper operation of

both the primary checks and

the bypass check valve. In the

event of very low fire line water

usage, (theft of water) the low

pressure drop inherent in the

bypass system permits the low

flow of water to be metered

through the bypass system. In a

high flow demand, associated

with deluge fire capability, the

main check valves open,

permitting high volume, low

restricted flow, through the two

large spring loaded check

valves.

Residential Dual Check

The need to furnish reliable and

inexpensive backsiphonage and

backpressure protection for

individual residences resulted in

the debut of the residential dual

check. Protection of the main

potable supply from household

hazards such as home photograph chemicals, toxic insect

and garden sprays, termite

control pesticides used by

exterminators, etc., reinforced,

a true need for such a device.

Figure 26 shows a cutaway of

the device.

It is sized for 1⁄2-, 3⁄4-, and

1-inch service lines and is

installed immediately downstream of the water meter. The

use of plastic check modules

and elimination of test cocks

and gate valves keeps the cost

reasonable while providing

good, dependable protection.

Typical installations are shown

in Figures 27 and 28.

20 • CROSS-CONNECTION CONTROL MANUAL

Residential

dual check

Water meter

Water meter

11⁄4" meter thread female inlet with

1" NPT thread female union outlet

FIGURE 25.

Double check detector check.

FIGURE 26.

Residential dual check.

FIGURE 27.

Residential installation.

FIGURE 28.

Copper horn.
100 psi 95 psi

Out 47 psi

50 psi

Supply 60 psi

94 psi

Reduced Pressure

Principle Backflow

Preventer

Maximum protection is

achieved against backsiphonage

and backpressure conditions

utilizing reduced pressure

principle backflow preventers.

These devices are essentially

modified double check valves

with an atmospheric vent

capability placed between the

two checks and designed such

that this “zone” between the

two checks is always kept at

least two pounds less than the

supply pressure. With this

design criteria, the reduced

pressure principle backflow

preventer can provide protection against backsiphonage and

backpressure when both the

first and second checks become

fouled. They can be used under

constant pressure and at high

hazard installations. They are

furnished with test cocks and

gate valves to enable testing

and are available in sizes 3⁄4-inch

through 10 inch.

Figure 29A shows typical

devices representative of 3⁄4-inch

through 2-inch size and Figure

29B shows typical devices

representative of 21⁄2-inch

through 10-inch sizes.

CHAPTER FOUR • 21

FIGURE 29A.

Reduced pressure zone backflow

preventer (3⁄4-inch thru 2-inches).

FIGURE 29B.

Reduced pressure zone backflow

preventer (21⁄2-inches thru 10-

inches).

Relief valve (rotated 90 ̊ for clarity)

Reduced pressure zone

1st check valve 2nd check valve

94 psi 93 psi 100 psi
22 • CROSS-CONNECTION CONTROL MANUAL

The principles of operation

of a reduced pressure principle

backflow preventer are as

follows:

Flow from the left enters

the central chamber against the

pressure exerted by the loaded

check valve 1. The supply

pressure is reduced thereupon

by a predetermined amount.

The pressure in the central

chamber is maintained lower

than the incoming supply

pressure through the operation

of the relief valve 3, which

discharges to the atmosphere

whenever the central chamber

pressure approaches within a

few pounds of the inlet pressure. Check valve 2 is lightly

loaded to open with a pressure

drop of 1 psi in the direction of

flow and is independent of the

pressure required to open the

relief valve. In the event that

the pressure increases downstream from the device, tending

to reverse the direction of flow,

check valve 2 closes, preventing

backflow. Because all valves

may leak as a result of wear or

obstruction, the protection

provided by the check valves is

not considered sufficient. If

some obstruction prevents

check valve 2 from closing

tightly, the leakage back into

the central chamber would

increase the pressure in this

zone, the relief valve would

open, and flow would be

discharged to the atmosphere.

When the supply pressure

drops to the minimum differential required to operate the

relief valve, the pressure in the

central chamber should be

atmospheric. If the inlet

pressure should become less

than atmospheric pressure,

relief valve 3 should remain

fully open to the atmosphere to

discharge any water which may

be caused to backflow as a

result of backpressure and

leakage of check valve 2.

Malfunctioning of one or

both of the check valves or relief

valve should always be indicated by a discharge of water

from the relief port. Under no

circumstances should plugging

of the relief port be permitted

because the device depends

upon an open port for safe

operation. The pressure loss

through the device may be

expected to average between

10 and 20 psi within the

normal range of operation,

depending upon the size and

flow rate of the device.

Reduced pressure principle

backflow preventers are

commonly installed on high

hazard installations such as

plating plants, where they

would protect against primarily

backsiphonage potential, car

washes where they would

protect against backpressure

conditions, and funeral parlors,

hospital autopsy rooms, etc.

The reduced pressure principle

backflow preventer forms the

backbone of cross-connection

control programs. Since it is

utilized to protect against high

hazard installations, and since

high hazard installations are the

first consideration in protecting

public health and safety, these

devices are installed in large

quantities over a broad range of

plumbing and water works

installations. Figures 31 and 32

show typical installations of

these devices on high hazard

installations.

Direction

of flow

1 2

3

Reversed direction 

of flow

Reduced pressure principle backflow preventer Water main

Meter

Main

Reduced pressure principle

backflow preventer

FIGURE 30.

Reduced pressure zone backflow

preventer — principle of operation.

FIGURE 31.

Plating plant installation.

FIGURE 32.

Car wash installation.
CHAPTER ONE • 23

FIGURE 33.

Typical bypass configuration

reduced pressure principle

devices

FIGURE 34.

Typical installation reduced

pressure principle device

horizontal illustration.

Typical fire line installation double

check valve vertical installation.

FIGURE 35.

Typical installation reduced

pressure principle device vertical

illustration.

Reduced pressure

principle device

Water meter

Note: Device to be set 12" minimum from wall.

Air gap

Drain 12" min. 30" max.

Reduced pressure

principle device

Water meter

Air gap

Elbow

Drain

Note: (1) Refer to manufacturers installation data for vertical mount.

(2) Unit to be set at a height to permit ready access for testing and service.

(3) Vertical installation only to be used if horizontal installation cannot be achieved.

Reduced pressure principle device

Note: Devices to be set a min. of 12" and a max. of 30" from the floor and 12" from any wall.

Reduced pressure

principle device

Air gap

Drain

Air gap

Drain

Double check

valve

Alarm check

Grade

OS&Y gate valve

Fire pipe

Siamese

check

Siamese

fitting
24 • CROSS-CONNECTION CONTROL MANUAL

FIGURE 36.

Typical installation double check

valve horizontal and vertical

installation.

FIGURE 37.

Typical installation residential dual

check with straight set and

copperhorn.

Note: Vertical installation only to be used if horizontal 

installation cannot be achieved.

Double check valve

Double check valve

(unit to be set at a height

that permits ready access

for testing and service)

Water meter

Copperhorn with 

water meter

12" min. 30" max.

Residential dual

check valve

Residential

dual check

3⁄4" ball valve

3⁄4" ball valve

3⁄4" K-copper

Water meter

Copperhorn with 

water meter
Chapter Five

Prior to initiating a test of

any backflow device, it is

recommended that the following procedures be followed:

1. Permission be obtained from

the owner, or his representative,

to shut down the water supply.

This is necessary to insure that

since all testing is accomplished

under no-flow conditions, the

owner is aware that his water

supply will be temporarily shut

off while the testing is being

performed. Some commercial

and industrial operations

require constant and uninterrupted water supplies for

cooling, boiler feed, seal pump

water, etc. and water service

interruption cannot be tolerated. The water supply to

hospitals and continuous

process industries cannot be

shut off without planned and

coordinated shut downs. The

request to shut down the water

supply is therefore a necessary

prerequisite to protect the

customer as well as limit the

liability of the tester.

Concurrent with the

request for permission to shut

off the water, it is advisable to

point out to the owner, or his

representative, that while the

water is shut off during the test

period, any inadvertent use of

water within the building will

reduce the water pressure to

zero. Backsiphonage could

result if unprotected crossconnections existed which

would contaminate the building

water supply system. In order

to address this situation, it is

recommended that the owner

caution the inhabitants of the

building not to use the water

until the backflow test is

completed and the water

pressure restored. Additional

options available to the building

owner would be the installation

of two backflow devices in

parallel that would enable a

protected bypass flow around

the device to be tested. Also, if

all water outlets are protected

within the building with

“fixture outlet protection”

backflow devices, crossconnections would not create a

problem in the event of

potential backsiphonage

conditions occurring while

devices are tested, or for any

other reason.

2. Determine the type of device

to be tested i.e., double check

valve or reduced pressure

principle device.

3. Determine the flow direction. (Reference directional flow

arrows or wording provided by

the manufacturer on the

device.)

4. Number the test cocks, bleed

them of potential debris, and

assemble appropriate test cock

adapters and bushings that may

be required.

5. Shut off the downstream

(number 2) shut-off valve. (Ref.

Item (1) above.)

6. Wait several moments prior

to hooking up the test kit hoses

when testing a reduced pressure

principle device. If water exits

the relief valve, in all likelihood,

the first check valve is fouled

and it is impractical to proceed

with the testing until the valve

is serviced. This waiting period

is not necessary when testing

double check valves.

7. Hook up the test kit hoses in

the manner appropriate to the

device being tested and the

specific test being performed.

Test personnel are cautioned to be aware and follow

local municipal, county, and

state testing requirements and

guidelines as may be dictated

by local authority. The following test procedures are guidelines for standard, generally

acceptable test procedures

but may be amended, superceded, or modified by local

jurisdiction.

CHAPTER FIVE • 25

Testing Procedures

for Backflow

Preventers
Test Equipment

number 1 shut-off valve

open) bleed test cocks

number 1 and number 2.

2. Hook up the high pressure

hose to number 1 test cock

and the low pressure hose

to number 2 test cock.

3. Bleed the high pressure

hose, and low pressure

hose, in that order, and

close the test kit needle

valves slowly.

4. Record the differential

pressure on the gauge. A

reading of 1 psid is

acceptable to insure a tight

check valve.

Test 2 Test the air inlet valve

for a breakaway of 1 psi.

1. Connect the high pressure

hose to test cock number 2,

and bleed the high pressure

hose.

2. Shut off number 1 shut-off

valve.

3. Slowly open the bleed valve

of the test kit, and observe

and record the psi when

the air inlet poppet opens.

This should be a minimum

of 1 psi. Restore the valve

to normal service.

Method 2

Using a water column sight

tube and 90 degree elbow

fitting with bleed needle

Test 1 Test the internal check

valve for tightness of 1 psid in

the direction of flow.

1. Assemble sight tube to test

cock number 1. Open test

cock and fill the tube to a

minimum of 36-inches of

water height.

2. Close number 1 shut-off

valve.

3. Open test cock number 2.

The air inlet valve should

open and discharge water

through number 2 test

cock.

4. Open number 1 test cock.

The sight tube level of

water should drop slowly

until it stabilizes. This

point should be a minimum of 28-inches of water

column which equals 1 psi.

Test 2 Test the air inlet valve

for a breakaway of 1 psi.

1. Assemble sight tube to

test cock number 2. Open

test cock number 2 and fill

the tube to a minimum of

36-inches of water height.

2. Close number 1 shut-off

valve.

3. Bleed water slowly from

the number 2 test cock

bleed needle and observe

the water column height as

it drops.

4. At the point when the air

inlet valve pops open,

record the height of the

water column. This point

should be a minimum of

28-inches of water column

which equals 1psi.

Restore the valve to normal

service.

Reduced Pressure

Principle Backflow

Preventer

(Figure 39)

Field testing of a reduced

pressure principle backflow

preventer is accomplished

utilizing a differential pressure

gauge. The device is tested for

three optional characteristics:

i.e., (1) the first check valve is

tight and maintains a minimum

of 5 psi differential pressure,

(2) the second check valve is

tight against backpressure and

(3) the relief valve opens at a

minimum of 2 psi below inlet

supply pressure. Testing is

performed as follows:

Step 1 Test to insure that the

first check valve is tight and

maintains a minimum pressure

of 5 psi differential pressure.

1. Verify that number 1 shutoff valve is open. Close

number 2 shut-off valve.

If there is no drainage

from the relief valve it is

assumed that the first

check is tight.

2. Close all test kit valves.

3. Connect the high pressure

hose to test cock number 2.

4. Connect the low pressure

hose to test cock number 3.

5. Open test cocks number 2

and number 3.

6. Open high side bleed

needle valve on test kit

bleeding the air from the

high hose. Close the high

side bleed needle valve.

7. Open the low side bleed

needle valve on test kit

bleeding air from the low

hose. Close the low side

bleed needle valve. Record

the differential gauge

pressure. It should be a

minimum of 5 psid.

For field testing of reduced

pressure principle backflow

preventers and double check

valve assemblies, a differential

pressure test gauge is utilized

having a 0 to 15 psi range and

a working pressure of 500 psi.

Appropriate length of hoses

with necessary fittings accompany the test gauge. Several

manufactured test kits are

commercially available that

incorporate the differential

gauge, hoses, and fittings and

are packaged for ease of

portability and come with

protective enclosures or straps

for hanging. Calibrated water

columns are commercially

available that are portable and

come with carrying cases.

It is important that all test

equipment be periodically

checked for calibration.

Pressure Vacuum

Breaker

(Figure 38)

Field testing of a pressure

vacuum breaker involves testing

both the internal spring loaded

soft seated check valve as well

as testing the spring loaded air

inlet valve. The testing must be

performed with the device

pressurized and the air inlet

closed. The number 2 shut-off

valve must also be closed and

the air inlet valve canopy

removed.

Method 1

Using a differential pressure

gauge

Test 1 Test the internal check

valve for tightness of 1 psid in

the direction of flow.

1. With the valve body under

pressure, (number 2 shutoff valve closed and

No. 2 shut off valve

Test cock

No. 1

Check valve

Loaded air inlet valve

Air inlet valve canopy

No. 1 shut off valve

Test cock

No. 2

FIGURE 38.

26 • CROSS-CONNECTION CONTROL MANUAL
Step 2 Test to insure that the

second check is tight against

backpressure. (Figure 40)

1. Leaving the hoses hooked

up as in the conclusion of

Step 1 above, connect the

bypass hose to test cock

number 4.

2. Open test cock number 4,

the high control needle

valve and the bypass hose

control needle valve on the

test kit. (This supplies high

pressure water downstream

of check valve number 2.)

If the differential pressure

gauge falls off and water

comes out of the relief

valve, the second check is

recorded as leaking. If the

differential pressure gauge

remains steady, and no

water comes out of the

relief valve, the second

check valve is considered

tight

3. To check the tightness of

number 2 shut-off valve,

leave the hoses hooked up

the same as at the conclusion of Step 2 above, and

then close test cock

number 2. This stops the

supply of any high pressure

water downstream of check

valve number 2. If the

differential pressure gauge

reading holds steady, the

number 2 shut-off valve is

recorded as being tight. If

the differential pressure

gauge drops to zero, the

number 2 shut-off valve is

recorded as leaking.

With a leaking number 2

shut-off valve, the device is, in

most cases, in a flow condition

and the previous readings taken

are invalid. Unless a non-flow

condition can be achieved,

either through the operation of

an additional shut-off downstream, or the use of a temporary compensating bypass hose,

accurate test results will not be

achieved.

Step 3 To check that the relief

valve opens at a minimum

pressure of 2 psi below inlet

pressure.

1. With the hoses hooked up

the same as at the conclusion of Step #2 (3) above,

slowly open up the low

control needle valve on the

test kit and record the

differential pressure gauge

reading at the point when

the water initially starts to

drip from the relief valve

opening. This pressure

reading should not be

below 2 psid.

This completes the

standard field test for a reduced

pressure principle backflow

preventer. Before removal of the

test equipment, the tester

should insure that he opens

number 2 shut-off valve

thereby reestablishing flow.

Also, the test kit should be

thoroughly drained of all water

to prevent freezing by opening

all control needle valves and

bleed needle valves.

All test data should be

recorded on appropriate forms.

(Ref: sample Page 45)

Note: The steps outlined above may

vary in sequence depending upon local

regulations and/or preferences.

FIGURE 39.

FIGURE 40.

Temporary

bypass hose Tee

Bleed needle valves

Control

needle

valves

High side

hose

Low side

hose

Bypass hose

Test cock No. 1

Test cock No. 2

Check valve No. 1

Test cock No. 3

Check valve No. 2

Test cock No. 4

No. 1 shut off valveNo. 2 shut off valve

CHAPTER FIVE • 27
Double Check Valve

Assemblies

(Figure 41)

Some field test procedures for

testing double check valve

assemblies require that the

number 1 shut-off valve be

closed to accomplish the test.

This procedure may introduce

debris such as rust and tuberculin into the valve that will

impact against check valve

number 1 or number 2 and

compromise the sealing quality.

This potential problem should

be considered prior to the

selection of the appropriate test

method.

Two test methods, one

requiring closing of the number

1 shut-off valve, and one

without this requirement are

presented below:

Method 1

Utilizing the differential

pressure gauge and not

shutting off number 1 shut-off

valve. Figure 41)

Step 1 checking check valve

number 1

1. Verify that the number 1

shut-off is open. Shut off

number 2 shut-off valve.

2. Connect the high hose to

test cock number 2.

3. Connect the low hose to

test cock number 3.

4. Open test cocks 2 and 3.

5. Open high side bleed

needle valve on test kit

bleeding the air from the

high hose. Close the high

side bleed needle valve.

6. Open low side bleed needle

valve on test kit bleeding

the air from the low hose.

Close the low side bleed

needle valve.

7. Record the differential

gauge pressure reading.

It should be a minimum

of 1 psid.

8. Disconnect the hoses.

Step 2 Checking check valve

number 2.

1. Connect the high hose to

test cock number 3.

2. Connect the low hose to

test cock number 4.

3. Open test cocks number 3

and 4.

4. Open high side bleed

needle valve on test kit

bleeding the air from the

high hose. Close the high

side bleed needle valve.

5. Open low side bleed needle

valve on test kit bleeding

the air from the low hose.

Close the low side bleed

needle valve.

6. Record the differential

gauge pressure reading.

It should be a minimum

of 1 psid.

7. Disconnect the hoses.

To check tightness of

number 2 shut-off valve, both

the check valves must be tight

and holding a minimum of

1 psid. Also, little or no

fluctuation of inlet supply

pressure can be tolerated.

The testing is performed as

follows:

1. Connect the high hose to

number 2 test cock.

2. Connect the low hose to

number 3 test cock.

3. Connect the bypass hose to

number 4 test cock.

4. Open test cocks numbers

2, 3, and 4.

5. Open high side bleed

needle valve on test kit

bleeding the air from the

high hose. Close the high

side bleed needle valve.

6. Open low side bleed needle

valve on test kit bleeding

the air from the low hose.

Close the low side bleed

needle valve.

7. The differential gauge

pressure should read a

minimum of 1 psid.

8. Open the high side control

needle valve and the bypass

hose control needle valve

on the test kit. (This

supplies high pressure

water downstream of check

valve number 2).

9. Close test cock number 2.

(This stops the supply of

any high pressure water

downstream of number 2

check valve), If the

differential pressure gauge

holds steady, the number 2

shut-off valve is recorded as

being tight. If the differential pressure gauge drops to

zero, the number 2 shut-off

valve is recorded as leaking.

28 • CROSS-CONNECTION CONTROL MANUAL

Bleed needle valves

Control

needle

valves

High side hose Low side hose

Bypass hose

Test cock No. 1

Test cock No. 2

Check valve No. 1

Test cock No. 3

Check valve No. 2

Test cock No. 4

No. 1 shut off valveNo. 2 shut off valve

FIGURE 41.
With a leaking number 2

shut-off valve, the device is, in

most cases, in a flow condition,

and the previous test readings

taken are invalid. Unless a nonflow condition can be achieved,

either through the operation of

an additional shut-off downstream, or the use of a temporary compensating bypass hose,

accurate test results will not be

achieved.

This completes the

standard field test for a double

check valve assembly. Prior to

removal of the test equipment,

the tester should insure that he

opens number 2 shut-off valve

thereby reestablishing flow. All

test data should be recorded on

appropriate forms and the test

kit drained of water.

Method 2

Utilizing “Duplex Gauge” or

individual bourdon gauges,

requires closing number 1

shut-off. (Figure 42)

Step 1 checking check valve

number 1

1. Connect the high hose to

test cock number 2.

2. Connect the low hose to

test cock number 3.

3. Open test cocks number 2

and number 3.

4. Close number 2 shut-off

valve; then close number 1

shut-off valve.

5. By means of the high side

needle valve, lower the

pressure at test cock

number 2 about 2 psi

below the pressure at test

cock number 3. If this

small difference can be

maintained, then check

valve number 1 is reported

as “tight”. Proceed to Step

number 2. If the small

difference cannot be

maintained, proceed to

Step number 3.

Step 2 checking check valve

number 2.

Proceed exactly the same

test procedure as in Step

number 1, except that the

high hose is connected to test

cock number 3 and the low

hose connected to test cock

number 4.

Step 3

1. Open shut-off valve

number 1 to repressurize

the assembly.

2. Loosely attach the bypass

hose to test cock number 1,

and bleed from the gauge

through the bypass hose

by opening the low side

needle valve to eliminate

trapped air. Close low side

needle valve. Tighten

bypass hose. Open test

cock number 1.

3. Close number 1 shut-off

valve.

4. By loosening the low side

hose at test cock number 3,

lower the pressure in the

assembly about 10 psi

below normal line

conditions.

5. Simultaneously open both

needle valves. If the check

valve is holding tight the

high pressure gauge will

begin to drop while the

low pressure gauge will

increase. Close needle

valves. If the gauge shows

that a small (no more than

5 psi) backpressure is

created and held, then the

check valve is reported as

tight. If the check valve

leaks, a pressure differential

is not maintained as both

gauges tend to equalize or

move back towards each

other, then the check valve

is reported as leaking.

With both needle valves

open enough to keep the

needles on the gauge

stationary, the amount of

leakage is visible as the

discharge from the

upstream needle valve.

CHAPTER FIVE • 29

High side hose

High side hose

Bypass hose Bypass hose

Duplex gauge

Individual Bourdon gages mounted on a board

Low side hose

Low side hose

Test cock No. 1

Test cock No. 2

Check valve No. 1

Test cock No. 3

Check valve No. 2

Test cock No. 4

No. 1 shut off valveNo. 2 shut off valve

FIGURE 42.
Chapter Six

Administration of

a Cross-Connection

Control Program

Responsibility

“containment” theory. This

approach utilizes a minimum of

backflow devices and isolates

the customer from the water

main. It virtually insulates the

customer from potentially

contaminating or polluting the

public water supply system.

While it is recognized that

“containment” does not protect

the customer within his

building, it does effectively

remove him from possible

contamination to the public

water supply system. If the

water purveyor elects to protect

his customers on a domestic

internal protective basis and/or

“fixture outlet protective basis,”

then cross-connection control

protective devices are placed at

internal high hazard locations as

well as at all locations where

cross-connections exist at the

“last free-flowing outlet.” This

approach entails extensive

cross-connective survey work on

behalf of the water superintendent as well as constant policing

of the plumbing within each

commercial, industrial and

residential account. In large

water supply systems, fixture

outlet protection crossconnection control philosophy,

in itself, is a virtual impossibility

to achieve and police due to the

quantity of systems involved,

the complexity of the plumbing

systems inherent in many

industrial sites, and the fact that

many plumbing changes are

made within industrial and

commercial establishments that

do not require the water department to license or otherwise

endorse or ratify when contemplated or completed.

In addition, internal

plumbing cross-connection

control survey work is generally

foreign to the average water

30 • CROSS-CONNECTION CONTROL MANUAL

Under the provisions of the

Safe Drinking Water Act of

1974, the Federal Government

has established, through the

EPA (Environmental Protection

Agency), national standards of

safe drinking water. The states

are responsible for the enforcement of these standards as well

as the supervision of public

water supply systems and the

sources of drinking water. The

water purveyor (supplier) is held

responsible for compliance to

the provisions of the Safe

Drinking Water Act, to include

a warranty that water quality

provided by his operation is in

conformance with the EPA

standards at the source, and is

delivered to the customer

without the quality being

compromised as a result of its

delivery through the distribution system. As specified in the

Code of Federal Regulations

(Volume 40, Paragraph 141.2,

Section (c)) “Maximum contaminant level, means the maximum permissible level of a

contaminant in water which is

delivered to the free flowing

outlet of the ultimate user of a

public water system, except in

the case of turbidity where the

maximum permissible level is

measured at the point of entry

to the distribution system.

Contaminants added to the

water under circumstances

controlled by the user, except

those resulting from corrosion

of piping and plumbing caused

by water quality, are excluded

from this definition.”

Figure 43 depicts several

options that are open to a water

purveyor when considering

cross-connection protection to

commercial, industrial, and

residential customers. He may

elect to work initially on the

INTERNAL

PROTECTION

DEVICES

FIXTURE

OUTLET

PROTECTIVE

DEVICES

Air conditioning cooling tower

Reduced pressure zone

backflow preventer

Laboratory faucet double

check valve with

intermediate vacuum breaker

Post mix

beverage

machine

Reduced

pressure zone

backflow

preventer

Reduced

pressure zone

backflow

preventer

Reduced pressure

zone backflow

preventer

Double check valve

backflow

preventer

Photo

developing

equipment

Cafeteria

cooking

Slop sink kettle

Containment device

Boiler

Dishwasher

Laboratory Sinks

Atmospheric

vacuum

breaker

Process tank

Hose

vacuum 

breaker

Backflow preventer

with intermediate

atmospheric vent

Reduced pressure

zone backflow

preventer

Dedicated

line

FIGURE 43.
purveyor and is not normally a

portion of his job description or

duties. While it is admirable for

the water purveyor to accept

and perform survey work, he

should be aware that he runs

the risk of additional liability in

an area that may be in conflict

with plumbing inspectors,

maintenance personnel and

other public health officials.

Even where extensive

“fixture outlet protection,”

cross-connection control

programs are in effect through

the efforts of an aggressive and

thorough water supply crossconnection control program,

the water authorities should also

have an active “containment”

program in order to address the

many plumbing changes that

are made and that are inherent

within commercial and industrial establishments. In essence,

fixture outlet protection

becomes an extension beyond

the “containment” program.

Also, in order for the

supplier of water to provide

maximum protection of the

water distribution system,

consideration should be given to

requiring the owner of a

premise (commercial, industrial,

or residential) to provide at his

own expense, adequate proof

that his internal water system

complies with the local or state

plumbing code(s). In addition,

he may be required to install,

have tested, and maintain, all

backflow protection devices that

would be required—at his own

expense!

The supplier of water

should have the right of entry

to determine degree of hazard

and the existence of crossconnections in order to protect

the potable water system. By so

doing he can assess the overall

nature of the facility and its

potential impact on the water

system (determine degree of

hazard], personally see actual

cross-connections that could

contaminate the water system,

and take appropriate action to

insure the elimination of the

cross-connection or the installation of required backflow devices.

To assist the water purveyor in the total administration

of a cross-connection control

program requires that all public

health officials, plumbing

inspectors, building managers,

plumbing installers, and

maintenance men participate

and share in the responsibility

to protect the public health and

safety of individuals from crossconnections and contamination

or pollution of the public water

supply system.

Dedicated Line

Figure 43 also depicts the use

of a “dedicated” potable water

line. This line initiates immediately downstream of the water

meter and is “dedicated” solely

for human consumption i.e.,

drinking fountains, safety

showers, eye wash stations, etc.

It is very important that this

piping be color coded throughout in accordance with local

plumbing regulations, flow

direction arrows added, and the

piping religiously policed to

insure that no cross-connections

to other equipment or piping

are made that could compromise water quality. In the event

that it is felt that policing of

this line cannot be reliably

maintained or enforced, the

installation of a containment

device on this line should be a

consideration.

Method of Action

(5) Equip the water authority

with backflow device test kits.

(6) Conduct meeting(s) with

the local plumbing inspection

people, building inspectors, and

licensed plumbers in the area

who will be active in the

inspection, installations and

repair of backflow devices.

Inform them of the intent of the

program and the part that they

can play in the successful

implementation of the program.

(7) Prior to initiating a survey

of the established commercial

and industrial installations,

prepare a list of these establishments from existing records,

then prioritize the degree of

hazard that they present to the

water system, i.e., plating

plants, hospitals, car wash

facilities, industrial metal

finishing and fabrication,

mortuaries, etc. These will be

the initial facilities inspected for

cross-connections and will be

followed by less hazardous

installations.

(8) Insure that any new

construction plans are reviewed

by the water authority to assess

the degree of hazard and insure

that the proper backflow

preventer is installed concurrent

with the potential degree of

hazard that the facility presents.

(9) Establish a residential

backflow protection program that

will automatically insure that a

residential dual check backflow

device is installed automatically at

every new residence.

(10) As water meters are

repaired or replaced at residences, insure that a residential

dual check backflow preventer

is set with the new or reworked

water meter. Be sure to have

the owner address thermal

expansion provisions.

CHAPTER SIX • 31

A complete cross-connection

control program requires a

carefully planned and executed

initial action plan followed by

aggressive implementation and

constant follow-up. Proper

staffing and education of

personnel is a requirement to

insure that an effective program

is achieved. A recommended

plan of action for a crossconnection control program

should include the following

characteristics:

(1) Establish a cross-connection

control ordinance at the local

level and have it approved by

the water commissioners, town

manager, etc., and insure that it

is adopted by the town or

private water authority as a

legally enforceable document.

(2) Conduct public informative

meetings that define the

proposed cross-connection

control program, review the

local cross-connection control

ordinance, and answer all

questions that may arise

concerning the reason for the

program, why and how the

survey will be conducted, and

the potential impact upon the

industrial, commercial and

residential water customers.

Have state authorities and the

local press and radio attend the

meeting.

(3) Place written notices of the

pending cross-connection

control program in the local

newspaper, and have the local

radio station make announcements about the program as a

public service notice.

(4) Send employees who will

administer the program, to a

course, or courses, on backflow

tester certification, backflow

survey courses, backflow device

repair courses, etc.
(11) Prepare a listing of all

testable backflow devices in the

community and insure that

they are tested by certified test

personnel at the time intervals

consistent with the local crossconnection control ordinance.

(12) Prepare and submit

testing documentation of

backflow devices to the State

authority responsible for

monitoring this data.

(13) Survey all commercial and

industrial facilities and require

appropriate backflow protection

based upon the containment

philosophy and/or internal

protection and fixture outlet

protection. Follow up to insure

that the recommended devices

are installed and tested on both

an initial basis and a periodic

basis consistent with the crossconnection control ordinance.

The surveys should be

conducted by personnel

experienced in commercial and

industrial processes. The owners

or owners representatives,

should be questioned as to what

the water is being used for in

the facility and what hazards

the operations may present to

the water system (both within

the facility and to the water

distribution system) in the

event that a backsiphonage or

backpressure condition were to

exist concurrent with a nonprotected cross-connection. In

the event that experienced

survey personnel are not

available within the water

authority to conduct the survey,

consideration should be given

to having a consulting firm

perform the survey on behalf of

the water department.

Cross-Connection

Control Survey

Work

connection survey will be of

benefit to him.

(3) Ask what processes are

involved within the facility and

for what purpose potable water

is used, i.e., do the boilers have

chemical additives? Are air

conditioning cooling towers in

use with chemical additives? Do

they use water savers with

chemical additives? Do they

have a second source of water

(raw water from wells, etc.) in

addition to the potable water

supply? Does the process water

cross-connect with potentially

hazardous chemical etching

tanks, etc.?

(4) Request “as-built” engineering drawings of the potable

water supply in order to trace

out internal potable lines and

potential areas of crossconnections.

(5) Initiate the survey by

starting at the potable entrance

supply (the water meter in most

cases) and then proceed with

the internal survey in the event

that total internal protective

devices and fixture outlet

protective devices are desired.

(6) Survey the plant facilities

with the objective of looking for

cross-connections at all potable

water outlets such as:

Hose bibbs

Slop sinks

Wash room facilities

Cafeteria and kitchens

Fire protection and

Siamese outlets

Irrigation outlets

Boiler rooms

Mechanical room

Laundry facilities

(hospitals)

Production floor

(7) Make a sketch of all areas

requiring backflow protection

devices.

(8) Review with the host what

you have found and explain the

findings to him. Inform him

that he will receive a written

report documenting the

findings together with a written

recommendation for corrective

action. Attempt to answer all

questions at this time. Review

the findings with the owner or

manager if time and circumstances permit.

(9) Document all findings and

recommendations prior to

preparing the written report.

Include as many sketches or

photos with the final report as

possible. If the located cross

connection(s) cannot be

eliminated, state the generic

type of backflow preventer

required at each cross connection found.

(10) Consider requiring or

recommending compliance of

the survey findings within a

definitive time frame. (if

appropriate authority is in

effect).

32 • CROSS-CONNECTION CONTROL MANUAL

Cross-connection control

survey work should only

be performed by personnel

knowledgeable about commercial and industrial potential

cross-connections as well as

general industrial uses for both

potable and process water. If

“containment” is the prime

objective of the survey, then

only sufficient time need be

spent in the facility to determine the degree of hazard

inherent within the facility or

operation. Once this is determined, a judgment can be

made by the cross-connection

control inspector as to what

type of backflow protective

device will be needed at the

potable supply entrance, or

immediately downstream of the

water meter. In the event that

the cross-connection control

program requires “total”

protection to the last free

flowing outlet, then the survey

must be conducted in depth to

visually inspect for all crossconnections within the facility

and make recommendations

and requirements for fixture

outlet protective devices,

internal protective devices, and

containment devices.

It is recommended that

consideration be given to the

following objectives when

performing a cross-connection

control survey:

(1) Determine if the survey will

be conducted with a prearranged appointment or

unannounced.

(2) Upon entry, identify

yourself and the purpose of the

visitation and request to see the

plant manager, owner, or

maintenance supervisor in order

to explain the purpose of the

visit and why the cross-
Chapter Seven

The successful promotion of

a cross-connection control

and backflow prevention

program in a municipality

will be dependent upon legal

authority to conduct such a

program. Where a community

has adopted a modern plumbing code, such as the National

Plumbing Code, ASA A40.8-

1955, or subsequent revisions

thereof, provisions of the code

will govern backflow and

cross-connections. It then

remains to provide an ordinance

that will establish a program

of inspection for an elimination

of cross- and backflow connections within the community.

Frequently authority for such

a program may already be

possessed by the water department or water authority. In

such cases no further document

may be needed. A crossconnection control ordinance

should have at least three

basic parts.

Water Department Name

Cross-Connection Control Program

I. Purpose

A. To protect the public potable water supply served by the

( ) Water Department from the possibility of contamination

or pollution by isolating, within its customers internal distribution

system, such contaminants or pollutants which could backflow or

back-siphon into the public water system.

B. To promote the elimination or control of existing crossconnections, actual or potential, between its customers in-plant

potable water system, and non-potable systems.

C. To provide for the maintenance of a continuing program

of cross-connection control which will effectively prevent the

contamination or pollution of all potable water systems by crossconnection.

II. Authority

A. The Federal Safe Drinking Water Act of 1974, and the

statutes of the State of ( ) Chapters ( ) the water

purveyor has the primary responsibility for preventing water from

unapproved sources, or any other substances, from entering the

public potable water system.

B. ( ) Water Department, Rules and Regulations,

adopted.

CHAPTER SEVEN • 33

Cross-Connection

Control and Backflow

Prevention Program

1. Authority for establishment of a program.

2. Technical provisions

relating to eliminating

backflow and crossconnections.

3. Penalty provisions for

violations.

The following model

program is suggested for

municipalities who desire to

adopt a cross-connection

control ordinance. Communities adopting ordinances should

check with State health officials

to assure conformance with

State codes. The form of the

ordinance should comply with

local legal requirements and

receive legal adoption from the

community.

CROSS CONNECTION CONTROL

MODEL PROGRAM

WATER DEPARTMENT NAME

ADDRESS

DATE

 Approved _________________

 Date _____________________
III. Responsibility

The Director of Municipal Services shall be responsible for the

protection of the public potable water distribution system from

contamination or pollution due to the backflow or backsiphonage

of contaminants or pollutants through the water service connection. If, in the judgment of the Director of Municipal Services, an

approved backflow device is required at the city’s water service

connection to any customer’s promises, the Director, or his

delegated agent, shall give notice in writing to said customer to

install an approved backflow prevention device at each service

connection to his premises. The customer shall, within 90 days

install such approved device, or devices, at his own expense, and

failure or refusal, or inability on the part of the customer to install

said device or devices within ninety (90) days, shall constitute a

ground for discontinuing water service to the premises until such

device or devices have been properly installed.

IV. Definitions

A. Approved

Accepted by the Director of Municipal Services as meeting an

applicable specification stated or cited in this regulation, or as

suitable for the proposed use.

B. Auxiliary Water Supply

Any water supply, on or available, to the premises other than

the purveyor’s approved public potable water supply.

C. Backflow

The flow of water or other liquids, mixtures or substances,

under positive or reduced pressure in the distribution pipes of a

potable water supply from any source other than its intended

source.

D. Backflow Preventer

A device or means designed to prevent backflow or

backsiphonage. Most commonly categorized as air gap, reduced

pressure principle device, double check valve assembly, pressure

vacuum breaker, atmospheric vacuum breaker, hose bibb vacuum

breaker, residential dual check, double check with intermediate

atmospheric vent, and barometric loop.

D.1 Air Gap

A physical separation sufficient to prevent backflow between

the free-flowing discharge end of the potable water system and any

other system. Physically defined as a distance equal to twice the

diameter of the supply side pipe diameter but never less than one

(1) inch.

D.2 Atmospheric Vacuum Breaker

A device which prevents backsiphonage by creating an

atmospheric vent when there is either a negative pressure or

subatmospheric pressure in a water system.

D.3 Barometric Loop

A fabricated piping arrangement rising at least thirty five (35)

feet at its topmost point above the highest fixture it supplies. It is

utilized in water supply systems to protect against backsiphonage.

D.4 Double Check Valve Assembly

An assembly of two (2) independently operating spring loaded

check valves with tightly closing shut off valves on each side of the

check valves, plus properly located test cocks for the testing of each

check valve.

D.5 Double Check Valve with Intermediate Atmospheric Vent

A device having two (2) spring loaded check valves separated

by an atmospheric vent chamber.

D.6 Hose Bibb Vacuum Breaker

A device which is permanently attached to a hose bibb and

which acts as an atmospheric vacuum breaker.

D.7 Pressure Vacuum Breaker

A device containing one or two independently operated spring

loaded check valves and an independently operated spring loaded

air inlet valve located on the discharge side of the check or checks.

Device includes tightly closing shut-off valves on each side of the

check valves and properly located test cocks for the testing of the

check valve(s).

D.8 Reduced Pressure Principle Backflow Preventer

An assembly consisting of two (2) independently operating

approved check valves with an automatically operating differential

relief valve located between the two (2) check valves, tightly

closing shut-off valves on each side of the check valves plus

properly located test cocks for the testing of the check valves and

the relief valve.

D.9 Residential Dual Check

An assembly of two (2) spring loaded, independently operating check valves without tightly closing shut-off valves and test

cocks. Generally employed immediately downstream of the water

meter to act as a containment device.

E. Backpressure

A condition in which the owners system pressure is greater

than the suppliers system pressure.

F. Backsiphonage

The flow of water or other liquids, mixtures or substances into

the distribution pipes of a potable water supply system from any

source other than its intended source caused by the sudden

reduction of pressure in the potable water supply system.

G. Commission

The State of ( ) Control Commission.

34 • CROSS-CONNECTION CONTROL MANUAL
H. Containment

A method of backflow prevention which requires a backflow

prevention preventer at the water service entrance.

I. Contaminant

A substance that will impair the quality of the water to a

degree that it creates a serious health hazard to the public leading

to poisoning or the spread of disease.

J. Cross-Connection

Any actual or potential connection between the public water

supply and a source of contamination or pollution.

K. Department

City of ( ) Water Department.

L. Fixture Isolation

A method of backflow prevention in which a backflow

preventer is located to correct a cross connection at an in-plant

location rather than at a water service entrance.

M. Owner

Any person who has legal title to, or license to operate or

habitat in, a property upon which a cross-connection inspection is

to be made or upon which a cross-connection is present.

N. Person

Any individual, partnership, company, public or private

corporation, political subdivision or agency of the State Department, agency or instrumentality or the United States or any other

legal entity.

O. Permit

A document issued by the Department which allows the use of

a backflow preventer.

P. Pollutant

A foreign substance, that if permitted to get into the public

water system, will degrade its quality so as to constitute a moderate hazard, or impair the usefulness or quality of the water to a

degree which does not create an actual hazard to the public health

but which does adversely and unreasonably effect such water for

domestic use.

Q. Water Service Entrance

That point in the owners water system beyond the sanitary

control of the District; generally considered to be the outlet end of

the water meter and always before any unprotected branch.

R. Director of Municipal Services

The Director, or his delegated representative in charge of the

( ) Department of Municipal Services, is invested with the

authority and responsibility for the implementation of a crossconnection control program and for the enforcement of the

provisions of the Ordinance.

V. Administration

A. The Department will operate a cross-connection control

program, to include the keeping of necessary records, which fulfills

the requirements of the Commission’s Cross-Connection Regulations and is approved by the Commission.

B. The Owner shall allow his property to be inspected for possible

cross-connections and shall follow the provisions of the

Department’s program and the Commission’s Regulations if a

cross-connection is permitted.

C. If the Department requires that the public supply be protected

by containment, the Owner shall be responsible for water quality

beyond the outlet end of the containment device and should utilize

fixture outlet protection for that purpose.

He may utilize public health officials, or personnel from the

Department, or their delegated representatives, to assist him in the

survey of his facilities and to assist him in the selection of proper

fixture outlet devices, and the proper installation of these devices.

VI. Requirements

A. Department

1. On new installations, the Department will provide onsite evaluation and/or inspection of plans in order to determine

the type of backflow preventer, if any, that will be required, will

issue permit, and perform inspection and testing. In any case, a

minimum of a dual check valve will be required in any new

construction.

2. For premises existing prior to the start of this program,

the Department will perform evaluations and inspections of plans

and/or premises and inform the owner by letter of any corrective

action deemed necessary, the method of achieving the correction,

and the time allowed for the correction to be made. Ordinarily,

ninety (90) days will be allowed, however, this time period may be

shortened depending upon the degree of hazard involved and the

history of the device(s) in question.

3. The Department will not allow any cross-connection to

remain unless it is protected by an approved backflow preventer for

which a permit has been issued and which will be regularly tested

to insure satisfactory operation.

4. The Department shall inform the Owner by letter, of

any failure to comply, by the time of the first re-inspection. The

Department will allow an additional fifteen (15) days for the

correction. In the event the Owner fails to comply with the

necessary correction by the time of the second re-inspection, the

Department will inform the Owner by letter, that the water

service to the Owner’s premises will be terminated within a

period not to exceed five (5) days. In the event that the Owner

informs the Department of extenuating circumstances as to why

the correction has not been made, a time extension may be

granted by the Department but in no case will exceed an additional thirty (30) days.

CHAPTER SEVEN • 35
5. If the Department determines at any time that a serious

threat to the public health exists, the water service will be terminated immediately.

6. The Department shall have on file, a list of Private

Contractors who are certified backflow device testers. All charges

for these tests will be paid by the Owner of the building or

property.

7. The Department will begin initial premise inspections to

determine the nature of existing or potential hazards, following the

approval of this program by the Commission, during the calendar

year ( ). Initial focus will be on high hazard industries and

commercial premises.

B. Owner

1. The Owner shall be responsible for the elimination or

protection of all cross-connections on his premises.

2. The Owner, after having been informed by a letter from

the Department, shall at his expense, install, maintain, and test, or

have tested, any and all backflow preventers on his premises.

3. The Owner shall correct any malfunction of the backflow

preventer which is revealed by periodic testing.

4. The Owner shall inform the Department of any proposed

or modified cross-connections and also any existing crossconnections of which the Owner is aware but has not been found

by the Department.

5. The Owner shall not install a bypass around any backflow

preventer unless there is a backflow preventer of the same type on

the bypass. Owners who cannot shut down operation for testing of

the device(s) must supply additional devices necessary to allow

testing to take place. (Ref. Fig. 33 page 23.)

6. The Owner shall install backflow preventers in a manner

approved by the Department. (Ref. Figures 3 through 37, pages 23

through 24.)

7. The Owner shall install only backflow preventers approved by the Department or the Commission.

8. Any Owner having a private well or other private water

source, must have a permit if the well or source is cross-connected

to the Department’s system. Permission to cross-connect may be

denied by the Department. The Owner may be required to install

a backflow preventer at the service entrance if a private water

source is maintained, even if it is not cross-connected to the

Department’s system.

9. In the event the Owner installs plumbing to provide

potable water for domestic purposes which is on the Department’s

side of the backflow preventer, such plumbing must have its own

backflow preventer installed.

10. The Owner shall be responsible for the payment of all fees

for permits, annual or semi-annual device testing, retesting in the

case that the device fails to operate correctly, and second reinspections for non-compliance with Department or Commission

requirements.

VII.Degree of Hazard

The Department recognizes the threat to the public water

system arising from cross-connections. All threats will be classified

by degree of hazard and will require the installation of approved

reduced pressure principle backflow prevention devices or double

check valves.

VIII. Permits

The Department shall not permit a cross-connection within

the public water supply system unless it is considered necessary and

that it cannot be eliminated.

A. Cross-connection permits that are required for each

backflow prevention device are obtained from the Department. A

fee of ( ) dollars will be charged for the initial permit and

( ) dollars for the renewal of each permit.

B. Permits shall be renewed every ( ) years and are

non-transferable. Permits are subject to revocation and become

immediately revoked if the Owner should so change the type of

cross-connection or degree of hazard associated with the service.

C. A permit is not required when fixture isolation is achieved

with the utilization of a non-testable backflow preventer.

IX. Existing in-use backflow prevention devices.

Any existing backflow preventer shall be allowed by the

Department to continue in service unless the degree of hazard is

such as to supercede the effectiveness of the present backflow

preventer, or result in an unreasonable risk to the public health.

Where the degree of hazard has increased, as in the case of a

residential installation converting to a business establishment, any

existing backflow preventer must be upgraded to a reduced

pressure principle device, or a reduced pressure principle device

must be installed in the event that no backflow device was present.

X. Periodic Testing

A. Reduced pressure principle backflow devices shall be

tested and inspected at least semi-annually.

B. Periodic testing shall be performed by the Department’s

certified tester or his delegated representative. This testing will be

done at the owner’s expense.

C. The testing shall be conducted during the Department’s

regular business hours. Exceptions to this, when at the request of

the owner, may require additional charges to cover the increased

costs to the Department.

D. Any backflow preventer which fails during a periodic

test will be repaired or replaced. When repairs are necessary,

upon completion of the repair the device will be re-tested at

owners expense to insure correct operation. High hazard situations will not be allowed to continue unprotected if the backflow

preventer fails the test and cannot be repaired immediately. In

other situations, a compliance date of not more than thirty (30)

days after the test date will be established. The owner is respon36 • CROSS-CONNECTION CONTROL MANUAL
sible for spare parts, repair tools, or a replacement device. Parallel

installation of two (2) devices is an effective means of the owner

insuring that uninterrupted water service during testing or repair

of devices and is strongly recommended when the owner desires

such continuity. (Ref. Fig. 33 page 23.)

E. Backflow prevention devices will be tested more frequently than specified in A. above, in cases where there is a history

of test failures and the Department feels that due to the degree of

hazard involved, additional testing is warranted. Cost of the

additional tests will be born by the owner.

XI. Records and Reports

A. Records

The Department will initiate and maintain the following:

1. Master files on customer cross-connection tests and/or

inspections.

2. Master files on cross-connection permits.

3. Copies of permits and permit applications.

4. Copies of lists and summaries supplied to the

Commission.

B. Reports

The Department will submit the following to the Commission.

1. Initial listing of low hazard cross-connections to the State.

2. Initial listing of high hazard cross-connections to the

State.

3. Annual update lists of items 1 and 2 above.

4. Annual summary of cross-connection inspections to the

State.

XII. Fees and Charges

The Department will publish a list of fees or charges for the

following services or permits:

1. Testing fees

2. Re-testing fees

3. Fee for re-inspection

4. Charges for after-hours inspections or tests.

Addendum

1. Residential dual check

Effective the date of the acceptance of this Cross-Connection

Control Program for the Town of ( ) all new residential

buildings will be required to install a residential dual check device

immediately downstream of the water meter. (Ref. Figure 37

page 24.) Installation of this residential dual check device on a

retrofit basis on existing service lines will be instituted at a time

and at a potential cost to the homeowner as deemed necessary by

the Department.

The owner must be aware that installation of a residential dual

check valve results in a potential closed plumbing system within

his residence. As such, provisions may have to be made by the

owner to provide for thermal expansion within his closed loop

system, i.e., the installation of thermal expansion devices and/or

pressure relief valves.

2. Strainers

The Department strongly recommends that all new retrofit

installations of reduced pressure principle devices and double check

valve backflow preventers include the installation of strainers

located immediately upstream of the backflow device. The installation of strainers will preclude the fouling of backflow devices due to

both foreseen and unforeseen circumstances occurring to the water

supply system such as water main repairs, water main breaks, fires,

periodic cleaning and flushing of mains, etc. These occurrences

may “stir up” debris within the water main that will cause fouling

of backflow devices installed without the benefit of strainers.

CHAPTER SEVEN • 37
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

38 • CROSS-CONNECTION CONTROL MANUAL

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

Ice maker

Laboratory sink, serrated nozzle

Laundry machine

Lavatory

Lawn sprinkler system

Photo laboratory sink

Sewer flushing manhole

Slop sink, flushing rim

Slop sink, threaded supply

Steam table

Urinal, siphon jet blowout

Vegetable peeler

Water closet, flush tank,

ball cock

Water closet, flush valve,

siphon jet

Appendix B

Illustrations of

Backsiphonage

The following illustrates typical

plumbing installations where

backsiphonage is possible.

Backsiphonage

Case I (Fig. 44)

A. Contact Point: A rubber

hose is submerged in a bedpan

wash sink.

B. Causes of Reversed Flow:

(I) A sterilizer connected to the

water supply is allowed to cool

without opening the air vent.

As it cools, the pressure within

the sealed sterilizer drops below

atmospheric producing a

vacuum which draws the

polluted water into the sterilizer

contaminating its contents. (2)

The flushing of several flush

valve toilets on a lower floor

which are connected to an

undersized water service line

reduces the pressure at the

water closets to atmospheric

producing a reversal of the flow.

C. Suggested Correction: The

water connection at the bedpan

wash sink and the sterilizer

should be provided with

properly installed backflow

preventers.

Backsiphonage

Case 2 (Fig. 45)

A. Contact Point: A rubber

hose is submerged in a laboratory sink.

B. Cause of Reversed Flow:

Two opposite multi-story

buildings are connected to the

same water main, which often

lacks adequate pressure. The

building on the right has

installed a booster pump.

A

B B

B

A

B

FIGURE 44.

Backsiphonage (Case 1). FIGURE 45.

Backsiphonage (Case 2).
FIGURE 48.

Backsiphonage (Case 5).

B

A

Main

Gasoline

Water

APPENDIX B • 39

When the pressure is inadequate in the main, the building booster pump starts

pumping, producing a negative

pressure in the main and

causing a reversal of flow in the

opposite building.

C. Suggested Correction: The

laboratory sink water outlet

should be provided with a

vacuum breaker. The water

service line to the booster pump

should be equipped with a

device to cut off the pump

when pressure approaches a

negative head or vacuum.

Backsiphonage

Case 3 (Fig. 46)

A. Contact Point: A chemical

tank has a submerged inlet.

B. Cause of Reversed Flow:

The plant fire pump draws

suction directly from the city

water supply line which is

insufficient to serve normal

plant requirements and a major

fire at the same time. During a

fire emergency, reversed flow

may occur within the plant.

C. Suggested Correction: The

water service to the chemical

tank should be provided

through an air gap.

Backsiphonage

Case 4 (Fig. 47)

A. Contact Point: The water

supply to the dishwasher is not

protected by a vacuum breaker.

Also, the dishwasher has a solid

waste connection to the sewer.

B. Cause of Reversed Flow:

The undersized main serving

the building is subject to

reduced pressures, and therefore

only the first two floors of the

building are supplied directly

with city pressure. The upper

floors are served from a booster

pump drawing suction directly

from the water service line.

During periods of low city

pressure, the booster pump

suction creates negative

pressures in the low system,

thereby reversing the flow.

C. Suggested Correction: The

dishwasher hot and cold water

should be supplied through an

air gap and the waste from the

dishwasher should discharge

through an indirect waste. The

booster pump should be

equipped with a low-pressure

cutoff device.

Backsiphonage

Case 5 (Fig. 48)

A. Contact Point: The gasoline

storage tank is maintained full

and under pressure by means of

a direct connection to the city

water distribution system.

B. Cause of Reversed Flow:

Gasoline may enter the

distribution system by gravity

or by siphonage in the event of

a leak or break in the water

main.

C. Suggested Correction: A

reduced pressure principle

backflow preventer should be

installed in the line to the

gasoline storage tank or a surge

tank and pump should be

provided in that line.

Backsiphonage

Case 6 (Fig. 49)

A. Contact Point: There is a

submerged inlet in the second

floor bathtub.

B. Cause of Reversed Flow:

An automobile breaks a nearby

fire hydrant causing a rush of

water and a negative pressure in

the service line to the house,

sucking dirty water out of the

bathtub.

C. Suggested Correction: The

hot and cold water inlets to the

bathtub should be above the

rim of the tub.

CHEMICALS INC.

A

B

FIGURE 46.

Backsiphonage (Case 3).

FIGURE 47.

Backsiphonage (Case 4).

B

A

FIGURE 49.

Backsiphonage (Case 6).

B

A

Main

Sewer

Dishwasher

High service

Low service
Appendix C

The following presents

illustrations of typical plumbing

installations where backflow

resulting from backpressure is

possible.

Backflow

Case I (Fig. 50)

A. Contact Point: A direct

connection from the city supply

to the boiler exists as a safety

measure and for filling the

system. The boiler water system

is chemically treated for scale

prevention and corrosion

control.

B. Cause of Reversed Flow:

The boiler water recirculation

pump discharge pressure or

backpressure from the boiler

exceeds the city water pressure

and the chemically treated

water is pumped into the

domestic system through an

open or leaky valve.

C. Suggested Correction: As

minimum protection two check

valves in series should be

provided in the makeup

waterline to the boiler system.

An air gap separation or

reduced pressure principle

backflow preventer is better.

C. Suggested Correction:

Each pier water outlet should

be protected against backflow.

The main water service to the

pier should also be protected

against backflow by an air gap

or reduced pressure principle

backflow preventer.

Backflow

Case 4 (Fig. 53)

A. Contact Point: A singlevalved connection exists

between the public, potable

water supply and the firesprinkler system of a mill.

B. Cause of Reversed Flow:

The sprinkler system is normally supplied from a nearby

lake through a high-pressure

pump. About the lake are large

numbers of overflowing septic

tanks. When the valve is left

open, contaminated lake water

can be pumped to the public

supply.

C. Suggested Correction: The

potable water supply to the fire

system should be through an air

gap or a reduced pressure

principle backflow preventer

should be used.

Illustrations of

Backpressure

Backflow

Case 2 (Fig. 51)

A. Contact Point: Sewage

seeping from a residential

cesspool pollutes the private

well which is used for lawn

sprinkling. The domestic water

system, which is served from a

city main, is connected to the

well supply by means of a valve.

The purpose of the connection

may be to prime the well

supply for emergency domestic

use.

B. Cause of Reversed Flow:

During periods of low city

water pressure, possibly when

lawn sprinkling is at its peak,

the well pump discharge

pressure exceeds that of the city

main and well water is pumped

into the city supply through an

open or leaky valve.

C. Suggested Correction: The

connection between the well

water and city water should be

broken

Backflow

Case 3 (Fig. 52)

A. Contact Point: A valve

connection exists between the

potable and the non potable

systems aboard the ship.

B. Cause of Reversed Flow:

While the ship is connected to

the city water supply system

for the purpose of taking on

water for the potable system,

the valve between the potable

and nonpotable systems is

opened, permitting contaminated water to be pumped into

the municipal supply.

B

A

A

B

City

main

Pump

To potable

system

FIGURE 50.

Backflow (Case 1).

FIGURE 51.

Backflow (Case 2).

FIGURE 52.

Backflow (Case 3).

FIGURE 53.

Backflow (Case 4).

ACME MILLS

Sprinkler

System

B

A

Chemical feeder

B

A

40 • CROSS-CONNECTION CONTROL MANUAL
2xD

Pump

Ball check

Waste line

D

Appendix D

The following illustrations describe methods of providing an

air gap discharge to a waste line which may be occasionally or

continuously subject to backpressure.

Appendix E

Illustrations of

Air Gaps

Illustrations of

Vacuum Breakers

To fire system

Float valves Nonpotable supply 2xD Potable supply

FIGURE 54.

Air gap to sewer subject to

backpressure—force main.

FIGURE 55.

Air gap to sewer subject to

backpressure—gravity drain.

FIGURE 56.

Fire system makeup tank for a

dual water system.

Brass inset

Rubber sleeve

Air vent

Air Air enters here

preventing rise of

contaminated liquids

in fixtures

Vaccum closes gate

Cowl nut

Flush connection

FIGURE 57.

Vacuum breakers.

FIGURE 58.

Vacuum breaker arrangement for

an outside hose hydrant.

Plan

“A” “A”

Exterior

building wall

1" sleeve, sch. 40.

Hand wheel

I.P.S. hose adapter

Coupling M.I. galv.

Section “A” “A” 1⁄2" or 3⁄4" Ell. m. M. I. galv.

1⁄2" or 3⁄4"

nipple galv.

1⁄2" or 3⁄4"

gate valve

1⁄2" or 3⁄4"

sch. 40. galv.

1⁄2" or 3⁄4"

vacuum breaker

(By permission of Mr. Gustave J. Angele

Sr., P.E. formerly Plant Sanitary

Engineer, Union Carbide Nuclear

Division, Oak Ridge, Tenn.)

2xD

Indirect waste

Ball check

Support vanes

Horizontal waste

D

APPENDIX E • 41
Appendix F

Effective Opening The

minimum cross-sectional

area at the point of water

supply discharge, measured

or expressed in terms of

(1) diameter of a circle, or

(2) if the opening is not

circular, the diameter of a

circle or equivalent crosssectional area.

Flood-Level Rim The edge of

the receptacle from which

water overflows.

Flushometer Valve A device

which discharges a predetermined quantity of water

to fixtures for flushing

purposes and is actuated by

direct water pressure.

Free Water Surface A water

surface that is at atmospheric pressure.

Frostproof Closet A hopper

with no water in the bowl

and with the trap and

water supply control valve

located below frost line.

Indirect Waste Pipe A drain

pipe used to convey liquid

wastes that does not

connect directly with the

drainage system, but which

discharges into the

drainage system through

an air break into a vented

trap or a properly vented

and trapped fixture,

receptacle, or interceptor.

Plumbing The practice,

materials, and fixtures

used in the installation,

maintenance, extension,

and alteration of all piping,

fixtures, appliances and

appurtenances in connection with any of the

following: sanitary

drainage or storm drainage

facilities, the venting

system and the public or

private water-supply

systems, within or

adjacent to any building,

structure, or conveyance;

also the practice and

materials used in the

installation, maintenance,

extension, or alteration of

storm water, liquid waste,

or sewerage, and watersupply 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 USEPA

National Primary Drinking Water Regulations and

the regulations of the

public health authority

having jurisdiction.

Vacuum Any absolute pressure

less than that exerted by

the atmosphere.

42 • CROSS-CONNECTION CONTROL MANUAL

Glossary

Air gap The unobstructed

vertical distance through

the free atmosphere

between the lowest

opening from any pipe or

faucet supplying water to a

tank, plumbing fixture, or

other device and the floodlevel rim of the receptacle.

Backflow The flow of water or

other liquids, mixtures, or

substances into the

distributing pipes of a

potable supply of water

from any source or sources

other than its intended

source. Backsiphonage is

one type of backflow.

Backflow Connection Any

arrangement whereby

backflow can occur.

Backflow Preventer A device

or means to prevent

backflow. Backflow

Preventer, Reduced

Pressure Principle Type

An assembly of differential

valves and check valves

including an automatically

opened spillage port to the

atmosphere.

Backsiphonage Backflow

resulting from negative

pressures in the distributing pipes of a potable water

supply.

Cross-Connection Any actual

or potential connection

between the public water

supply and a source of

contamination or pollution.

Vacuum Breaker A device

that permits air into a

water supply distribution

line to prevent

backsiphonage.

Water Outlet A discharge

opening through which

water is supplied to a

fixture, into the atmosphere (except into an open

tank which is part of the

water supply system), to a

boiler or heating system, to

any devices or equipment

requiring water to operate

but which are not part of

the plumbing system.

Water Supply System The

water service pipe, the

water-distributing pipes,

and the necessary connecting pipes, fittings, control

valves, and all appurtenances in or adjacent to

the building or premises.

The water supply system

is part of the plumbing

system.
APPENDIX G • 43

Appendix G

Bibliography

Accepted Procedure and Practice in

Cross-Connection Control

Manual, American Water

Works Association, Pacific

Northwest Section, 4th Edition.

Nov. 1985.

American Backflow Prevention

Association, P.O. Box 1563

Akron, Ohio 44309-1563.

Angele, Gustave Cross-Connection

and Backflow Prevention,

American Water Works

Association. Supplementary

Reading library Series – No.

S106, New York 10016.

A Revision of The Notional Plumbing

Code, ASA A40.8-1955, Report

of the Public Health Service

Technical Committee on

Plumbing Standards. Sept. 15,

1962, Public Health Service,

Washington 25, D.C.

AWWA Standard For Backflow

Prevention Devices - Reduced

Pressure Principle and Double

Check Valve Types (C509-78),

American Water Works

Association, Denver, Colorado,

Reaffirmed 1983. Backflow

Prevention and Cross-Connection Control, AWWA Manual

M14, American Water Works

Association, Denver, Colorado

1966.

Backflow Prevention and CrossConnection Control, Ohio EPA,

Office of Public. Water Supply.

Second Edition, Revised Mar.

15, 1977. Backflow Prevention

Devices—Selection, Installation,

Maintenance, and Field Testing,

CSA Standard B64.10M1981.

Canadian Standards Association,

Dec.1981.

Backflow—The Manual of CrossConnection Prevention in Public

Water Supplies, Missouri Dept. of

Natural Resources.

Canadian Plumbing Code 1980,

NRCC, No. 17305, Second

Printing, Issued by the

Associate Committee on the

National Building Code,

Natural Research Council of

Canada, Ottawa.

Control and Elimination of CrossConnections, Panel Discussion,

Journal American Water Works

Association, Vol.50, No.1, 1960.

Cross-Connection Complications,

The Capital’s Health, Vol. 11,

No. 9, Dec. 1953, D.C. Dept. of

Public Health, Washington,

D.C.

Cross-Connection Control, American

Water Works Association,

British Columbia Section,

Second Edition, Jan.1980. CrossConnection Control and Backflow

Prevention Device Testing, New

England Water Works Association, August 1987.

Cross-Connection Control and Backflow

Prevention, Practice and Procedure

Manual, Administrative Manual,

City of Winnipeg, Manitoba.

Third Edition, April 1980.

Cross-Connection Control, Backflow

Prevention Device Tester

Certification Training Course,

Public Drinking Water

Program, Division of Environmental Quality, Department of

Natural Resources, State of

Missouri.

Cross-Connection Control Manual,

Division of Sanitary Engineering, Tennessee Dept. of Public

Health, 1975.

Cross-Connection Control Regulation in Washington State,

Washington State Dept. of

Social and Health Services,

Denver, Colorado, 1974. Second

Edition.

Cross-Connection Control, New

York State Dept. of Health,

Jan.1981.

Cross-Connection Control Program,

State of Utah, Oct.1985, Travis

Black.

Cross-Connection Control, Water

Quality Division, Colorado

Department of Health. Revised

March 1983. Cross-Connection

Control Survey, New England

Water Works Association,

August 1987.

CSA Standards on Vacuum Breakers

and Backflow Preventers, B64

Series 1976 Canadian Standards

Association, Dec.1976.

Dawson, F. M., and Kalinske, A.

A., Report on Cross-Connections

and Backsiphonage Research,

Technical Bulletin No. 1,

National Association of

Plumbing, Heating, Cooling

Contractors, Washington, D.C.

Evaluation of Backflow Prevention

Devices—A State of the Art, (N B

SIR 76-1070) U.S. Environmental Protection Agency, Water

Supply Division, Washington,

D.C., June 1976.

Hendrickson, Howard D. CrossConnection Control, Part 1 & 2,

August & September 1981

issues of Reeves Journal.

How To Prevent Industrial CrossConnection Dangers, Water

Works Engineering, Feb. 1962.

Manitoba Plumbing Code 1981,

Issued by the Department of

Labour and Manpower of the

Province of Manitoba.

Manual of Cross-Connection

Control, Dept. of Health and

Hospitals, Denver, Colorado,

1977.

Manual of Cross-Connection

Control, Foundation for CrossConnection Control and

Hydraulic Research, University

of Southern California, 7th

Editions, June 1985.

Manual of Cross-Connection

Control Practices and Procedures, State of California, Health

and Welfare Agency, July 1981.

Plumbing and Drainage Act

Regulations, Alberta, as amended

by Alberta Regulations (295/80).

Regulations Relating To CrossConnections, excerpt from the

California Administrative Code,

Title 17, Public Health, 1956.

Saskatchewan Regulations 8/78,

Regulations Governing

Plumbing and Drainage

Solar Domestic Hot Water Systems and

the Water Purveyor, American

Water Works Association,

Pacific Northwest Section.

Springer, E. K., and Reynolds, K.

C., Definitions and Specifications of

Double Check Valve Assemblies and

Reduced Pressure Principle Backflow

Prevention Devices, University of

Southern California, School of

Engineering Dept. 48-101, Jan.

30, 1959.

Taylor, F. B., and Skodje, M. T.,

Cross-Connections, A Hazard in

All Buildings, Modern Sanitation

and Building Maintenance,

Vol.14, No.8, Aug. 1962.

Use of Backflow Preventers for

Cross-Connection Control, Joint

Committee Report, Journal

American Water Works

Association, Vol. 50, No.12,

Dec. 1958.

Van Meter, R. O., Backflow

Prevention Hardware, Water and

Wastes Engineering, Pt. 1, Sept.

1970; Pt. 2, Oct. 1970.
44 • CROSS-CONNECTION CONTROL MANUAL

Appendix H

Cross-Connection

Survey Form

Date: _______________________________________

Name of Company, Corporation, or Business: ______________________________________________________________

________________________________________________________________________________________________________

Address: _________________________________________________________________________________________________

Name of Contact: __________________________________________________________________________________________

Type of Use: Industrial _________ Commercial _________ Governmental _________ Other

Location of Service: _________________________________________________________________________________________

Size of Service: ___________________________ Inch Metered? Yes  No 

Require non-interrupted water service? Yes  No 

Does Boiler Feed utilize chemical additives? Yes  No 

Is Backflow protection incorporated? Yes  No 

Are air conditioning cooling towers utilized? Yes  No 

Is Backflow protection incorporated? Yes  No 

Is a Water Saver utilized on condensing lines or cooling towers? N/A  Yes  No 

Is the make-up supply line backflow protected? Yes  No 

Is process water in use, and if so, is it potable supply water or “Raw” water N/A  Potable 

Raw  Protected  Unprotected 

Is fire protection water separate from the potable supply? Yes  No 

Are Containment Devices in place? Yes  No 

Summary

Degree of Hazard: High  Low 

Type of Device recommended for containment: RPZ  DCV  None 

Fixture Outlet protection required? Yes  No 

If so, where?

______________________________________________________________________________________________
Appendix I

Backflow Prevention Device

Test and Maintenance Report

To: __________________________________________________________________________

(water purveyor or regulatory agency)

_____________________________________________________________________________

_____________________________________________________________________________

Attn: Cross-connection Control Section

The cross-connection control device detailed hereon has been tested and maintained as required by the

(rules or regulations) of (purveyor or regulatory agency) and is certified to comply with these (rules or

regulations).

Make of device ________________ size ___________________________________

Model Number ________________ located at ______________________________

Serial Number ________________ ______________________________________

 ______________________________________

Reduced Pressure Devices

The above is certified to be true.

Firm Name ______________________ Certified Tester _______________________________

Firm Address _____________________ Cert. Tester No. ________________ Date _________

 _______________________________

Pressure Vacuum Breaker

Double Check Devices Relief Valve Air Inlet Check Valve

1st Check 2nd Check

Initial Test

DC - Closed

Tight 

RP - ______ psid

Leaked 

Closed Tight 

Leaked 

Opened at

______ psid

Opened at

______ psid

Did not open 

______ psid

Leaked 

Repairs and

Materials Used

Test After Repair

DC-Closed Tight

RP- ______ psid

Closed Tight  Opened at

______ psid

Opened at

______ psid

______ psid
$300

Penalty for Private UseOfficial BusinessWashington, DC 20460AgencyEnvironmental ProtectionUnited StatesWH-550

February 2003www.epa.gov/safewaterEPA 816-R-03-002Office of Water (4606M)