Recommended Practice for Backflow Prevention and Cross-Connection Control

126 Pages·2004·14.201 MB·English

Recommended Practice for
Backflow Prevention and
Cross-Connection Control
MANUAL OF WATER SUPPLY PRACTICES M14 Third Edition
AWWA MANUAL M14
Copyright (C) 2004 American Water Works Association All Rights Reserved
MANUAL OF WATER SUPPLY PRACTICES-M14, Third Edition
Recommended Practice for Backflow Prevention and
Cross-Connection Control
Copyright 0 1973, 1989, 2004 American Water Works Association
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any
means, electronic or mechanical, including photocopy, recording, or any information or retrieval system,
except in the form of brief excerpts or quotations for review purposes, without the written permission of
the publisher.
Project Manager: Mary Kay Kozyra
Production Editor: Carol Stearns
Library of Congress Cataloging-in-PublicationD ata
Recommended practice for backflow prevention and cross-connection control.--3rd ed.
p. cm. -- (AWWA manual ; M14)
Includes bibliographical references and index.
ISBN 1-58321-288-4
1. Backsiphonage (Plumbing)--Prevention. 2. Cross-connections (Plumbing)--Standards.
I. American Water Works Association. 11. Series.
TD49LA49 no. M14 2004
LTH65231
628.1 s--dc22
[696'. 11
2003063633
Printed in the United States of America
American Water Works Association
6666 West Quincy Avenue
Denver, CO 80235-3098
ISBN 1-58321-288-4
Printed on recycled paper
Copyright (C) 2004 American Water Works Association All Rights Reserved
Figures
1-1 Examples of backflow-prevention equipment locations, 3
3-1 Schematic of a vacuum, 30
3-2 Backsiphonage backflow due to high rate of water withdrawal, 32
3-3 Backsiphonage backflow caused by reduced pressure on
suction side of booster pump, 33
3-4 Backsiphonage backflow caused by shutdown of water system, 33
3-5 Backpressure backflow caused by carbon dioxide cylinder, 35
3-6 Backpressure backflow caused by pumping system, 36
4- 1 Air gap on tank, 42
4-2 Air gap on lavatory, 43
4-3 Typical air-gap applications, 43
4-4 Additional typical air-gap applications, 44
4-5 Reduced-pressure principle backflow-prevention assembly, 45
4-6 Both check valves open and the differential relief valve closed, 46
4- 7 Both check valves closed and the differential relief valve open, 46
4-8 Backpressure: both check valves closed and the differential relief valve
closed, 46
4-9 Backsiphonage: both check valves closed and the differential relief valve
open, 47
4-10 Typical reduced-pressure principle backflow-prevention applications, 48
4-11 Double check valve assembly, 49
4-12 Check valves open, permitting flow, 50
4- 13 Negative supply pressure, check valves closed, 50
4-14 Backpressure: both check valves closed, 50
4-15 Typical double check valve assembly applications, 5 1
4- 16 Pressure vacuum-breaker assembly, 53
4-17 Pressure vacuum-breaker assembly, normal flow condition, 53
4-18 Pressure vacuum-breaker assembly, backsiphonage condition, 54
4-19 Atmospheric vacuum breaker, 57
4-20 Dual check device, 58
5- 1 Cross-connection control, water treatment plants, 83
5-2 Service-containment and area-isolation water treatment plants, 84
A- 1 Major component parts of a five-valve differential pressure gauge, 88
A-2 Illustration of an RPBA test with a differential pressure gauge, 89
V
Copyright (C) 2004 American Water Works Association All Rights Reserved
A-3 Illustration of a DCVA test with a differential pressure gauge, 91
A-4 Illustration of a PVBA test with a differential pressure gauge, 93
A-5 Shutoff with test adaptors for use on test cock, 94
A-6 Use of bypass hose, 95
A-7 Use of bypass hose for downstream shutoff test, 95
A-8 Illustration of pressure vacuum breaker, 96
A-9 Illustration of pressure vacuum breaker with differential
pressure gauge, 97
A-10 Illustration of pressure vacuum breaker with differential
pressure gauge (step 2), 98
A-11 Illustration of a double check valve assembly with differential
pressure gauge, 99
A-12 Illustration of a double check valve assembly with differential
pressure gauge (step 2), 100
A-13 Illustration of a double check valve assembly with differential
pressure gauge-test for no. 2 shuoff valve test, 101
A- 14 Illustration of reduced-pressure principle backflow preventer
test (step l),1 03
A-15 Illustration of reduced-pressure principle backflow preventer
test (step 2), 104
A-16 Illustration of reduced-pressure principle backflow preventer
test (steps 3 and 41, 105
A-17 Illustration of SVBA, 106
A-18 Illustration of an SVBA test with a differential pressure gauge, 106
vi
Copyright (C) 2004 American Water Works Association All Rights Reserved
3-1 Means of backflow prevention, 40
5-1 Recommended protection at fxtures and equipment found in water treatment
plants, 82
vii
Copyright (C) 2004 American Water Works Association All Rights Reserved
Contents
List of Figures, v
List of Tables, vii
Acknowledgments, ix
. . . . . . . . . . . . . . . . . . .
Chapter 1 Introduction. 1
Purpose of Manual, 1
Responsibilities, 1
Health Aspects, 3
Legal Aspects, 6
. . . . . . . . . . . . . . .
Chapter 2 Program Administration 11
Types of Programs, 11
Components of Water Purveyor’s Program, 13
. . . . . . . . . . . . . . . . .
Chapter 3 Backflow Principles 29
Basic Hydraulics, 29
Types of Backflow, 31
Assessing Degrees of Hazard, 34
Assessing the Effectiveness of Assemblies and Devices, 38
Chapter 4 Backflow-P.r e.v e.n ti.o n. A s.s e.m b.l y. A .p p.li c.a ti.o n., In.s t.a ll.a ti.o n., . .
and Maintenance 41
Backflow Control Methods, 42
Backflow Devices, 56
Testing, 59
. . . . . . . . . . . . . . . . . .
Chapter 5 Typical Hazards 63
Recommended Protection for Specific Categories of Customers, 63
Recommended Protection for Water Purveyor’s Hazards, 80
Appendix A Assembly Test Procedures, 85
Appendix B Model Ordinance, 109
Appendix C Common Symbols, 117
Appendix D AWWA Policy Statement on Cross-Connections, 119
Appendix E Abbreviations of Agencies and Organizations, 121
Appendix F Web Sites for Backflow-Prevention Incidents, 123
Glossary, 125
Index, 131
...
111
Copyright (C) 2004 American Water Works Association All Rights Reserved
AWWA MANUAL
1
Chapter
Introduction
PURPOSE OF MANUAL
This manual provides guidance to water purveyors on the recommended procedures
and practices for operating a cross-connection control program. The purpose of any
such program is to reduce the risk of contamination or pollution of the public water
system.
A cross-connection is an actual or potential connection between any part of a
potable water system and any other environment that contains other substances that,
under any circumstances, would allow such substances to enter the potable water sys-
tem. Other substances include gases, liquids, or solids, such as chemicals, water prod-
ucts, steam, water from other sources (potable or nonpotable), and any matter that
may change the color or taste of water or add odor to water.
RES PONS1B I L ITIES
In the United States, the federal government, under the Safe Drinking Water Act
(SDWA) 42 U.S.C. Q 300f to 3OOj-26, has jurisdiction over the public health aspects of
the drinking water supply. State governments also have jurisdiction over matters of
public health related to the supply of water. The state regulations cannot supersede
the federal regulations; however, they may be more stringent than the federal regula-
tions. Lower levels of government within a state, with the authority of the state,
may impose other regulations or more stringent regulations not in conflict with
state regulations.
In Canada, the provincial governments have jurisdiction over the public health
aspects of the drinking water supply. Lower levels of government within a province
(e.g., regional districts and municipalities), with the authority of the province, may
impose other regulations or more stringent regulations not in conflict with provincial
regulations.
Because there is a difference between the authority of the United States federal
government and that of Canada and between the different states and provinces, the
following discussion, although referring to “federal and state,” illustrates the different
regulations governing a public water utility.
1
Copyright (C) 2004 American Water Works Association All Rights Reserved
2 BACKFLOW PREVENTION AND CROSS-CONNECTION CONTROL
The federal and state governments regulate the public health aspects of the sup-
ply of drinking water “to protect the health, safety, or welfare of the users of water.”
These regulatory or “police” powers govern the manufacturers and distributors of
water (e.g., water utilities, bottled water plants, etc.). Regulations apply to the entity
that owns (controls) the facilities for the manufacture andor distribution of water.
For US water utilities (water purveyors), the SDWA regulations govern public
water systems. The SDWA (see 42 U.S.C. 300f(4)(A))s tates: “The term public water sys-
tem [PWS] means a system for the provision to the public of water for human consump-
tion through pipes or other constructed conveyances, if such system has at least 15
service connections or regularly serves at least 25 individuals. The public water system
includes (i) any collection, treatment, storage and distribution facilities under control
of the operator of such system and used primarily in connection with such system, .. . .”
A government body that owns a water utility (e.g., a city) is regulated by the
higher levels of government. All water utilities manufacture or provide a product (pota-
ble water) and, like other industries, are regulated by government. Except for certain
types of noncommunity systems where water consumption is solely within the property
owned by the water purveyor, the federal, state, and local regulatory jurisdiction over a
public water system ends at the water purveyor’s point of service. Downstream of the
point of service, federal, state, and local responsibilities “to protect the health, safety, or
welfare of the users of water” fall under the jurisdiction of agencies other than those
regulating public water systems, and include, but are not limited to, the following:
Building and plumbing officials who are responsible for regulating the potable
water system (plumbing) past the point of service. Their work generally con-
sists of reviewing plans and inspecting plumbing of permitted new or remod-
eled construction.
Fire marshals who are responsible for regulating fire protection systems (e.g.,
fire sprinkler systems) downstream of the potable water system supply con-
nection entering the premises.
Safety inspectors (Occupational Safety and Health Administration [OSHA],
Workers’ Compensation Board [WCBI [Canada], Mine Safety and Health
Administrators [MSHAI)w ho are responsible for inspecting potable water sys-
tems (plumbing) for workers’ safety.
Health officials who are responsible for inspecting restaurants and other food
preparation facilities (e.g., dairies), health care facilities (e.g., nursing homes),
etc.
Agricultural inspectors who are responsible for the safe handling of chemicals
(e.g., pesticides) used in growing and processing agricultural products.
These agencies have jurisdiction over all work on the customer’s premises. All
have regulations that involve cross-connection control. These different regulations
may be in conflict with the procedures for cross-connection control. The authority of
these agencies over the water purveyor’s customers may be continuing or may be lim-
ited by the issuance of a final permit (e.g., for building occupancy) (see Figure 1-1).
The water purveyor is not given authority to exercise any of the above-noted reg-
ulatory responsibilities without an agreement for an assignment of authority. Thus,
the water purveyor has no authority, hence no responsibility, beyond the meter for the
customer’s compliance with cross-connection regulations.
The water purveyor’s responsibility is to supply potable water to its customers at
the point of delivery (e.g., water meter). The characteristics of potable water are
defined by regulations. The testing of water quality (e.g., for lead and copper levels)
may involve collecting water samples on the customer’s premises. However, this does
not impose a responsibility on the water purveyor for regulating plumbing. As stated
in the USEPA Safe Drinking Water Act, “Maximum contaminant level means the
Copyright (C) 2004 American Water Works Association All Rights Reserved
INTRODUCTION 3
Public
Water : Uniform Plumbing Code Jurisdiction
Supply
Jurisdiction
m I i
3 Water Meter Backflow-Prevention
:
a, Equipment
.C_ t
. t
I&QI:, Plumbing Statute Applies
2 :
a.
A. Location on private side of property line
Property Line
Backflow-Prevention Fixture Protection
Equipment for per Uniform Plumbing
Premises Isolation Code Within Premises
B. Location on public entity side of property line
Courtesy of Washington Department of Health
Figure 1 - 1 Examples of backflow-prevention equipment locations
maximum permissible level of a contaminant in water which is delivered to any user
of a public water system.”
HEALTH ASPECTS
Protection of drinking water for public health emphasizes preventing contamination.
A multiple-barrier approach is used from the source to the tap. The following are
major barriers established for public water systems:
Sources of supply: Prevent human contaminants such as viruses and bac-
teria or chemicals from entering the water supply through watershed control
and wellhead protection programs.
Treatment: Remove or reduce natural and human contaminants to comply
with the maximum contaminant levels (MCLs) established by regulations.
Copyright (C) 2004 American Water Works Association All Rights Reserved
4 BACI(FL0W PREVENTION AND CROSS-CONNECTION CONTROL
Chlorination: Maintain chlorine residual in the water supply to control
microbiological quality.
Storage: Provide covered storage and prevent microbiological contamina-
tion through openings in reservoirs.
Distribution: Comply with installation and material standards and provide
minimum operating pressures to prevent contaminants from entering the sys-
tem.
Cross-connection control: Provide premises isolation (containment of ser-
vice) or equivalent in-premises fixture protection to prevent contaminants
from entering the water purveyor’s system.
Water quality monitoring: Provide surveillance of system to detect con-
taminants in the water supply.
System operator: Ensure that qualified personnel operate public water
systems through operator certification.
Emergency plan: Establish procedures for correcting problems detected in
water quality monitoring or caused by natural disasters.
On the customer’s premises, plumbing and health codes establish minimum
design, installation, and operating requirements for public health protection. Major
items in the plumbing codes are as follows:
Distribution: Install approved materials and follow design requirements to
ensure adequate pressure at furtures.
Cross-connection control: Provide backflow preventers at furtures to pre-
vent contaminants from entering the system.
Licensed plumber: Require that a licensed plumber (with some exceptions)
install and repair all plumbing.
These requirements are conservative. They include a high safety factor for sys-
tem design (reliability) and for acceptable contaminant levels. For example, regulation
of chemical contaminants may be based on a possible adverse health effect from the
long-term (e.g., lifetime) consumption of 2 liters of water per day with a chemical at a
level above the MCL.
Most SDWA requirements deal with possible chronic (long-term) health effects.
Contamination of a water distribution system through a cross-connection often results
in acute (immediate adverse) health effects that may result in illness or death of one
or more persons and/or financial losses. Although cross-connection control is only one
of the multiple barriers to protect water quality, it is one of the most important. With-
out the water purveyor’s cross-connection control program, the distribution system
may become the weak link in the multiple-barrier approach.
Potable water is water that does not contain objectionable pollution, contamina-
tion, minerals, or infectious agents and is considered satisfactory for drinking. By this
definition, potable water need not be pure or ultrapure. Potable water may contain
bacteria (e.g., low levels of heterotrophic bacteria) and other Contaminants. For cross-
connection control purposes, potable water is considered to be safe for human consump-
tion, i.e., free from harmful or objectionable materials as described by the health author-
ity. In assessing the degree of hazard, “safe for human consumption” or “free from
harmful or objectionable materials” are not clearly defined parameters. A chemical
toxin in high concentrations may cause no harm when consumed in low concentrations.
In assessing the actual and potential degrees of hazard, microbiological, chemi-
cal, and physical parameters must be considered. These parameters are described in
the following paragraphs.
Copyright (C) 2004 American Water Works Association All Rights Reserved