Page 289 - Water Engineering Hydraulics, Distribution and Treatment

Chapter9
Cross-Connection Control
continual protection of the water in the public
9.1 INTRODUCTION
water distribution system. Customers, together
Plumbing cross-connections, which are defined as actual
with other authorities, are responsible for pre-
or potential connections between a potable and nonpotable
venting contamination of the private plumbing
water supply, constitute a serious public health hazard.
system under their control and the associated
There are numerous, well-documented cases where cross-
protection of the public water system. (Reprinted
connections have been responsible for contamination of
by permission. Copyright © 2009, American
drinking water and have resulted in the spread of disease.
Water Works Association.)
The problem is a dynamic one, because piping systems are
continually being installed, altered, or extended. Public health officials have long been concerned about
Control of cross-connections is possible, but only cross-connections and backflow connections in plumbing
through thorough knowledge and vigilance. Education is systems and in public drinking water supply distribution sys-
essential, because even those who are experienced in pip- tems. Such cross-connections, which make possible the con-
ing installations fail to recognize cross-connection possi- tamination of potable water, are ever-present dangers. One
bilities and dangers. All municipalities with public water example of what can happen is an epidemic that occurred in
supply systems should have cross-connection control pro- Chicago in 1933. Old, defective, and improperly designed
grams. Those responsible for institutional or private water plumbing and fixtures permitted the contamination of drink-
supplies should also be familiar with the dangers of cross- ing water. As a result, 1,409 people contracted amebic dysen-
connections and should exercise careful surveillance of their tery, and 98 of them died. This epidemic, and others resulting
systems. The American Water Works Association (AWWA) from contamination introduced into a water supply through
stated the following in a policy on public water supply improper plumbing, made clear the responsibility of public
matters: health officials and water purveyors for exercising control
over public water distribution systems and all plumbing sys-
AWWA recognizes water purveyors have the tems connected to them. This responsibility includes advis-
responsibility to supply potable water to their ing and instructing plumbing installers in the recognition and
customers. In the exercise of this responsibility, elimination of cross-connections.
water purveyors or other responsible authorities Cross-connections are the links through which it is pos-
must implement, administer, and maintain ongo- sible for contaminating materials to enter a potable water sup-
ing backflow prevention and cross-connection ply. The contaminant enters the potable water system when
control programs to protect public water systems the pressure of the polluted source exceeds the pressure of the
from the hazards originating on the premises potable source. The action may be called backsiphonage or
of their customers and from temporary connec- backflow. Essentially it is the reversal of a hydraulic gradient,
tions that may impair or alter the water in the and it can be produced by a variety of circumstances.
public water systems. The return of any water One might assume that the steps for detecting and elim-
to the public water system after the water has inating cross-connections would be elementary and obvious.
been used for any purposes on the customer’s The reality, however, is that cross-connections can appear
premises or within the customer’s piping system in many subtle forms and in unsuspected places. Reversal
is unacceptable and opposed by AWWA. The of pressure in the water may be freakish and unpredictable.
water purveyor shall assure that effective back- The probability of contamination of drinking water through a
flow prevention measures commensurate with cross-connection occurring within a single plumbing system
the degree of hazard are implemented to ensure may seem remote, but considering the multitude of similar

Water Engineering: Hydraulics, Distribution and Treatment, First Edition. Nazih K. Shammas and Lawrence K. Wang.
© 2016 John Wiley & Sons, Inc. Published 2016 by John Wiley & Sons, Inc.

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