Q. What is backflow?
The City of Mesa's water distribution system is designed to
keep the water flowing to the customer. However, when hydraulic
conditions within the system.ate from the "normal"
conditions, water flow can be reversed. When this backflow
happens, contaminated water can enter the distribution system.
Q. What causes backflow?
Backflow is possible in two situations, backsiphonage and
Q. What is backsiphonage?
When there is a sudden reduction in the water pressure in
the distribution system, such as during firefighting or when a
water main breaks, water flow can be reversed. This can create
a suction effect, drawing the non-potable substance into the
potable water system.
Q. What is backpressure?
Backpressure is created when pressure in a non-potable
system, such as in a re-circulating system containing soap,
acid, or antifreeze, exceeds that in the potable system that
provides makeup water to the system. This can force the potable
water to reverse its direction of flow through the cross
connection. Non-potable substances can then enter the potable
Q. How can backflow be prevented?
Backflow prevention.ces: Air Gap Double Check Valve
Assembly Reduced Pressure Principal Assembly Pressure Vacuum
Breaker Assembly The type of protection required is based on the
degree of hazard to the potable water supply.
Q. What is a backflow assembly?
A backflow prevention.se is an approved, testable
assembly which uses valves, in different configurations, to
prevent polluted or contaminated water from reversing direction
and flowing backward.
Q. How is an assembly approved?
An approved backflow prevention assembly has gone through an
approval process at the
Foundation for Hydraulic Research and Cross Connection Control
at the University of Southern California. This is a
two-step process consisting of laboratory tests and a
twelve-month field test. Only assemblies completing the entire
testing procedure are recognized by City of Mesa Water as
approved backflow prevention assemblies.
Q. Who is required to have a backflow prevention
Federal and State law require that water suppliers protect
their water systems from contamination. State regulations
exempt single family residences used solely for residential
purposes from assembly requirements. However, residences used
for other purposes, as well as commercial and industrial
customers, are required by City Ordinance and State
Administrative Code rule R18-4-115 to install and maintain
backflow prevention assemblies.
Q. How do I know if I need a backflow prevention
A City of Mesa Water Backflow Prevention Inspector will
visit your property to do an evaluation for backflow
Q. My property is served with reclaimed water. Do I
need backflow protection?
Yes. Customers receiving reclaimed water must install a
Reduced Pressure Assembly (RPA) backflow preventer on all
potable water connections, including fire services.
Q. Who can install a backflow prevention assembly?
The installation of the backflow prevention assembly is the
responsibility of the customer. The assembly may be installed
by a property owner, plumbing contractor, or a general
contractor, subject to the Rules and Statutes of the Arizona
Registrar of Contractors. Permits are required to install or
replace these assemblies. Permits are issued by the City of
Q. Where should a backflow prevention assembly be
Generally, the backflow prevention assembly must be located
as close as possible to the water service connection, but must
remain on private property.
Q. Who is responsible for the testing and
maintenance of the backflow assembly?
It is the sole responsibility of the customer to ensure that
the assembly is in satisfactory operating condition at all
times. The City of Mesa will send notices to the customer
advising them when an annual test is required on their backflow
assembly. The customer must contact a recognized Backflow
Assembly Tester to perform the test. If any repair work or
maintenance is performed on the assembly, a recognized Tester
must retest the assembly immediately and submit the test results
to the City of Mesa.
Q. How do I find an approved Certified Tester?
The City of Mesa has a list of recognized Assembly Testers
that can be provided upon request from Water Resources-Backflow
Prevention. Due to the fact that test prices vary among testers,
you may want to call several Certified Testers to obtain quotes
for your test.