What is backflow?
Tucson Water's system is designed to keep the water flowing from our distribution system to customers. When hydraulic conditions within Tucson Water's system deviate from normal, the direction of the water flow can be reversed. This creates a backflow condition and the potential for contaminated water entering the distribution system.
How can backflow occur?
Backflow can occur two different ways, by backsiphonage and backpressure.
What is backsiphonage?
When there is a sudden reduction in the water pressure in the distribution system, such as during  fire fighting or when a water main breaks, water flow can be reversed. This can create a suction effect, drawing potential contaminates into the potable water distribution system.
What is backpressure?
Backpressure is created when pressure in a nonpotable system, such as in a recirculating system containing soap, acid, or antifreeze, exceeds the pressure in the potable system providing the makeup water. This can force the potable water to reverse its direction of flow through the cross-connection between the two systems. Potential contaminates can then enter the potable water system.
How can backflow be prevented?

Tucson Water recognizes four methods of backflow prevention:

  • Air Gap
  • Double Check Valve Assembly
  • Reduced Pressure Principal Assembly
  • Pressure Vacuum Breaker Assembly
Tucson Water will determine which type of protection is required based on the degree of hazard that the property represents to the potable water supply.
What is a backflow prevention assembly?
A backflow prevention assembly is an approved, testable assembly which uses valves, in different configurations, to prevent potential contaminates from flowing into the potable water system.
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 successfully completing the entire testing procedure are recognized by Tucson Water's approved backflow prevention assemblies.
Who is required to have a backflow prevention assembly?
Federal and State law requires that water suppliers protect their water systems from contamination. State regulations exempt single family residences used solely for residential purposes from the requirement to install a backflow prevention assembly. When a determination is made by Tucson Water that the potable water system may be subject to contamination through a backflow condition. Tucson Water makes these decisions on a case-by-case basis. Residential, commercial, and industrial customers, which meet the criteria in City Ordinance #9976 and State Administrative Code R18-4-215 must install and maintain backflow prevention assemblies.
How do I know if I need a backflow prevention assembly?
A Tucson Water Cross Connection Control Specialist (CCCS) will visit your property to do an evaluation for backflow requirements. The CCCS will leave or mail a "Notice of Compliance or Non-Compliance Backflow Prevention Inspection Report." This report will outline the actions you need to take.
Is there a general compliance schedule and process?
Yes. Unless you make other arrangements with Tucson Water, the backflow prevention assembly must be in compliance by the due date on the Backflow Prevention Assembly Test & Maintenance Report. The Backflow Prevention Assembly Test & Maintenance Report is mailed out 45 days before the due date. If your Assembly has not been tested and in compliance by the due date, then Tucson Water will issue a notice informing you that your water service may be discontinued in four days and a non-compliance fee will be assessed to your water bill. If at any time during this process you have a problem meeting this compliance schedule, contact Tucson Water at (520) 791-2650.
My property is served with reclaimed water. Do I need backflow protection?
Yes. Customers receiving reclaimed water must install a reduced pressure backflow prevention assembly (BPA) on all potable water service connections to the property.
Who can install a backflow prevention assembly?
The installation of the backflow prevention assembly may be done by a property owner/occupant (single family residents only), licensed contractor, or a government agency, 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 Tucson Water.
Where should a backflow prevention assembly be located?
Generally, the backflow prevention assembly must be located as close as possible to the potable water service connection, but it must remain on private property.
Who is responsible for the testing and maintenance of the backflow prevention assembly?
It is the responsibility of the customer to ensure that the backflow prevention assembly is in proper operating condition at all times. Backflow prevention assemblies must be tested annually. Tucson Water sends notices to customers reminding them when this test is due. The customer must contact a Tucson Water-approved certified tester to perform the test. If any repair work or maintenance is performed on the assembly, a certified tester must retest the assembly immediately and submit the test results to Tucson Water.
How do I find an approved certified tester?
Tucson Water-approved certified testers are listed in the telephone book under "Backflow Prevention" or "Plumbers." A list of Tucson Water-approved Certified Testers is available here or from the Tucson Water Backflow Prevention Office at (520) 791-2650.
If I have questions about backflow prevention, who do I contact?
Tucson Water
Backflow Prevention Section
P.O. Box 27210
310 W. Alameda
Tucson, AZ 85726-7210
(520) 791-2650