• Backpressure occurs when the pressure at the point of use is higher than the water distribution system’s pressure. The pressure differential can reverse the flow of non-potable water into the City’s drinking water supply. Sources of backpressure include booster pumps, boilers, elevated piping, pressurized substances, and interconnections with auxiliary systems.

• Back-siphonage occurs from negative pressure in water lines. Conditions that create back-siphonage include high velocities in pipes from maintenance, line breaks, and firefighting. Negative pressure in the supply creates a vacuum, and this allows non-potable liquids to enter the City’s drinking water supply via back-siphonage.

It is the City’s responsibility to protect customers from contaminated water. The backflow prevention assembly is the key to preventing unwanted substances from entering our distribution system. In case of a drop in the City’s water pressure, the backflow device will stop water from flowing in reverse and possibly contaminating the drinking water supply. 

American Backflow Prevention Association Message - YouTube Video

 Backflow occurs under back-siphonage or backpressure  conditions.

• Back-siphonage occurs from negative pressure in water lines. Conditions that create back-siphonage include high velocities in pipes from maintenance, line breaks, and firefighting. Negative pressure in the supply creates a vacuum, and this allows non-potable liquids to enter the City’s drinking water supply via back-siphonage.
• Backpressure occurs when the pressure at the point of use is higher than the water distribution system’s pressure. The pressure differential can reverse the flow of non-potable water into the City’s drinking water supply. Sources of backpressure include booster pumps, boilers, elevated piping, pressurized substances, and interconnections with auxiliary systems.

A cross-connection is any direct or indirect connection between a potable water supply and a non-potable source. Non-potable sources include liquids, solids, or gases that could contaminate the potable water supply through backflow. Examples of “cross-connections” are post-mix soda machines, soap aspirators, chemical injectors, cooling towers, boilers, and chillers connected to the potable water supply.

 A backflow prevention device prevents the entry of unwanted substances into the City’s drinking water supply. If the City’s water pressure drops, the backflow prevention device stops water from flowing in reverse in order to prevent contamination of the City’s drinking water supply.

For approved uses and specifications regarding backflow prevention devices, make sure to refer to the City of Avondale Municipal Code and Avondale's Supplement to Maricopa Association of Governments' Uniform Specifications and Standard Details For Public Works Construction (Avondale’s MAG Standard Detail).

Backflow prevention devices are installed to protect your drinking water from potential sources of contamination. The only way to ensure that they are working properly is to have a “Certified Backflow Prevention Assembly Tester” test them. The Uniform Plumbing Code Section 603 and the Arizona Administrative Code (Title 18, Chapter 4) both require annual testing of installed backflow prevention devices. The City of Avondale Public Works Department will notify City water customers when their annual test results become due. 

Only a “Certified Backflow Prevention Assembly Tester” is permitted to test any backflow prevention devices. The City of Avondale compiles an Approved Tester List for City water customers to select their testers. Customers are required to coordinate the annual testing of their backflow prevention devices with a certified tester approved by the City of Avondale. City of Avondale Public Works staff files the test results and then creates a schedule for the following year’s test.

The following is a list of requirements and the form:

• Current tester certification for all testers employed by your company
• Proof of current liability insurance
• Current test equipment calibration for all test gauges being used in the City
• Phone number

Please attach all requested items and email them to: backflow@avondaleaz.gov 

The City of Avondale will refuse the submission of test reports from testing companies that fail to provide items from the above list. Failure to maintain the required documentation updated will result in the tester and/or company removal from the list of recognized testers.

Public Works Department: (623) 333-4400 

Fax: (623) 333-0440 

backflow@avondaleaz.gov