Backflow Prevention

Once water enters your sprinkler system it is no longer potable (drinking) water as it can become contaminated with pesticides, herbicides, fertilizers and animal waste. These contaminants can enter the sprinkler system and water supply through broken sprinkler lines or heads, fall sprinkler blow out, or a high demand event (such as a broken water main) on the public water system. If a backflow assembly is absent, not installed properly, or is not functioning properly, contaminated water from the sprinkler system can be forced back into your home’s water supply and/or the public water system. To protect water quality in your home and the public water supply, your sprinkler system is required to have a properly functioning backflow assembly. A backflow assembly is a mechanical valve designed to prevent the reverse flow of water from a point of hazard (sprinkler system) to the public water supply. Because backflow assemblies are mechanical devices, they must be tested annually to verify they are working properly. Backflow assemblies can fail over time or may become damaged from winter freezing or improper blowout in the fall. A properly functioning backflow assembly prevents these potentially hazardous substances from entering the water supply.

To ensure that the water system is properly protected and that all system users receive safe drinking water, the Liberty Lake Sewer and Water District (LLSWD) requires that all customers, residential, multifamily and commercial, test their backflow assemblies annually. Annual backflow assembly testing is required to ensure proper function of the assembly and protection of the water system. Testing must be performed by a Washington State certified Backflow Assembly Tester and must be completed by June 30 annually. If repairs are required, they usually can be completed at the time of the backflow test. After a successful test is completed, testers submit a test report to the LLSWD. The test reports are LLSWD’s method of confirming that backflow assemblies have been maintained and function properly so the system is safe for all users.

The LLSWD is required to have a Cross-Connection Control Program in accordance with Washington Administrative Code (WAC) Chapter 246-290-490. The purpose of the LLSWD’s Cross-Connection Control Program is to protect the public water system from contamination via cross-connections.

For more information, please visit the LLSWD’s Cross-Connection Control Program webpage for requirements, additional education resources, and a list of some local, Washington State certified Backflow Assembly Testers at If you have questions, please call LLSWD at (509) 922-5443 or email us at

Cross Connection Control

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