Cross Connection & Backflow Prevention

Western Water is required by state and federal laws to protect its water supplies through its Cross Connection Control and Backflow Prevention Program. This program involves customer site surveys to identify potential hazards and the inspection/testing of new backflow devices. 

As a preventative measure against potential cross-connections, Western Water requires a certified backflow prevention assembly (BPA) to be installed on all non-residential water service connections, all landscape services, and any residential service where an on-site well or booster pumping system is in place. A BPA is also required for any site Western Water considers a potential hazard to the water supply. 

If Western Water requires backflow prevention, the customer is responsible for the installation of the BPA in accordance with Western Water's backflow standards. Additionally, customers are responsible for the annual testing of the BPA. Each year, the customer will receive a testing notice from Western Water along with a list of certified testers. If the BPA is not certified by the customer as required by state and federal laws, Western Water will arrange to have the backflow device tested by an approved certified tester and a non-compliance fee will be added to the customer's account.

Cross Connections

Cross Connections are actual or potential plumbing connections between the public water system and any other system that may introduce a hazard to the water supply. These hazards are considered pollutants (non-health hazards) or contaminants (health hazards). Examples of hazards include but are not limited to, used water, oils, fuel, non-approved water sources, or fertilizers.


Backflow is a reversal of the normal direction of water flow within a water system. Water systems are designed to have higher pressure than the customer’s system to maintain flow in one direction. An undesirable decrease in the main system pressure can create a reverse flow known as a backflow. Backflow can occur during fire suppression efforts or a water main line break. Backflows can also occur if the customer’s plumbing pressure is increased beyond Western Water's system pressure. Examples of this include but are not limited to a pump or elevation.

Additional resources

Approved Backflow Prevention Assemblies

Backflow Prevention Assembly Standard Drawing
Reduced pressure principle backflow preventer for 3/4" through 2" meters (W-0110A)

Backflow Prevention Assembly Test Maintenance Report

Certified Backflow Prevention Assembly Testers

For additional support, email Western Water's Cross Connection and Backflow Prevention team or call 951.789.5115.