WMWD Cross Connection and Backflow Prevention

Western Municipal Water District (Western) has an advanced Water Quality department that is committed to delivering quality water to the service meter of its valued customers. A vital part of Western Water Quality program is the Cross Connection Control/ Backflow Program.

Cross Connections

Cross Connections are actual or potential plumbing connection between the public water system and any other system that may introduce a hazard into the water supply. These hazards are considered either a pollutant (non-health hazard) or contaminant (health hazard). Examples of hazards are, but not limited to: used water, oils, fuel, non-approved water source or fertilizers.


Backflow is a reversal to the normal water flows direction within a water system. Water systems are designed to have higher pressure than the customer’s system to maintain flow in one direction. If an undesirable decrease in the main system pressure occurs, this can create a reverse flow- backflow situation. This can occur with high demand from firefighting efforts or a water main line break. This can also occur if the customer’s plumbing pressure is increased above the Western's water systems pressure. Examples of this are, but not limited to: a pump or elevation.


Western is required by federal and state laws to protect their water supplies and maintain a Cross Connection Control/ Backflow Program. This program involves surveys of customer sites to verify potential hazards as well as inspection/testing of new backflow devices. As a preventative measure against potential cross-connections, Western requires a certified backflow prevention assembly (BPA) 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 or any site Western considers a hazard to the water supply. If backflow prevention is required by Western, the device will need to be installed according to Western requirements. The installed backflow devices must be tested annually. This is the customer’s responsibility. Each year the customer will receive testing notice from Western as well as a list of certified testers. If the BPA is not certified by the customer as required by federal and state laws, Western will have the backflow tested by an approved certified tester. A non-compliance fee will be added to the customer's account.

The Cross Connection / Backflow Department may be contacted at (951) 789-5115 or via E-mail at westernbackflow@wmwd.com


Cross Connection/ Backflow Forms

Approved List of Testers
Backflow Standard Drawing
List of Approved Backflow Prevention Assemblies
WMWD Backflow Test Form