A cross connection is a connection between a drinking water supply and a source of pollution or contamination. The undesirable reversal of flow that may allow entry of pollutants and contaminants into the drinking water supply is called "backflow."


To ensure drinking water supplies are protected from contamination, Cross Connection Control Program staff inspect commercial facilities, industrial buildings, irrigation systems, and water distribution systems for proper installation and maintenance of backflow prevention assemblies. Additionally, staff monitor the installation, repair, and annual testing of over 16,000 backflow prevention assemblies installed on distribution systems operated by public water purveyors throughout the County.

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Backflow Device Test Apps links:

Information for Backflow Testers:

General Information and Public Resources:


Staff Specialist:
Holly Sinclair
805 654-2436
Ron Ventura
805 654-2816