Backflow Prevention

Backflow prevention devices

Backflow prevention devices stop our water supply from possible contamination by residential and commercial sources. In the event of a malfunction in consumer pressure equipment and/or a sudden drop in pressure in the District system, these devices prevent water that has already left the District system from being siphoned back in, guarding the system from possible pollution.

Get a backflow prevention device

Backflow prevention devices are supplied and installed by the District and paid for by the customer. District inspectors test the devices annually to make sure they're operating properly, and repair or replace any failed or improperly functioning device. 

For information on pricing on devices and installation, please call Customer Service at (925) 688-8044. Maintenance costs are listed on our current rates page.

How to know if you need one

We have an inspection program to identify water sources and situations that require backflow prevention devices. For residential property, it is important for owners to alert the District if any changes are made, such as digging a new well. For commercial property, the District reviews the use of each new tenant. If the current backflow is not up to District code, the correction must be made before water service is permitted. Cost for the device is covered by either the tenant or the property owner.

All secondary sources of water, such as wells or plumbing systems that are exposed to potential contamination or poorer quality water, require a backflow prevention device. 

Examples where protective devices (such as double check valve assemblies) are required:

  • Residences with an additional water supply (such as a well or the canal)
  • Swimming pools or irrigation systems supplied by a separate water service or without a satisfactory air gap or anti-siphon device on the inlet line
  • Buildings with internal booster pumps systems
  • Buildings three stories or more
  • Premises where there are hazardous materials under pressure or where toxic materials are used (hospitals, mortuaries, etc.)
  • Sewage pumping or treatment plants