Backflow prevention

Backflbackflow imageow devices prevent used water from reentering the District’s potable water supply in the event of a malfunction in a consumer’s pressure equipment or a sudden drop in pressure in EBMUD’s water system.

Examples of backflow conditions include backsiphonage and back pressure.

  • Backsiphonage is caused by a reduced pressure in supply piping. Backsiphonage can be caused by undersized piping, a line repair of a break that is lower than a service point, reduced main pressure due to high withdrawal rates such as firefighting or flushing water mains, or a reduced supply pressure on the suction side of a booster pump.
  • Backpressure may occur when the potable supply piping is connected to a system or fixture which exceeds the operating pressure of the supply piping. Higher pressure can be caused by booster pumps, boilers, pressure vessels, or elevated piping in places such as high-rise buildings or tanks. If these connections are not properly protected, potable and non-potable water or liquids can be forced into the potable supply system.

Backflow prevention

The California Code of Regulations, Title 17, mandates water purveyors, such as EBMUD, to administer a cross-connection control prevention program, which helps keep potable water from contaminant and pollutant exposure.

As part of EBMUD’s program, the District’s backflow inspectors are required to conduct site inspections to determine if a backflow prevention device is required as a result of an actual or potential cross-connection hazard on a customer’s plumbing system.

Please let EBMUD know of any situation that may require a backflow device. Sometimes conditions on properties change that may require a backflow device, such as treating a boiler with additives or installing a well with a pump.

For safety purposes, please inform the Backflow Section of any changes that might require backflow protection.


If you are required to install a backflow assembly, please follow these guidelines:

  • Follow the appropriate standard drawing.
  • It is the customer’s responsibility to install, test, maintain, and assume all costs for an approved backflow assembly at the service connection.
  • The customer has 30 days to complete installation and testing of a backflow prevention assembly (check the due date on Notice of Requirements form).
  • Local city and county permits may be required. Please contact your local city/county permitting office.
  • If the water will be used for consumption, the assembly must be lead-free. You will find a list of all backflow prevention devices approved for use in the State of California at the following link:  https://fccchr.usc.edu/list.html

After installation:

A test must be performed by a tester on EBMUD’s Certified Backflow Testers List. Send the completed test form by mail within 30 days of notification to:

EBMUD
Backflow Prevention Section
MS 47, PO Box 24055
Oakland, CA 94623

  • Call and schedule a follow up inspection by an EBMUD Backflow Inspector to verify that assembly is correctly installed.
  • When a “Notice of Correction” or “Notice of Requirement” is issued, failure to install or correct an installation and then test a backflow assembly may result in service interruption or termination.

Residential dual domestic and fire services

A single (one water meter with one kitchen) domestic dual service requires a UL/FM approved single check valve. If there is an auxiliary water supply (a cistern, a well, a creek, on or at the border of the property), it will require an inspection to determine what type of backflow prevention is needed.
EBMUD will conduct an inspection after the customer’s water meter fees are paid. As a reference, below are two typical single residential installation drawings.

Typical residential installation

Typical residential installation

Typical residential installation

Typical residential installation

Dedicated fire services

An EBMUD Backflow / Cross-Connection Control Specialist will conduct a survey of the site to determine if conditions exist that require installation of an approved assembly after the meter.

All new fire-services require a flush of the underground piping prior to service activation. The Backflow Section must witness the flush. Please schedule the local Fire Marshall/Fire Inspector before calling EBMUD for a fire flush appointment. The Backflow Section requires at least a 48 hour notice prior to scheduling the flush. An underground fire service flush will not be performed until an appropriate backflow assembly has been installed.

During the flush, regulations regarding discharging chlorinated water into storm drains must be observed.

Chlorinated Water Discharge Best Management Practices

Contact us 

Please call us at 510-287-0874.