Backflow Prevention

This page provides a summary of the district's cross-connection control requirements. 

Further information is available in our Policies and Procedures Manual - Effective May 1, 2023 (PDF), Section 5.3 Cross Connection Control and Section 2.7 Fire Service Lateral. If you have questions, please contact Cross-Connection Control.

What Is Backflow?

Backflow is the reversal flow of water, liquids, mixtures or substances from a customer's property into Helix's water distribution system. This can happen when there is a reversal in water pressure and a cross connection, a connection between the public water supply and a source of contamination, such as a garden hose in a swimming pool or an irrigation, fire sprinkler, graywater or rainwater harvesting system. Two conditions can cause a reversal in water pressure:

A sudden reduction in Helix's water pressure due to a water main break or vehicle running into a fire hydrant can create suction that draws potential contaminants into Helix's water distribution system

Backflow Back Siphonage

When a customer's water pressure exceeds Helix's water pressure, contaminants can flow into Helix's water distribution system. A well pump or boiler can cause back pressure.

Backflow Back Pressure

An approved, aboveground, Reduced Pressure (RP) backflow prevention assembly is required for commercial, industrial, irrigation, and multiple dwelling water services.

An approved, aboveground Reduced Pressure Detector Assembly (RPDA) backflow prevention assembly is required on all fire service laterals.

Before construction

Manufacturer cut sheets of the proposed RP and/or RPDA backflow assemblies shall be submitted to the District for approval. Only assemblies tested and approved by the University of Southern California Foundation for Cross-Connection Control Hydraulic Research shall be accepted. View List of Approved Backflow Prevention Assemblies.

For a fire service installation, the property owner(s) must complete and record a Fire Service Agreement and submit it with the legal description of the property.

Water Service Backflow Installation & Activation

Reduced Pressure (RP) assemblies shall be installed in accordance with California State Plumbing Code or the local governing authority and per drawing WR-01 of the Water Agencies' Standards. View Water Agencies' Standards.

RP assemblies shall be, at a minimum, the same size as the water meter size and in no case smaller than 3/4-inch. RP assemblies shall be located as close as practical to the meter box.

Fire Service Backflow Installation & Activation

Fire service backflow installation and activationInstallation of an approved reduced pressure detector assembly (RPDA) backflow assembly shall be completed prior to activation of service by Helix Water District:

  • The RPDA assembly shall be installed per drawing WF-05 of the Water Agencies' Standards. View Water Agencies' Standards.
  • The contractor is responsible to forward all requirements to any/all subcontractors performing fire service installations.
  • Construction of the District's lateral must be completed to the end of the District's responsibility before the private line is extended to serve the property.
  • Contractor is to notify the Fire Department and Helix Water District to inspect the fire service pipe system and RPDA from the end of the District's responsibility to the building prior to backfill. Do not cover or bury the pipe prior to inspection.
  • Once the District inspector has signed off on the inspection of the approved backflow assembly, the assembly must be tested by any company on the District's Approved Testers List within 30 days of installation. The certification test report form must be mailed or emailed to the District's Cross-Connection Control Coordinator.
  • The RPDA must have passing test results prior to activation. Helix Water District shall be notified when the fire service is ready to be activated. Only Helix Water District personnel are allowed to operate the District's valve system.


Annual maintenance, testing, and certification are required for RP and RPDA assemblies and shall be done by a District-approved certified backflow assembly tester at the account holder or owner's expense. Copies of maintenance, repair, and certification data shall be mailed or emailed to the District's Cross-Connection Control Coordinator.