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Cross-Connection Control

Purpose

The City and County of San Francisco has a cross-connection control program to protect the City’s drinking water distribution system from contamination caused by backflow. This program was established through the City’s Backflow Prevention Ordinance, adopted in 1984 and revised in 2016.

Who Must Comply?

If your property has a potential cross-connection or hazard (for example, boiler, chemical feed equipment, dedicated irrigation, an interconnected fire sprinkler system, buildings four stories or more in height, or a water supply greater than 40 feet above the water meter), then the requirements of the Backflow Prevention Ordinance apply to you. You are required to install an approved backflow prevention assembly and have it tested at least annually. Failure to test as required may lead to termination of water service, fines, or both.

What Is Backflow?

Under normal conditions, water from the distribution system flows into a consumer’s premises. When backflow occurs, water from the consumer’s premises flows into the distribution system. If that water is contaminated because of activities on the consumer’s premises (for example, addition of rust-inhibiting chemicals to a boiler or use of photo-processing chemicals), the water can carry contaminants into the distribution system, possibly causing illness or even death.

The City’s cross-connection control program is administered by the Water Quality Division of SFPUC and the Environmental Health Branch of the San Francisco Department of Public Health, in coordination with the Plumbing Inspection Division of the Department of Building Inspection.

How Do I Comply?

All potential cross-connections must be protected with an approved backflow prevention assembly.

To be approved for use in San Francisco: 

  1. Approved Backflow Prevention Assemblies List

    An assembly must be on the Approved Backflow Prevention Assemblies list developed by the University of Southern California Foundation for Cross-Connection Control and Hydraulic Research.

  2. Modifications/Installations

    The assembly may not be modified or installed in a manner that differs from the configuration tested and approved.

  3. New Assemblies

    New assemblies must be tested immediately after installation and at least once a year thereafter. After the initial test, Water Quality Division will send you a notice when annual testing is due.

  4. Testing

    All testing must be performed by an Authorized Backflow Prevention Assembly Tester.

Resources for Customers and Contractors

Need help?

To help you comply with San Francisco’s Cross-Connection Control requirements, be sure to check the Consumer Guide to Backflow Prevention and additional program resources listed below. You can also contact the Cross-Connection Control Program at backflow@sfwater.org or (650) 652-3199 between 8 AM and 5 PM.

Last updated: 07/01/2026