Backflow Requirements & Types

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The City of Bainbridge requires a backflow preventer on any cross connection or potential cross connection. The backflow preventer may be required on the water services line, within the building, or in both locations. The backflow preventer you choose must be listed on the Washington State Department of Health's Approved Backflow Prevention Assembly List. Assemblies not currently listed must have been listed at the time of the original installation.

After the initial inspection and testing of all newly installed backflow preventers, water customers are required to have the backflow preventer tested on an annual basis by a Certified Backflow Assembly Tester (BAT).

Backflow Preventer Types

  • Air Gaps (AG)
  • Reduced Pressure Backflow Assemblies (RPBA)
  • Double Check Valve Assemblies (DCVA)
  • Pressure Vacuum Breaker Assemblies (PVBA)
  • Spill Resistant Pressure Vacuum Breaker Assembly (SVBA)
  • Atmospheric Vacuum Breakers (AVB)
  • Double Check Detector Assembly (DCDA)
  • Reduced Pressure Detector Assembly (RPDA)

What Type do You Need?

Backflow Standard Drawings: Bainbridge Island Municipal Code

  • 10-160 (PDF) - Double Check Detector Assembly for fire sprinkler systems 2 inches or larger.
  • 10-161 (PDF) - Double Check Valve Assembly 2 inches and smaller.
  • 10-162 (PDF) - Underground with upstream meter Double Check Valve Assembly 2.5 inches and larger.
  • 10-163 (PDF) - Reduced Pressure Backflow Assembly 2 inches and smaller.
  • 10-164 (PDF) - Reduced Pressure Detector Assembly Fire Sprinkler System 2 inches and larger.
  • 10-165 (PFD) - Above ground with upstream meter Reduced Pressure Backflow Assembly 2.5 inches and larger.
  • 10-166 (PDF) - Pressure Vacuum Breaker Assembly for 2 inches and smaller.
  • 10-167 (PDF) - Double Check Valve Assembly for three units or greater - 2 inches and smaller underground.

The level of protection required is determined by the degree of hazard as outlined in the Washington Administrative Code ( WAC ) for specific types of use. The general guidelines include:

High Hazards: City of Bainbridge Island accepts Air Gaps (AG) and Reduce Pressure Backflow Assemblies (RPBA ) as protection for different types of hazards. See hazards list (PDF).

Backflow Preventer Inspection

The City of Bainbridge Island inspects backflow assemblies upon installation and conducts periodic re-inspections on all existing assemblies. New assemblies must be tested by a State of Washington certified backflow assembly tester prior to putting into services. A copy of the test report must be provided to the City of Bainbridge Island.

Flow Preventer Annual Testing

All backflow preventers must be tested annually and after repair, relocation, or replacement by a State of Washington Certified Backflow Assembly Tester (BAT). A copy of the test report must be provided to the City of Bainbridge Island.


See the Regulations & Forms webpage to locate required forms for both the City sponsored backflow testing program and the independent testing process.

More Information

For answers to specific cross-connection control questions, please contact the cross connection control specialists at Operations and Maintenance by email or phone (206.842.1212).