Backflow Requirements and Types

The City of Bellingham requires a backflow preventer on any cross-connection or potential cross-connection. The backflow preventer may be required on the water service 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, the water customer is 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 (PVB)
  • Atmospheric vacuum breakers (AVB)

What type do you need?

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 Bellingham accepts Air Gaps(AG) and Reduce Pressure Backflow Assemblies (RPBA) as protection for different types of high hazards including the following:

  • Car washes
  • Commercial laundries and dry cleaners
  • Premises where both reclaimed water and potable water are provided
  • Film processing facilities
  • Food processing plants
  • Hospitals, medical centers, nursing homes, veterinary, medical and dental clinics, and blood plasma centers
  • Customers with separate irrigation systems using the City’s water supply
  • Chemical plants
  • Beverage bottling plants
  • Laboratories
  • Metal plating industries
  • Mortuaries
  • Petroleum processing or storage plants
  • Piers and docks
  • Wastewater lift stations and pumping stations
  • Wastewater treatment plants

Low Hazards: For low hazards including fire systems and irrigation systems, City of Bellingham accepts double check detector and double check valve assemblies, pressure vacuum breaker assemblies and atmospheric vacuum breakers as types of protection.

Backflow Preventer Inspection

City of Bellingham 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 service. A copy of the test report must be provided to the City of Bellingham.

 Backflow 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 Bellingham. 

More Information

For answers to specific cross-connection control questions, contact the Cross-Connection Control Specialists at the Operations Division of the Public Works Departmentor email