Installation Requirements + Guidelines

Assemblies 2" and smaller

Install with a minimum of 6-inch clearance in all directions around the assembly.

Assemblies 2 1/2" and larger

Install with a minimum of 12" (inch) clearance in all directions around the assembly and a minimum of 24" (inches) clearance in front of the assembly, where testing and repair are performed.

Pressure Vacuum Breaker (PVB)

Must meet the additional requirements of 12" (inches) above the highest point of water use downstream of the backflow preventer.


  • Backflow Prevention Assembly (BPA) installed in the WaterOne service area must be on the "List of Approved Backflow Prevention Assemblies," which is published by the Foundation for Cross-Connection Control and Hydraulic Research from the University of Southern California.
  • BPA must be installed per WaterOne requirements for Cross Connection Control.
  • BPA must be inspected for compliance with installation criteria including correct orientation.
  • BPA must be tested at the time of installation by a qualified (certified) tester, then annually thereafter. Test results must be recorded on WaterOne's test report form (PDF) and returned to Cross-Connection Control staff prior to final approval of the installation.
  • BPA should be re-tested anytime water service to the assembly is disrupted.
  • Whenever a BPA is installed that could create a closed water system, a solution for thermal expansion needs to be considered.
  • In the event there is a conflict between WaterOne's requirements and municipal plumbing codes, the more stringent requirement will prevail.
  • Municipal plumbing codes have been modified to include a maximum installation height for BPA without providing special access to the BPA for testing and repair.
  • A reduced pressure assembly (RPA) is designed to discharge water. The amount of water that may be discharged can vary from:
    • "nuisance spitting" at the RPA relief port during water pressure fluctuations
    • major water discharge in the event the RPA needs repair
    • in response to an actual backflow situation.
  • Water meters, as part of detector assemblies, shall read in gallons per minute (GPM).