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Commonly Used Backflow Prevention Devices
The three most common and effective devices installed to prevent backflow are shown below:

  • Air Gap

    Used mainly on tanks and sinks, it is a gap between the outlet and the basin. 
      - The gap needs to be a minimum two times the supply pipe diameter.

  • Pressure Vacuum Breaker 

    Used mainly on lawn irrigation systems. It has a one way check and a spring loaded air inlet valve that closes when water pressure drops.
    - No backpressure (from fertilizer injection system or water well)
        - 12" above highest sprinkler head
        - Protect from freezing

  • Reduced Pressure (RP) Principle Assemblies
    A reduced pressure principle assembly is a mechanical valve assembly that consists of two internally loaded independently operating check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves.

    It is used for services that have either health hazards or non-health hazards and under conditions of backpressure or backsiphonage. It provides the highest level of protection among the mechanical backflow prevention devices.Cross Connection Control Pro

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