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. 

Requirements:

• 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.

Requirements:

•     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