Reduce Pressure Principle (RP)
Backflow Prevention Assembly
An assembly containing two independently acting approved check valves together with a hydraulically operating, mechanically independent pressure differential relief valve located between the check valves and at the same time below the first check valve.

Double Check Valve (DC)
Backflow Prevention Assembly
An assembly composed of two independently acting, approved check valves, including tightly closing resilient seated shutoff valves attached at each end and fitted with properly located resilient seated test cocks.

Pressure Vacuum Breaker
Backsiphonage Prevention Assembly (PVB)
An assembly containing an independently operating internally loaded check valve and an independently operating loaded air inlet valve located on the discharge side of the check valve. Equipped with properly located resilient seated test cocks and tightly closing resilient seated shutoff valves attached at each end of the assembly.

Atmospheric Vacuum Breaker
Backsiphonage Prevention Assembly (AVB)
A non pressure type vacuum breaker assembly containing an air inlet, a check seat and an air inlet port. When water flows it causes the valve to close. When there is no water flow the air inlet valve falls and form a check valve against back siphonage. These devices are constantly installed improperly. They are not suppose to have constant water pressure. An example is a sprinkler system. They are suppose to have a master valve before it so there is not water pressure to it when the sprinkler system is turned off.

Which device for what application?

There are two different degrees of hazard associated with backflow.

• Non-health or pollution

  The impairment of the quality of the water to a degree which does not create a hazard to the public health but does adversely and unreasonably affect the aesthetic qualities of such waters for domestic use. The backflow from a candy factory putting chocolate in the city water from a vat would be an example.

• Health or contamination

  The impairment of the quality of the water which creates an actual hazard to the public health through poisoning or through the spread of disease by sewage, industrial fluids, waste, etc. You are filling your car radiator with the hose stuck in it. A fire several blocks away causes a siphonage when they start pumping water sucking the anti-freeze right out of you radiator into the city water is an example.

Which devices are rated for what type of backflow?

• AVB (Atmospheric Vacuum Breaker)

  It is designed to protect against a non-health or a health hazard under a backsiphonage condition only.

• PVB (Pressure Vacuum Breaker)

  It is designed to protect against a non-health or a health hazard under a backsiphonage condition only.

• DC (Double Check)

  This assembly shall only be used to protect against anon-health hazard.

• RP (Reduced Pressure Principle)

  This assembly is designed to protect against a non-health or a health hazard. It can not be used for backflow protection of sewage or reclaimed water.

What does all this mean

We are here to answer any questions you have about backflow. Irrigation systems should have a double check properly installed on them. We believe the time is coming when you will see preventers installed on all homes. The cases are numerous of people getting sick and even dying due to backflow accidents. What is really scary is when you see that some hospitals have out of date or non working preventers installed at their facilities. Dental offices without proper preventers installed. The cities are now implementing programs to get everyone up to code. Your local city building inspection or plumbing department can inform you on local codes.