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How an AVB Works

This type of backflow prevention device is designed to protect potable water supplies from contamination due to back siphonage. When water flows normally through the AVB, an internal poppet or float is pushed up by water pressure, allowing the system to function normally. However, if the water pressure drops, a vacuum can form in the pipes, pulling contaminated water back into the clean water supply. When water flows in reverse due to a drop in pressure, an AVB backflow preventer will activate, opening the air inlet, breaking the vacuum, and preventing backflow. 

Atmospheric Vacuum Breaker FAQs

How does an AVB prevent backflow?

An Atmospheric Vacuum Breaker prevents backflow by introducing air into the system when a pressure drop occurs, breaking the vacuum that could siphon contaminated water back into the clean supply. This is effective against back siphonage but does not protect against back pressure.

What is the difference between an Atmospheric Vacuum Breaker and a Pressure Vacuum Breaker?

AVBs and Pressure Vacuum Breakers (PVB) both prevent back siphonage, but differ in design. A PVB includes a spring-loaded check valve and an air inlet valve, allowing it to handle continuous pressure and protect an entire system from one installation point.

How often should an AVB be replaced?

An atmospheric backflow preventer may need to be replaced every 5 to 10 years, depending on usage frequency and exposure to harsh weather conditions. Regular inspections and maintenance can help extend its lifespan, but if you notice leaks, corrosion, or failure to seal properly, it should be replaced immediately.