Atmospheric Vacuum Breakers (AVB)

Boasting the simplest backflow preventer design, Atmospheric Vacuum Breakers (AVBs) are also the least expensive—but only if you have less than six control valves. Though atmospheric vacuum breakers aren’t designed as a whole-system backflow prevention valve, they’re still premium quality, highly efficient devices that stand as a paramount solution for preventing backflow contamination, thereby ensuring the utmost purity and safety of your water supply.

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.

Where should an AVB be installed in an irrigation system?

An Atmospheric Vacuum Breaker should be installed downstream of each zone valve and at least 6 inches above the highest sprinkler head or drip emitter in that zone. Proper placement prevents backflow and ensures the AVB functions correctly to protect your water supply.

How does an AVB affect water pressure?

An AVB causes a small amount of pressure loss as water passes through it, but it’s usually minimal. This slight reduction is due to the internal components that allow air to enter and prevent backflow. In most irrigation systems, this pressure drop isn’t noticeable, but it’s still important to account for it when sizing zones, especially in low-pressure systems.

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.

Atmospheric Vacuum Breakers (AVB)

How an AVB Works

Atmospheric Vacuum Breaker FAQs

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Atmospheric Vacuum Breakers (AVB)

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How an AVB Works

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