What is an atmospheric vacuum breaker assembly (AVB)?
An AVB can be used to protect against backsiphonage where it is not subjected to backpressures. The most commonly used atmospheric anti-siphon vacuum breakers incorporate an atmospheric vent in combination with a check valve. Its operation depends on a supply of potable water to seal off the atmospheric vent, admitting the water to downstream equipment. If a negative pressure develops in the supply line, the loss of pressure permits the check valve to drop sealing the orifice while at the same time the vent opens admitting air to the system to break the vacuum. It must be installed on the discharge side of the last shut-off valve and must be installed 6″ above highest outlet. Typical installations include hose bibbs, chemical vats, X-ray tanks, turf irrigation systems, and laboratory sinks.
