ATMOSPHERIC VACUUM BREAKER. A backflow prevention device which introduces air into piping system to prevent back siphonage. Cannot be under constant pressure (constant pressure is defined as "more than 12 hours") The AVB must be installed at least 6" higher than all down stream piping and the highest downstream outlet. No backpressure may exist. No shut off valves may exist downstream of the AVB.

The lowest grade of backflow prevention equipment. When the pressure drops, the AVB allows air to enter the line to prevent back siphonage of contaminated water into the water supply. AVBs do not protect against back pressure. Back to glossary index.

AVB (Acappella Vocal Band, or All Vocal Band), is a spin-off group formed from the former backup singers of the Contemporary Christian act Acappella. While Acappella maintained a more traditional adult-oriented vocal style, AVB's music was aimed at a younger audience. Their sound is similar to Take 6, Boyz II Men, and Tony!