The Principle Operation of an Atmospheric Vacuum Breaker Backflow Prevention Device – No-Water Out of the Box
No Water – The AVB out of the box. The float disc/poppet is in the downward position and the air inlet port is open. The AVB float disc in a downward position acts as a closed check valve and an open-air inlet valve. The AVB float disc when in an upward position, acts as an open check valve and a closed air inlet valve. The float disc is not spring loaded. Atmospheric pressure keeps the float disc in the downward position and supply pressure keeps the float disc in an upward position. In this exploded view of a typical AVB, note the location of the one-piece construction float disc/poppet.
