Performance Requirements for Backflow Preventer with an Intermediate Atmospheric Vent - ANSI Approved (September, 2009)
The devices covered by this standard are those which have functional capabilities for preventing both back-siphonage and back pressure and which can operate under continuous or intermittent pressure conditions. These devices have two (2) independently operating check valves separated by an intermediate chamber with a means for automatically venting it to the atmosphere and can be installed in the horizontal, vertical up or vertical down orientations. The check valves are force loaded to a normally closed position and the venting means is force loaded to a normally open position.
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