The Principle Operation of a Pressure Vacuum Breaker Backflow Prevention Device Assembly – Air Inlet Valve and Drainage
Because supply pressure keeps the air inlet closed, the PVB shall be installed only where water will not cause damage to the area where the PVB is installed. On startup, the air inlet valve may not close properly because of mechanical issues or insufficient pressure causing water to flow out of the PVB bonnet and into the surrounding area. Siphon conditions and pressure surges will cause the PVB to discharge water as well. The air inlet valve may not seat properly because of dirt or debris located between the air inlet disc and the air inlet seat. The PVB should be installed where spillage is not an issue or objectionable. If the PVB must be installed in an area where water spillage could cause damage, proper drainage shall be provided. The PVB must be installed so that the air inlet valve operates in the vertical position. If the PVB is not installed according to manufacturer’s specification, it may malfunction and not operate properly.