Patent ID: 8056156

Claim:
A vacuum relief unit for venting air into a pool pumping system when a pressure level within the pool pumping system drops below a first pressure level limit, the vacuum relief unit comprising: an air chamber that is closed to contain chamber air, sealed from the pool pumping system by a chamber air venting means, and sealed from atmospheric air by an atmospheric air venting means when water is flowing through the pool pumping system; the chamber air venting means being biased to seal the air chamber from the pool pumping system when the pressure level in the pool pumping system is at or above the first pressure level limit and being adapted to vent the chamber air from the air chamber into the pool pumping system when the pressure level in the pool pumping system drops below the first pressure level limit; the atmospheric air venting means being biased to seal the air chamber from atmospheric air surrounding the vacuum relief unit when the pressure level in the air chamber is at or above a second pressure level limit that is lower than the first pressure level limit and being adapted to vent atmospheric air into the air chamber when the pressure level within the air chamber drops below the second pressure level limit and is therefore lower than the first pressure level limit; and means for delaying operation of the atmospheric air venting means when the pressure within the air chamber is no longer below the second pressure level limit so that atmospheric air continues to be vented into the air chamber by the atmospheric air venting means after the pressure in the air chamber is no longer below the second pressure level limit.