Hydrostatic pressure relief valve. For use in pools where the water table is higher than the pool floor. MUST be installed in pools that are near lakes, rivers, the beach., and areas susceptible to flooding. They should be positioned in a gravel (aggregate) bed below the pool floor. - see notes below.
Hydrostatic pressure relief valves are required to be installed in the floor or drain sump of in-ground pools where the surrounding water table is above the base of the pool. It opens when there is pressure from ground water under the pool. It allows the ground water to enter the pool. This prevents damage to the pool by the pressuere of the surrounding water.
The build up of ground water can exert surprising amounts of hydraulic pressure on structures such as swimming pools. It is not uncommon for vinyl liner to be pushed several feet out of the ground or even fractured by ground water pressure. Empty concrete pools can rise out of the ground causing extensive damage even if the movement is only a few millimetres. One of tshe best ways of avoiding these costly mishaps is the installation of a hydrostatic valve in the bottom of the pool which will open when the pressure of the ground water exceeds a set point and allow it to flow into the pool. Some dirty water in the pool or a slight overflow is then the only result of the excess pressure.
Valve stem
