Hydrostatic pressure relief valve

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 in the pool floor.

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 the 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.