What is the purpose of the hydrostatic valve and how do you release the pressure in it and does this valve need cleaning or other regular maintenance?

Answer 1

A hydrostatic relief valve prevents your swimming pool from wanting to become a 'boat'. If the bottom of the pool is below the level of ground-water, and the pool is emptied, the pool would want to float in the underground water. I have actually seen the deep end of a 40ft gunite pool (with no hydrostatic valve) rise out of the ground (by 18") when the pool was emptied for repairs. A hydrosatic valve would have opened (and allowed the underground water to flow into the pool) when the water pressure beneath the pool became greater than the water pressure in the pool. I am not sure if you can manually test the valve, so check with the supplier/pool builder.

A hydrostatic relief valve is located in the deepest part of your pool. It may be under the maindrain cover or in its own little box on the bottom of the pool. The purpose of the hydrostatic relief valve is to relieve a build up of pressure if it occurs from underneath the pool. If the water were to be removed with a high water table then the pool may float up out of the graound like a barge. You then have a big problem on your hands. The fhydrostatic relief valve will open allowing the ground water to enter the pool to keep the equalibrium and to relieve built up pressure from underneath the pool.

The valve typically does not need any maintenance. However, if the vavle has opened then there is a chance that a tiny particle could get stuck in the seal when the valve closes again. The tiniest particle (which may not even be seen) could allow water to seep out of the pool into the ground.

There's a lot of water in the pool and each gallon of water weighs 8.33 pound. A typical residential pool of 20,000 gallons holds water weighing about 166,600 pounds. A commercial pool of approximately 120,000 gallons has water weighing approx. 1 million pounds.

Removal of this much weight obviously changes a lot of things.

You need to be very careful removing water from a pool. Things to be concerned about are high water table, underground springs, rainy weather, hills behind the pool.

Please write if there are any other questions.

Steve Dunn Certified Pool Instructor Consultant & equipment distributor Commercial Pool Systems, Inc.

FURTHER ANSWER

When you find your pool losing water and don't see any obvious place, it may be the hydrostatic valve has lifted and then not seated properly. The valve needs to be flushed by being lifted momentarily.

I have done this by donning a mask and with fins and weights swum down, removed the grate, and lifted the valve by hand. If you have never seen such a valve find one in a swimming pool store and see how it works.

Also, be sure there is not a lot of trash in the fixture near the valve or again it may not seat. Best to do this with the pump off if the valve is in the drain box or you may get caught by the suction. This can lead to serious death! Paul Delage