Problems with Hydrostatic Valve

Hello everyone. I had a new gunite pool installed last year; first pool I ever owned. They installed a hydrostatic valve because of the very high water table we have in the area. After I had it filled with water I noticed that the pool was leaking water. Turned out that the hydrostatic valve could not close due to debris being stuck in there. Once fixed I had no problems the rest of the summer.

To winterize the pool company pumped out 18" of water. When we opened it this year the pool was down a total of about 24" and I lost another 7" just over the last weekend. I am pretty sure that the valve must have opened at some point and got stuck again. Maybe pumping out 18" was too much and the valve opened up in March during the very wet weather here in the Northeast due to the pressure on the pool.

So what do I do that this won't happen every year. I basically have to have a diver come by, clean out the valve and then have the entire pool refilled. I probably need about 15000 gallons (pool holds about 24000 gallons) Total cost about $750.

Can I plug the hydrostatic valve, or is that not advisable. The pool builder wouldn't "recommend" it, but also said it's an option and should not be a problem while the pool is filled. It would only be a problem if the pool needs to be drained, in which case the valve must be opened again. I understand that the valve is there to prevent the pool from popping out of the ground, but is that really a problem when the pool is filled? On the other hand the valve somewhere did open and got stuck again.

Any advise?

Thanks.