hydrostatic valve leak

[millpool]

My pool was perfectly filled one week. The next week it was overflowing because of water pressure under the hydrostatic valve. Six days later there was 2.5 feet of water in the deep end. Apparently the valve was stuck in the open position. This has happened twice before. Can anyone recommend how to fix this one and for all? Thanks

[Poconos]

Welcome to the forum.
Are you saying the ground water at one time was higher than the pool water thus opening the valve? Then the valve stuck open and the pool drained? I may be totally confused and off base but I thought these valves were to prevent the pool from floating if the ground water level rose too high. If this is true then I question how the ground water level changed so fast. I'm not at all familiar with these things so I won't be any help but I am curious about the scenario. Sorry.
Al

[sunofthebeach]

My hydrostatic valves don't open and close by themselves.

If I were ever to drain my pool I would unscrew the valves so I would let ground water in, so the pool would not pop up.

[JohnT]

My pool was perfectly filled one week. The next week it was overflowing because of water pressure under the hydrostatic valve. Six days later there was 2.5 feet of water in the deep end. Apparently the valve was stuck in the open position. This has happened twice before. Can anyone recommend how to fix this one and for all? Thanks

If your valve opened while the pool was full of water, then there was more pressure from groundwater outside the pool than from the pool water inside the pool. A very unusual situation. Is the pool located in a hillside or at the bottom of hill? On first glance, it this appears to be a serious engineering issue.

[imfignewton]

The hydrostatic valve did its job but it sounds like the pool builder did not put the slotted pipe at the bottom of the valve. The valve is poping up like it is suppose to do but gravel is floating up and sticking in the valve leaving it open. When you see the water level dropping dive down and remove the main drain cover and check the hydrostatic valve, if there is gravel stuck in it, pick it out and the valve will reset itself (turn the pump off first).