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Thread: Hydrostatic relief valve

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    Hydrostatic relief valve

    I recently posted a blurb about a in ground pool leak on april 29. I have a main drain in the pool and wasa wondering if there is a possibility that the drain has a hydrostatic relief valve that may have failed or somehow let the water escape from my pool over the winter. What can anyone tell me about a these valves and how they operate or how they might malfunction. Thanks
    London, Ontario, Canada
    16' x 32' IG steel wall, vinyl lined straight back kidney, 5' deep
    Aquarite SWG, pentair clean and clear cartridge filter, 3/4hp whisperflo pump
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    spishex's Avatar
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    Oct 2008
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    Hillsborough, NC
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    Re: Hydrostatic relief valve

    They're check valves that only swing open upward (toward the pool), so there has to be more pressure on them from the bottom than the top. I've never seen one leak, but I'm sure it's possible. You'd have to use some dye down at the main drain to see.

    How big is the leak?

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Hydrostatic relief valve

    A hydrostatic relief valve is sometimes installed as part of a main drain. It allows ground water to enter the pool when the pool water level is lower than the ground water level. This prevents the pool from floating out of the ground, but tends to mess up the pool water.

    These valves use a float system to detect when there is more water pressure below the pool than there is in the pool. The most likely failure is when they open correctly, ie when there is excess ground water pressure, and debris is washed into the pool along with the ground water. The debris can then block the valve from closing completely. Other kinds of failure are also possible, but not nearly as likely.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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