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Thread: lots of water behind liner - can't find leak

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    lots of water behind liner - can't find leak

    hello,
    I have a 16'x32' free form shaped inground and recently have had alot of water getting behind liner and i mean alot. in a 48hr period it will take about an hour or more to pump out the water from behind the liner using a small pony pump. the liner is only about 4 years old and i've scoured every inch of it looking for pin holes or anything out of the ordinary. i've tried using die around all return lines, skimmer, main drain, stairs, and seams. nothing. the water level in the pool does not change so the water doesn't seem to be getting away, at least not too quickly. i'm at the point where i need a professional to come in but i seem to be having trouble getting anyone to come out. i've read that there might be a malfunctioning hydrostatic valve in the main drain that might be causing the problem. not sure how to check or repair this valve. does anyone have experience with this or another possible theory?

    thanks.

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    duraleigh's Avatar
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    Re: lots of water behind liner - can't find leak

    Welcome to the forum. It sounds like you might have ground water floating your liner. How do you get the "small pony pump" to extract water behind the liner? I think it's just a matter of doing that constantly until the ground water level recedes
    Dave S.
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    Re: lots of water behind liner - can't find leak

    the pony pump is a small inline pump so i have about a 5ft hose on one end that slides down behind the liner to the bottom in the shallow end and the other hose extension (outlet) i have just shooting back into the pool. the water level does not change once all water is pumped out. I'm in ontario, canada and in the spring time it used to hold ground water after the spring thaw but the last several winters haven't been so bad and i haven't had a problem. also, this summer has been extremely dry for us so i can't see the problem being ground water. fairly certain it's pool water due to the volume.

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    Mod Squad JohnT's Avatar
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    Re: lots of water behind liner - can't find leak

    Sample some of the water you are pumping out and test it for CYA. That way you know for certain whether to keep looking for a leak in the pool or another source.
    TFP Moderator
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    Swampwoman's Avatar
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    Re: lots of water behind liner - can't find leak

    Do you by any chance have a sump beneath your drain that's connected to your system and that you can pump out?
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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    Re: lots of water behind liner - can't find leak

    I've tested the water and it's the same readings as the pool water. as far as i know there's no sump. i just dove down and removed the grate off the main drain to check the hydrostatic valve only to find that it has been capped off. i'm assuming it was done when i had the liner replaced 4-5 years ago. made several calls to different pool guys, can't even get a call back. going to drain the pool below jets and prepare for closing. i'll monitor it for a few days before i close it. hopefully draining it down will shed some light on location of leak.

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    Bluegrassman's Avatar
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    Re: lots of water behind liner - can't find leak

    Quote Originally Posted by JohnT
    Sample some of the water you are pumping out and test it for CYA. That way you know for certain whether to keep looking for a leak in the pool or another source.

    First time I've seen this advice, and it is excellent! One of those things that make you slap your head and say "Why didn't I think of that!!?"
    18x36 Vinyl IG ~27,000 gal, Intelliflo VF Pump, 300# Sand Filter, Polaris 280 w/Pentair Booster Pump, Pentair EasyTouch w/ IC40 SWCG
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    Swampwoman's Avatar
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    Re: lots of water behind liner - can't find leak

    Someone on another current thread used some kind of dye to help find a leak. Have you tried a dye? Sounds like that can be a useful way to find a liner leak.

    Apparently, dye will be "drawn into" the leaking area. If you google it, you will find instructions how to do it.

    The reason. Asked about the sump is because if you're not the owner who constructed it and didn't know it was there, it's possible for the sump to fill up from not being drained. Since you've had trouble with the water table during wet conditions previously, your pool would be a candidate for a sump. (I'm in Michigan, and purchased a home that has one. Fortunately, it's connected to the pump system, and can be pumped out. But we had only discovered that by contacting the original pool builder -- otherwise we'd never have known!) some builders put them in but don't connect them to the system, so you have to pump them out occasionally using some kind of external system.
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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    Re: lots of water behind liner - can't find leak

    Have already used the dye on every seam, connection, and cover in the pool with no sign of a leak. as for the sump, there's no extra plumbing at the equipment that would indicate there is one and there's no other sign of anything (plumbing, switches, plugs, etc) that would show evidence of a sump. as well, i have a copy of the original survey of the pool and equipment layout and there's nothing showing a sump.

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    Swampwoman's Avatar
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    Re: lots of water behind liner - can't find leak

    I guess I'm at a loss for further suggestions short of calling in a pool maintenance company that has a vinyl scanner that finds leaks. Sorry.
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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