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Thread: Plumbing leak, water building behind liner

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    Question Plumbing leak, water building behind liner

    I bought my home last September and I really love the pool, but it has been a constant source of stress and frustration. Not the water chemistry -- thanks to you guys once that was taken care of the first time it has stayed in perfect balance since.

    Last fall there was a lot of rain and my liner floated and shifted. I assumed this was caused by ground water and since it was so near the end of the season when we moved into the house we decided to wait until spring for repairs. This year when we opened we had the liner replaced, but my problems have gotten worse and not better; I have a large build up of water behind the liner, it is behind all of the walls and also under the floor of the pool. When we first filled after the installation of the new liner we noticed a leak. We would lose water very quickly if the plumbing was running but even without it running the water level would drop down to the bottom of the skimmer overnight. At that point there was water behind the liner at the wall of the pool near the skimmer and water under the floor of the pool. The contractor who installed the liner came back and replaced the skimmer faceplate and a gasket and the overnight water loss stopped and the water behind/under the liner dissipated. However, we still had water loss with the pump running. As soon as we realized that we got a robot hoping that we could leave the plumbing turned off and just clean with the robot. After all of the expense of the liner replacement there wasn't a lot of money left for plumbing issues. We didn't run the pump at all for about 10 days, but the water was becoming hazy and we had to turn it on.

    All of this was/is happening simultaneously with heavy spring rains. Right now I have a LOT of water behind the liner, but I'm not sure if it's caused by plumbing issues that existed before the liner was changed, something that the installer screwed up or left undone, or if it's ground water accumulating from the rains.

    This is what I know:
    I lose water when the plumbing is running.
    I don't lose water when the plumbing isn't running.
    There is no loss of prime in the pump, no air bubbles in the pump basket or the returns. The prime holds whether the pump is running or not.
    There is absolutely no water at all coming out of one of the returns -- the one on the wall with the most water buildup behind the liner. There was water discharge there last year.
    We have had a LOT of rain.
    None of the water seems to be dissipating.
    The water behind/under the liner gets worse when we run the pump. Consequently, the pump is on very seldomly.
    If the ground isn't wet from rain I can walk in the grass at the edge of the pool without getting my feet wet, making the full circumference, even after I've been running the pump. The "lost" water doesn't seem to make the ground around the outside of the pool soft or wet.
    We ran the plumbing a lot last year and, to the very best of my memory, only had water accumulate under the liner after we had the heavy rain. (Please keep in mind that I was completely new to pool ownership at that time and might not have noticed or made the connection, also the rains came soon after we moved in)

    So... When the liner is changed are the returns disconnected? Could the installer have left something undone? Can leaks in the return lines cause water between the liner and the shell? What can I do CHEAPLY to get rid of the water and make sure it doesn't come back?

    If anyone can offer any help or insight I'd sure appreciate it.
    10,500 gal inground pool with vinyl liner. sand filter, TF100 test kit.

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    Casey's Avatar
    Join Date
    Apr 2007
    SW PA

    Re: Plumbing leak, water building behind liner

    Hi Granny. Before we get to far in, May I ask that you add your location to your profile? Also, I want to congratulate you on your fine job of running this pool with a TF100 test kit! That kit is pretty great!

    Okay, on to ground water. I'm in PA and we have been hammered with rain! It has been a very wet spring and many others have had a lot of floating liners this year so you are not alone. What I would suggest for the ground water is well points. What those are is holes dug into the ground around the perimeter of the pool. You can fill them with large diameter PVC and gravel and sink a sump pump into them and when they fill with water, you turn the pumps on and drain the water and it basically pulls all the water away from your pool.

    Now, onto the issue and that is your leak. It sounds like you definitely have one when you're pump is running and since you think you are losing water and it's going behind your liner, I would call the installers back and have them double check every return and *hole* cut into the liner and reseal them. If you can, see if you can get in and check to see if your eyeballs are tight on the wall and such. If you can't tell, maybe a leak detection is in order to help pin point it. I would hold off and see what others have to say on this as we have very knowledgable members here at TFP.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

  3. Back To Top    #3

    In the Industry

    Join Date
    Nov 2011

    Re: Plumbing leak, water building behind liner

    Plumb from the filter pad back to the pool plug the returns in the pool and see if you lose water. Suspect that you have a broken return under the deck. You could also pressure test the line
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
    Certified in Hydraulics

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