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Thread: Ground Water - Floating Liner - Behind the Liner Drain

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    J_L_D's Avatar
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    Jul 2010
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    Madison, MS
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    39

    Ground Water - Floating Liner - Behind the Liner Drain

    Hi,
    Last week, the pool was drained, prepped, and new liner installed. Vacuum fan ran for 24 hours while filling the pool. All good. Then massive rains came and this morning there is water under the liner. It's not what I would call major, but clearly evident at floor and wall intersections where it is spongy. The whole liner seemed to be sort of bowl shaped in the deep end before the vacuum and water weight formed it to the walls and floor (Is this normal?), and now the tight form has gone back to more of a curved shape where there is water under it. I guess the liner is a tight (stretched) fit, and maybe that's why it's not wrinkled at this point.

    At this point the steps have been cut in, but nothing else like returns or skimmers. I've been here 3 years and the first 2 years it never floated. This past year it did, but I had a 6 ft. long rip in the liner that when rain water got above that it seemed to cause it to float. But we have also had tremendous amount of rain in last several months.

    When the liner was out, the contractor recommended a "behind liner drain", basically a 3/4" pipe running from a point near where the deep end vertical wall and slope intersect, to a spot on a down slope in my yard about 2 ft. below the normal water level. I elected not to do this as I had only had problems when the liner was ripped, but now that I seem to be having problems still, I plan on going ahead with it. I know the drainage in the pool area needs to be worked on either with french drain or maybe underground drain off the gutter. The pool is built on a slight slope so grade on one side (about 10 ft. away) is above the water level, and that's where the gutter is. This "behind liner drain" won't stop the ground water, but is supposed to relieve what ever get in there. I can't find any information anywhere about this device and would like to know other's experience or recommendation. If water is coming in from shallow end area, will it migrate all around the pool walls and then through this 3/4" pipe with a grate on it? I guess it's similar to a well point but it's not under the entire pool, and is designed for gravity flow. Any pool builders out there?
    21,000 gallon Inground pool, 18 x 36 'Mountain Lake' with vinyl liner. Hayward 27", 350 lb. Sand filter. 1.5 HP Sta-rite Pump, Pentair booster pump for pressure side cleaner, Polaris 280, CompuPool CPSC-48 SWG, TFT-100

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    In the Industry

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    Nov 2011
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    Moberly,MO
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    Re: Ground Water - Floating Liner - Behind the Liner Drain

    The only thing we do differently that what is being recommended is we put in 4" tile to daylight or a sump pit to remove ground water.
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
    Certified in Hydraulics

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    Join Date
    Feb 2013
    Location
    Metro St. Louis
    Posts
    93

    Re: Ground Water - Floating Liner - Behind the Liner Drain

    Hi Swimcmp. The 4" tile to sump it you mentioned...where does the 4" go exactly? On top of the concrete collar around the perimeter of the pool, before backfill....or somewhere else? Reason I am asking is our St. Louis PB is doing that....but seems a few others talked about 4" tile under the pool floor...or maybe I missunderstood them.
    Paul
    Sterling Steel IGP lagoon 21' x 35' w/6' deep end, Pentair 5g LED lights (x2), Pentair Landscape LED light, Pentiar IntelliFlo VS pump, Pentair 420 Cartridge filter, Pentair IC20, 4 gas Tiki Torches, LoopLoc Ultra Loc II, Deck Jets(x3), Raised Planter Bed with 3 Pentair bronze sheer decents, AquaBot Breeze 4WD, Pentair Legend II

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    In the Industry

    Join Date
    Nov 2011
    Location
    Moberly,MO
    Posts
    978

    Re: Ground Water - Floating Liner - Behind the Liner Drain

    We usually bury the 4" tile below the main drains. This keeps all ground water away.
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
    Certified in Hydraulics

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