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Thread: Auto pool cover enabling some kind of growth?

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    Auto pool cover enabling some kind of growth?

    We've had this problem for a while now and wonder if other folks have seen it, too. Our pool was new last summer and at one point very early on, FC hit zero for a couple of weeks. At first sign of cloudiness we got professional help and also started our education in pool chemistry. The treatment was super chlorination and the pool was back to sparkling soon enough.

    However, all is not perfect. Every time we open the auto cover, there is a thin film on the water's surface. Not over the whole pool, but mostly it is heaviest near the edge where the cover rolls up. It's an oily looking film that sometimes has white flecks in it. If the pool is in direct sunlight, the film will clear in an hour or so. Aside from the film, the water is sparkling.

    One observation is that once the pool is uncovered and open long enough to clear the film, closing and opening the cover results in more film. This leads me to believe that whatever I'm dealing with is on the underside of the auto cover. There also seems to be a correlation with the water temperature - the warmer the water, the more film on cover open.

    I've tried scrubbing the underside of the cover with bleach from within the pool. That was a nasty bit of work that didn't clear things up. It may have lessened the amount of film initially, but it's back to where it was pre-scrub.

    So, anyone have experience with this? I'd love to know what I'm dealing with. I'd love to know how to treat it. And in the meantime, is it safe to swim?



    35k gallon
    FC=3; TC=3; CC=0
    Water temp = between 70* and 80*

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Auto pool cover enabling some kind of growth?

    Welcome to TFP!

    First, it is important for the pool to get a little sunlight even if you aren't using it. A few hours a week should be plenty.

    What you describe sounds like organic oils. Raising the FC level a little should take care of it (though not if there is something more serious going on at the same time). With CYA at 40, FC of 3 is the lowest you should ever allow it to get anyway.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    YippeeSkippy's Avatar
    Join Date
    Jan 2012
    'burbs of Augusta, Georgia

    Re: Auto pool cover enabling some kind of growth?

    I haven't noticed anything like this under my cover. Could it be pollen that gets under the edge and collects? I do notice your chlorine level is kinda low for that CYA level so perhaps you've got some low level algae living there?
    12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub. Our pool build--> Our Pool Solved Our Sloping Yard Skippy's Cheap Pool Cooler -->Skippy's New Fountain
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    In the Industry

    Join Date
    Nov 2011

    Re: Auto pool cover enabling some kind of growth?

    Jay the auto cover is some to blame. I sell alto of auto covers and what we see is a need to run fc higher than normal, maybe as much as fifty percent for a few days out of a month. We have yet to find anyone that can tell us for sure what it is. We have also found that we need homeowners to keep the pool open to sunlight maybe one to two days of the week to get the uv to it. We have tried a product from natural chemistry that is geared toward a white mold and have had some success with that.
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
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    Mod Squad Patrick_B's Avatar
    Join Date
    Jun 2011

    Re: Auto pool cover enabling some kind of growth?

    This sounds like it could be bacteria growing under there to me, especially if it is growing on the cover's underside. It is a bit of a guess but not a wild one, and it wouldn't surprise me at all based on the description.
    TFP Moderator
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    Smykowski's Avatar
    Join Date
    Sep 2011
    Gurnee, IL (North Suburban Chi-town)

    Re: Auto pool cover enabling some kind of growth?

    I'd try running the FC higher for a few days. Maybe make 5 or 6 your personal min and see what happens.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Join Date
    Aug 2011
    Cochranville, PA

    Re: Auto pool cover enabling some kind of growth?

    Any chance you have some sort of oil from the mechanics of the auto cover leaking?
    1) The size of your pool in gallons 4440.
    2) The type filter you have is an Intex 2500 gph and it has a re-useable fabric filter
    3) If your pool is an AG (above ground)
    4) Intex 15 by 48 metal frame.
    5) If you know, tell us the size pump 2500gph and the size (flow rate) of your filter.
    Southeastern, Pennsylvania.

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