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Thread: Liner stain that defies treatment

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    Join Date
    Jun 2014
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    jasper, IN
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    Liner stain that defies treatment

    Over the last couple of years, I've had a large amount of leaves enter my pool over the fall and winter, then sit until spring. Last summer, I noticed the liner had taken on a distinct greenish stain. I first assumed algae, but setting a chlorine tablet against it provided zero results. A vitamin C tablet quickly brightened the liner to a lovely crystal blue. So, I assume I have mineral or metal stains.

    Last year, I reduced the chlorine to zero, dumped ascorbic acid in the pool and within hours the liner was perfect looking. However, the stain came back within a few days of restoring the chlorine and ph levels. I researched and found I needed a sequestrant.

    This year, before the season started, I bought a couple of pounds of ascorbic acid and two quarts of Pro Team metal magic. My plan was to get the water cleaned up (remove leaves, chlorinate hard, and filter continuously), then drop the chlorine to zero, do the ascorbic acid, then the metal magic.

    However, after hitting the pool hard with chlorine for a couple of days, I noticed that the liner had cleared up! When I checked, the pool was very acidic (6.8). Now I figured the acidity has cleared the stain, but that it would come back when I got the ph right, so I got the ph up to 7.2 and added the Metal Magic. I let the filter run continuously for a couple of days, then went back to a normal routine. I never noticed any clouding of the water, as I've read that others have seen after using Metal Magic.

    The pool stayed clear for a couple of weeks, and then *boom*. Literally overnight, the stain came back.

    So now I have no idea what to do. Ascorbic acid cleans the liner up beautifully, seemingly indicating metal or mineral stain, but the Metal Magic did squat to keep the stain away.

    I have always used strips to check my chemistry. After reading this forum, I realize they aren't wonderful. I'll buy a reagent kit and post some numbers here after I get it.

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Re: Liner stain that defies treatment

    Welcome to TFP!

    More sequestrant is the key. Sequestrant breaks down slowly over time, so you need to be adding more regularly. Also, the higher the metal level, the higher a sequestrant level you need to maintain.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    jasper, IN
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    Re: Liner stain that defies treatment

    Quote Originally Posted by JasonLion View Post
    Welcome to TFP!

    More sequestrant is the key. Sequestrant breaks down slowly over time, so you need to be adding more regularly. Also, the higher the metal level, the higher a sequestrant level you need to maintain.
    So I need to repeat the whole cycle? In other words, I need to reduce the chlorine to zero, add ascorbic acid, bring ph up, and add Metal Magic? This could get expensive if I have to do too many cycles.

    Would it be better if I just added ascorbic acid, wait for the stain to disappear, drain 1/3 of the water, add water back, and repeat a few times?

    How much water can you safely drain from an above ground pool?

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: Liner stain that defies treatment

    If you have a source of metal free water, then replacing water can be an effective strategy. However, the metals often come from the fill water.

    An above ground pool can almost always be drained to the point where there is still one foot of water in the shallow end.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Join Date
    Jun 2014
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    jasper, IN
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    11

    Re: Liner stain that defies treatment

    If I go the sequestrant route, do I need to take the pH back up and just add more and more sequestrant, or do I need to raise the pH, add sequestrant, then lower pH for each cycle?

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