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Thread: Combined chlorine remaining high after absorbic acid treatme

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    Join Date
    Jun 2013
    Location
    Indianapolis
    Posts
    2

    Combined chlorine remaining high after absorbic acid treatme

    I have well water that contains copper and iron - 0.1ppm and 0.3ppm, respectively, at last measurement. As a result, I have a light amount of metal staining in my fiberglass pool. At the beginning of the season I wanted to tackle it with an ascorbic acid treatment. I added the polyquat 60 and put in 1/2 lb of ascorbic acid on 5/20/13 and 14 oz of Metal Free. Didn't realize at the time the Metal Free was useless. When I started slowly adding chlorine, I got slightly green, very cloudy water. On 5/24 I added 1 qt of HTH Metal Control - results for the pool at that time were pH 7.2, FC 1.5ppm, CC 2 ppm. I know I was not supposed to shock for at least 2 weeks but the pool looked gross, and I couldn't take it anymore and added 2 gallons of 10% liquid chlorine. The water cleared but now I can't get the CC down to zero. Since 5/28 I have been following the TFP shock process (as opposed to 'breakpoint chlorination') and I cannot get the CC below 2 ppm. I am testing and adding chlorine several times a day. The CC has gone as high as 4ppm, but not lower than 2ppm. The water is beautifully clear. Unfortunately, all staining has returned and then some - I now have staining on my side walls which is a new. Current test results...

    pH 7.4
    FC 0.5 ppm
    CC 2 ppm
    CYA -not showing as readable with test kit - but it was at 35ppm prior to the acid treatment
    TA 125 ppm
    CH 350 ppm

    I am slowly resigning to the fact I may have to just live with the staining. But what do I do about the CC? I only have an 8500 gallon pool - so dumping it is starting to seem like the best option.
    8500 gal, fiberglass, 3/4HP SuperFlo pump, sand filter, Raypak heat pump, Intellichor IC20 SWG (not using yet), Taylor K-2006 FAS-DPD test kit

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Combined chlorine remaining high after absorbic acid tre

    Your CYA might have been turned into ammonia while the FC level was zero during the AA treatment. Ammonia reacts rapidly with chlorine to form CC, which continues to happen until you eventually add enough chlorine to finally burn off all of the ammonia and CC.
    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

  3. Back To Top    #3

    Join Date
    Jun 2013
    Location
    Indianapolis
    Posts
    2

    Re: Combined chlorine remaining high after absorbic acid tre

    Okay - so do I just keep bringing the chlorine up to shock level (10ppm in my case) or should I 'superchlorinate' to over 20ppm? Neither seems to be budging the CC below 2ppm.
    8500 gal, fiberglass, 3/4HP SuperFlo pump, sand filter, Raypak heat pump, Intellichor IC20 SWG (not using yet), Taylor K-2006 FAS-DPD test kit

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