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Thread: Can't hold chlorine levels

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    Can't hold chlorine levels

    I decided to follow this site's recommendation on shocking to clear up some cloudiness that has been hanging around for about 3 weeks. Last test results from the pool store were (waiting on my test kit to arrive):

    FC 0.1 ppm
    CC 0.6 ppm
    pH 7.3
    Total Hardness 290 ppm
    Alkalinity (adj for stablizer) 143 ppm
    CYA 25 ppm

    Those results were halfway through the process early in the morning before adding any more shock for the day. To that point I had used 13 gal of 12.5% pool shock over the period of the previous day to get the FC up to 10 ppm. I was also able to use borax to raise the pH, it had been as low as 6.9. As of right now I have used about 21 gal of 12.5% shock and I have probably used that to get to shock level about 8 times over the last 2 days. The pool is starting to look a little better, but I still can't hold the shock FC. Last night it was about 10 ppm and this morning around 2 ppm (using test strips to get rough levels). Most of the time the pool has been covered with a safety cover during the process so sunlight shouldn't be much of a factor. On top of the liquid shock, I continued using my feeder dissolving about 8-12 oz. of trichlor per day ( I know I shouldn't do that to run the FC overnight test, but I'm nowhere close to holding FC levels yet). Any idea as to what could be absorbing that much chlorine? As I said, the pool is looking clearer and I think the CC level is coming down, but I'm not sure I can get to just losing 1 ppm of FC overnight at this rate.

    Thanks!
    30000 gal inground; vinyl liner; sand filter;

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    tjwaggoner's Avatar
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    May 2012
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    Ashland KY
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    Re: Can't hold chlorine levels

    I think you should really get a good test kit. Strips are not thought to be reliable enough for shocking a pool. You need to be able to acurately measure higher FC levels and the FAS/DPD test is just the best way to do it. Keep using your liquid Cl while its being shipped then check and see where you are.
    10,000gal fiberglass kidney
    3/4 hp whisperflo
    Sand dollar SD80
    IC40 SWCG
    (2) PAL2000 multi colored LED lights
    all 2" plumbing
    no water features/no spa
    TF Testkit

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    tjwaggoner's Avatar
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    May 2012
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    Ashland KY
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    Re: Can't hold chlorine levels

    There are some great people here that will get you fixed up but they cant help you much without knowing your test results from a good test kit.
    10,000gal fiberglass kidney
    3/4 hp whisperflo
    Sand dollar SD80
    IC40 SWCG
    (2) PAL2000 multi colored LED lights
    all 2" plumbing
    no water features/no spa
    TF Testkit

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    tjwaggoner's Avatar
    Join Date
    May 2012
    Location
    Ashland KY
    Posts
    88

    Re: Can't hold chlorine levels

    My bad: Just saw where you are waiting on it to arrive.....my apologies and congrats. Youre on your way.
    10,000gal fiberglass kidney
    3/4 hp whisperflo
    Sand dollar SD80
    IC40 SWCG
    (2) PAL2000 multi colored LED lights
    all 2" plumbing
    no water features/no spa
    TF Testkit

  5. Back To Top    #5

    Re: Can't hold chlorine levels

    OK, test kit in hand, I get the following numbers:

    FC 0.5 ppm
    CC 1.5 ppm
    PH 7.1
    CH 330
    TA 150
    CYA 20

    That is after adding, over the last 6 days, 24 gallons of 12.5% shock and probably around 12 - 8 oz. trichlor tablets. The pool is now clear, but I still can't hold the chlorine level past 4-5 hours. I added the last gallon this morning, closed the pool (opaque safety cover), and then opened this evening to test, about 10 hours later. I backed off on the tablets because the pool store test I had run yesterday said my CYA was 40, but I'm getting a much lower reading, if I'm doing the test right. Something is apparently still in the water with a CC level of 1.5, but I'm surprised that all that chlorine over the last few days hasn't killed it. Do I need to shock to even higher levels? I've been shooting for 10-12 ppm.

    Thanks!
    30000 gal inground; vinyl liner; sand filter;

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    duraleigh's Avatar
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    Sebring, Florida
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    Re: Can't hold chlorine levels

    You don't need to shock at a higher level but you need to be more consistent. Get your FC back up to Shock.

    It has been low all day which essentially means you have not been shocking the pool during that period.

    Trust your own testing....assume your CYA is 20ppm

    You must keep your FC at shock levels constantly if you expect to complete the process.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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