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Thread: white mold/chlorine demand

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    Join Date
    May 2013
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    white mold/chlorine demand

    Hello! I had white mold about 2 and a half weeks ago. I have since shocked, brushed, took steps out, lights, skimmers, changed sand, emptied and cleaned filter, cleaned, cleaned, and then cleaned more! It was everywhere.

    Right now, I my water is clear and beautiful, but I am having a problem holding chlorine. At the beginning of this process, my cya was 70, after keeping my chlorine running at full, it is now 137 (which I know is really high and we are working on draining some everynight to lower it). I am no longer using the tablets. Just liquid chlorine. Last night, I brought my shock level up to 56 by using the cya chart. This morning it was 45, so I added 2 gallons (per the calculator) and now 1.5 hour later, it is 41. I have been able to keep some chlorine overnight, but it seems that during the day, it just will not hold. Two nights ago, I had the chlorine at 10 and in the morning it was 8.5.

    Do I just continue to try to keep the level at 56 during the day until it stays, per the shock process? I am at my wits end!! lol

    My levels yesterday. I do have a taylor k-2006 test kit.
    cya - 137 per pool store (my test said over 100)
    TC - 41 - right now
    CC - 0
    pH - 7.8 - yesterday
    TA - 120
    Adj. TA - 81 (pool store) Not sure the difference between these two TAs.

    I haven't tested with my kit today (except chlorine) , not sure levels would be accurate with high shock.

    Thanks for any help!
    Jackie
    IG vinyl 26,000 gal., Hayward S-200 sand filter, Hayward HP600 heat pump

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    JasonLion's Avatar
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    Re: white mold/chlorine demand

    Welcome to TFP!

    Just ignore Adjusted TA. We always just use TA numbers directly from the test kit around here. ATA used to be used when calculating the saturation index, but there are simpler approaches to figuring out SI (if you even need to know it which most people don't) which make calculating ATA pointless.

    High CYA levels slow down the shock process a little. It appears that the chlorine is still actively breaking down the remnants of the white water mould, as indicated by the rapid chlorine loss. Until that process is complete, ie the FC level stops dropping so quickly and does not drop overnight, you should maintain shock level.
    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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    Re: white mold/chlorine demand

    Thanks!
    IG vinyl 26,000 gal., Hayward S-200 sand filter, Hayward HP600 heat pump

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    Re: white mold/chlorine demand

    Okay, another question! Right now my CYA is 120, so we have brought it down a little! The shock level on the pool calculator says shock at CYA level of 120 is 28. On the CYA/Chlorine chart it says that shock level is 46.7. Am I looking or putting something in incorrect? What should my shock level be for CYA of 120? Thanks!

    Jackie
    IG vinyl 26,000 gal., Hayward S-200 sand filter, Hayward HP600 heat pump

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    Re: white mold/chlorine demand

    Okay, it held a shock value of 46 all night, no ccs and water is clear. So I am going to let it go down today. With a CYA of 120 what is a safe chlorine range to swim?

    I still am not understanding, the difference in the CYA/Chlorine chart and the pool calculator for shock levels. If don't know if I am doing something wrong. I just want to be consistent...And make sure I get rid of this stuff!! Lol. What would the shock level be for a CYA of 120?

    I appreciate the help. Thanks!
    IG vinyl 26,000 gal., Hayward S-200 sand filter, Hayward HP600 heat pump

  6. Back To Top    #6
    JasonLion's Avatar
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    Re: white mold/chlorine demand

    Keep in mind that none of the CYA tests are at all precise when measuring values over 100. Your CYA level could be anywhere from 70 to several hundred. You really really want to replace water to get CYA down to something reasonable.

    Assuming CYA really is 120, target FC levels for normal operation are between 9 and 15, and never below 9.
    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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    Re: white mold/chlorine demand

    OK. Thanks! We are working on draining and refilling. We have a well, so it is going to take some time. I did the CYA test with half water/half pool water, hoping that would be more reliable.

    Thanks!
    IG vinyl 26,000 gal., Hayward S-200 sand filter, Hayward HP600 heat pump

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