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Thread: Cloudy Water / Unusually High FC readings

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    Cloudy Water / Unusually High FC readings

    Hey all, looking for some assistance if possible. I have an in ground 18x36 vinyl lined pool with approx 22,000 gallons of water. The pool also has an auto cover for what it's worth, and it remains closed most of the time.

    Approx. 2 weeks ago I switched from pucks to straight bleach for my sanitizer, as I was concerned that my CYA was creeping up. It's been a bit of a learning curve figuring how much bleach to add to keep the FC up, and it appears that I missed something earlier this week. I'm looking for any advise that people may be able to offer. Here's the history:

    8/16 - FC = 1, TC = 1. I added 1 gallon of 5.25% bleach after the readinng

    8/17 - FC - 4, TC = 4. This was a surprise as the bleach that I added the day before should have added approx 2ppm. I didn't add anything afterwards

    8/18 afternoon
    - Pool starts to get cloudy. I check FC / TC at noon, and I see the following readings: FC = 1, TC = 1.5. I figure that I have some chlorine in the pool, so go out to dinner planning to deal with it when I get back.

    8/18 night - I check readings again that night, and this time read FC = 0, TC = 0.5. Water is even cloudier, and I add 4.25 gallons of 6% bleach. From what I have seen, I had expected this to result in approx 10ppm chlorine addition

    8/19 morning - check readings in the morning, see FC = 20, TC = 20. Again, unusually high readings given how much bleach I added

    8/19 night - check readings again, this time doing a full battery of tests:

    FC = 20
    TC = 20
    pH = 7.3
    CYA = 65
    TA = 140
    Calcium Hardness = 290

    If my chlorine readings are accurate, I would think I have a high enough level to kill whatever is causing the cloudy water, but I'm concerned that something is impacting my readings causing this to be unusually high.

    Any suggestions as to what might be causing that, and what I should do about it? I've yet to add more bleach, and have my filter running on high 24x7.

    18x36 in ground vinyl, approx 22,000 gallons

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    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: Cloudy Water / Unusually High FC readings

    Welcome to TFP!

    What you report is strange.... so I have some q's for you to try and clarify things. What are you testing with? (drop test kit, strips?)

    Are you certain of the bleach % strengths and sizes? 5.25 and 6% bleach usually don't come in gallon size jugs, they usually are sold in the small 96 ounce jugs or they go up to the double-sized biggie jugs, 174-182 oz. The only gallon sized jugs I've seen are the 10-12.5% strength. (It seems like everything sold in the grocery stores are shrinking these days, from Ice Cream that used to be 2 qts and are now 1.5-1.75 qts, to canned food that used to say 16 oz now say 14.75 or 15 oz, yet the prices are the same....sorry rambling here ) So lets confirm exactly how much you used.

    Are you sure your pool is 22,000 gallons?

    In any event, see my signature - the CYA chart... for your CYA your shock level is 24. The pool calculator puts you on the mark at about 20. So you are high enough to kill whatevers growing, but you have to keep adding more bleach until the FC holds overnight to ensure that it is dead. It's good that you are running the filter 24/7. I would keep adding enough bleach to hold you at least at 20 overnight till it holds, and you don't lose any FC overnight in the darkness. Once it holds overnight, you'll know all is well and the FC can drop to normal levels.

    For your CYA of 65, you should maintain your FC between 5-7 ppm at all times, never below 4 or algae will likely take hold. So each night add enough bleach to keep you at 7, so as it drifts down during the day it won't go below 4-5.

    Hope this helps.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner

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