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Thread: pH level and shocking pool

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    pH level and shocking pool

    Me again. Still fighting this incredibly persistent black algae. Went back to shocking the pool when FC dropped after several nights of it staying OK. Had 2 nights with no FC loss so started dropping the FC again. Still brushing daily with SS brush.

    Last night I had a 5 ppm loss of FC! ARGH We have had a big drop in temperature and a lot of wind the past 24 hours. We get a lot of debris in our pool but we cleaned all the big debris out last night before going to bed and left the pump and sweep running. I'm assuming it's the black algae causing the overnight FC loss to be on the safe side but was wondering if the extra debris in the pool could have caused this drop. Either way I figured I'd better shock again to make sure we don't get any new problems.

    Anyway, I am back to shocking the pool. Here's my question:

    Will I get better results if I adjust my pH level down some? Does it matter what order I adjust the chemicals?

    Here are my current test results:

    FC: 12 (going to bring this back up to 20 this morning)
    CC: 0.5
    pH: 7.8 (tested at FC of 12)
    TA 110
    CH 175
    CYA 55



    15,000 IG white plaster
    Hayward cartridge filter new pumps/filter system this year
    17,000 gal IGP, White plaster, Hayward Swimclear Cartridge Filter system, Sta-Rite Max-e-pro 1/2 hp pump; 3/4 hp booster pump

    Sacramento, CA

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    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: pH level and shocking pool

    Hi, Patricia,

    I have not followed your posts closely but have these comments:

    1. Lowering your pH down to 7.2 is somewhat helpful but don't consider it as the reason your not defeating the algae. a pH of 7.8 is in the "comfort zone" but 7.2 will make the FC somewhat more effective.......just somewhat.

    2. The key to black algae is persistence and constantly high FC levels. With your CYA of 55 I would say that an FC of 8ppm+ is adequate but you must be very constant......that means keeping the FC between 8ppm and 12ppm or so for possibly weeks until the black algae disappears....never letting it dip below the minimum.

    I don't think it's necessary to shock your pool but it doesn't hurt, either. Brushing the algae twice daily is very helpful just make sure you have that FC in the pool when you expose the surface of the algae with the brush so you can keep killing it.

    It may take weeks to remove all of it and you may well have to keep your pool at a higher FC than normal forever but you've got to get rid of the visible stuff first with your determined, constant applications of brushing and chlorine.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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