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Thread: FC loss

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    jccams's Avatar
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    FC loss

    Does FC drop faster when you are at high (shock) levels than when you are at normal (maintanence) levels?
    24,000 gal vinyl Lazy L, 1 hp pump, DE Filter, Pentair 250K heater, Letro Legend pressure side pool sweep

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    Re: FC loss

    I find it does, but it could be because I've always shocked when I had lots of organics built up.

    On an unrelated note, I used to live in Dexter right on Baker Street. I was there during the Dexter Days Blaze
    Clearwater, Florida

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    JasonLion's Avatar
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    Re: FC loss

    FC loss due to sunlight is a percentage of your starting FC level, so yes higher starting FC levels means more FC lost to sunlight.
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    jccams's Avatar
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    Re: FC loss

    Thanks Jason. I was thinking it was a percentage of total rather than stricly a straight scale.
    24,000 gal vinyl Lazy L, 1 hp pump, DE Filter, Pentair 250K heater, Letro Legend pressure side pool sweep

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    Re: FC loss

    Most sources of chlorine loss have it be a percentage of chlorine that is lost. There are some exceptions where the chlorine reacts very quickly in which case the amount of consumption is more related to how much there is to which chlorine reacts. So our overnight FC loss rule in theory should allow for higher losses if the shock level is very high (not the FC level, but the FC/CYA ratio), but in practice the <= 1 ppm FC drop overnight is reasonable as a simple rule.
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    jccams's Avatar
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    Re: FC loss

    Am I understanding that since I was at a 23 level and dropped to 21 (CYA 70) overnight that I may not actually have a problem? I may be misinterpreting what was said, but before I go dumping a bunch more bleach in the pool I would like to make sure it is needed.
    24,000 gal vinyl Lazy L, 1 hp pump, DE Filter, Pentair 250K heater, Letro Legend pressure side pool sweep

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    Melt In The Sun's Avatar
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    Re: FC loss

    If you measured 23 after the sun was completely off the pool, and 21 before the sun hit the pool at all, then yes you should continue shocking.
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