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Thread: FC increase much less than expected

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    iam4iam's Avatar
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    FC increase much less than expected

    I just started up my SWG again a few days ago, and was quite surprised to find my increase in FC only about 1/2 of what it was last summer! Is this thread possibly explaining that this could be because my water temperature is currently only 60oF, as opposed to 80oF when I measured the FC increase last summer? And should I also expect a slightly greater increase in pH at the lower water temperature (probably not enough to measure, but just asking)?
    ~18,000 gal (16x32)
    Hayward sand filter
    Circupool RJ45 SWG
    Hayward Max-Flo XL SP2305X7 pump (0.75 HP)

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    Mod Squad jblizzle's Avatar
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    Re: FC increase much less than expected

    Could be that the SWG is not running as much due to the colder water. Could be that your CYA is lower and you are losing more FC to the sun. Could be that there is something growing in you water and consuming the FC
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    iam4iam's Avatar
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    Re: FC increase much less than expected

    Quote Originally Posted by jblizzle View Post
    Could be that the SWG is not running as much due to the colder water.
    As far as I know, it either runs or doesn't run. (In other words, I don't think the 60o causes the SWG to only run part of the time.
    Quote Originally Posted by jblizzle View Post
    Could be that your CYA is lower and you are losing more FC to the sun.
    CYA is lower, but not relevant here, since the SWG was running overnight, not during the day, and I was comparing dusk and dawn readings.
    Quote Originally Posted by jblizzle View Post
    Could be that there is something growing in you water and consuming the FC
    Water is crystal clear and OCL<0.5, so no.
    ~18,000 gal (16x32)
    Hayward sand filter
    Circupool RJ45 SWG
    Hayward Max-Flo XL SP2305X7 pump (0.75 HP)

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    JasonLion's Avatar
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    Re: FC increase much less than expected

    Lower water temperatures will make the SWG less efficient. At lower temperatures the water will be less conductive, so less current passes through, so less chlorine generated. The SWG will increase the voltage to try to compensate, but it has a limited adjustment range and can't fully compensate.
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