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Thread: Need advice on how high to raise chlorine to shock

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    Join Date
    Jul 2011
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    Need advice on how high to raise chlorine to shock

    Hey guys. My pool was light green with all kinds of dirt in it after a crappy pool cover fell apart over the winter.
    I was unable to read the CYA level because I ran out of the chemical used to test that.
    So--is it safe to assume that over the winter it would be down to zero ?

    So Prior to doing anything my measurements were:
    CYA : 0 (based on assumption)
    FC : 0
    PH: 7.1



    I added two packs of dicholor (which would bring CYA up to 12)
    I then added enough chlorine to bring it up to 15.
    I also added enough Borax to bring the PH to 7.4
    I vacuumed thoroughly twice and scrubbed down the sides of the pool liner.

    After a day of no sun, the chlorine went down to 12.
    The pool after all of this looks MUCH better but still cloudy. So here's my questions

    Am I correct in assuming CYA would have started off as zero since I opened the pool?
    If I bring the fc up to 16 to continue killing the algae would that be too high ?
    I will get my CYA chemical tomorrow so I can test it more accurately.

    thanks in advance guys.
    21' All Steel AGP with Resin caps, Heyward S244T Sand Filter, Heyward 1HP 2 speed pump

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    Richard320's Avatar
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    Re: Need advice on how high to raise chlorine to shock

    No. Some people have found their pools sparkling, the CYA unchanged, and residual FC still in the water when they opened. You can't assume it went to zero.

    There's no way to know how high to take FC without knowing the CYA value. With zero CYA, SLAM level is 10. You can safely keep it there, but it may not advance the cleaning any.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Need advice on how high to raise chlorine to shock

    Quote Originally Posted by Richard320 View Post
    No. Some people have found their pools sparkling, the CYA unchanged, and residual FC still in the water when they opened. You can't assume it went to zero.

    There's no way to know how high to take FC without knowing the CYA value. With zero CYA, SLAM level is 10. You can safely keep it there, but it may not advance the cleaning any.
    Thanks. I should have measured CYA but after I took the pool cover off I THEN realized I didn't have any more of the chemical needed to measure. I didnt want the pool to sit in sun with algae so I just went to work.
    BTW --can I get an accurate measurement of CYA while the FC is up around 15 ?
    21' All Steel AGP with Resin caps, Heyward S244T Sand Filter, Heyward 1HP 2 speed pump

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    Richard320's Avatar
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    Re: Need advice on how high to raise chlorine to shock

    Quote Originally Posted by gdog2004 View Post
    Thanks. I should have measured CYA but after I took the pool cover off I THEN realized I didn't have any more of the chemical needed to measure. I didnt want the pool to sit in sun with algae so I just went to work.
    BTW --can I get an accurate measurement of CYA while the FC is up around 15 ?
    Yes. Only pH gets skewed by the high FC. TA may go from green>pink to blue>yellow but the results are still good.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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