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Thread: shocking pool

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    shocking pool

    I'm curious to know if the shocking process with a cya of 70 uses the same amount of chlorine a pool with cya of say 30? I know the ppm will be higher but would there be a difference in the total amount used?

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: shocking pool

    It doesn't make a huge difference.

    Although, it is VERY difficult for folks to wrap around bringing their FC to almost 30ppm and then holding it there when CYA is 70.

    We suggest an ideal shock value of 20-30 CYA so your shock FC now is about 12 and that is much more palatable to many.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    East Texas

    Re: shocking pool

    Makes sense that to get more ppm of FC in the water you'd have to add a larger total amount of it.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
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    elwood58's Avatar
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    May 2012
    Sun City West Arizona (2nd Home)

    Re: shocking pool

    Pool Calculator is your friend.
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    Re: shocking pool

    yes. I understand that you have to bring the ppm to 30, but will the total chlorine usage from start of shock to 2 week after overnight loss test (pass) be the same, regardless of the cya in the pool. I'm trying to get my head around the high shock level. Oh yah I have a swg. I would think it would have to be the same because there is only so much organics in the water.

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    linen's Avatar
    Join Date
    Jul 2010
    Twin Cities, MN

    Re: shocking pool

    You will lose a little more FC from the sun during the day at the required higher FC levels even with the higher cya.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    jcowart's Avatar
    Join Date
    Jun 2012
    Labelle, TX

    Re: shocking pool

    I know I helped a friend last summer with her pool. I can say even with high CYA the loss was higher at shock level even with the CC coming down. Once the process was over it leveled out. I just figured the FC overcame the CYA and a lot was lost to the sun. Once it was back down in the range pool calc called for her loss per day averaged 1.5ppm. Side note is she is no longer pool stored and took control of her pool.
    17500 gallon Doughboy AGP, Hayward DE filter, waiting for the 1.5hp DB pump to go out.
    Learn to take the advice here and be trouble free or use the pool store's advice. "You can't do both and get very far"

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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: shocking pool

    You are correct that the rate of FC loss, even in percentage terms, is higher at higher FC/CYA ratios such as shock level. And yes, this is because a higher percentage of the chlorine is unbound from CYA and therefore breaking down from the UV in sunlight more rapidly.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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