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Thread: Add CYA or shock first?

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    oletrout's Avatar
    Join Date
    May 2009
    Hamilton, Ontario

    Add CYA or shock first?

    Got my pool all set up and clear-THANK YOU for the help. Now I told my very busy neighbor I would try and help him with his 190,000 Liter rectangular 20x50x6 with vinyl liner and SWG. Just took some tests and got the following:

    FC=1--chart says SHOCK to 24= add 70 Liters--Is shocking to 24 the correct marker?


    PH=8+---chart says add 2.7L Muriatic Acid

    CYA=0---chart says add 13 Kilo

    My question is in what order should these #'s be adjusted?
    Southern Ontario. Concrete Lazy L shape pool painted in 2005 with 2 part epoxy paint ,42 x 20 , 2.5 ft deep in shallow end , 8 ft in deep end, with what i calculate as an average depth of 6 to 6.5 ft. or approx 38300 Gal. 1HP pump , Hayward sand filter model S-220T rated at 2.64 ft.2 , 52 GPM , Intellichlor IC40 CG

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Add CYA or shock first?

    You must follow the shock process as prescribed in the article in pool school.

    1. Lower your pH into the 7's first.

    2. Add enough CYA to get to 30 ppm

    3. Follow the shock process article precisely.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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