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Thread: Order of chemical additions

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    stev32k's Avatar
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    Mar 2009
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    Mobile, Alabama
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    Order of chemical additions

    The liner in my pool was replaced this week and the water is almost high enough to run the pumps. I've calculated the weight of all the chemicals required but have a question on the order in which they should be added. The chemicals needed are sodium bicarbonate, Calcium chloride, CYA, and chlorine. I tested the water and the results are:

    pH 7.0
    FC .5
    Ca 40
    TA 20
    CYA 0

    I'm assuming the chemicals should be added one and a time and allow enough time between additions to get them mixed in the pool water. So does it make any difference as to which is added first or last?

    Another question - the instructions that came with the vinyl liner said to maintain a minimum Ca concentration of 100 ppm and a maximum free chlorine concentration of 3.0 PPM. I am assuming that the requirement for a minimum Ca level is because there is calcium in the liner or the die used to color the liner. The maximum free chlorine level could be a problem if I need to shock. So my question is - are these concentrations realistic?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Order of chemical additions

    Start by raising the TA.

    Add 2 ppm of chlorine each evening starting the first day you have pump is running and switch to targeting an FC level based on your CYA level beginning 24 hours after you start adding CYA.

    The requirement for CH is not based on anything meaningful. You may want to do it just to maintain your warranty, but there is no other reason to add calcium.

    A max FC of 3 is not realistic unless there is no CYA at all in the water. Having that requirement dates back to before people used/understood CYA.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    stev32k's Avatar
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    Mar 2009
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    Mobile, Alabama
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    Re: Order of chemical additions

    OK, thanks for the quick reply.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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