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Thread: Prognostic Balancing Question

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    svenpup's Avatar
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    Nov 2009
    Sacramento, CA

    Prognostic Balancing Question

    Let's say my pH is 8.0 and my TA is 75 (roughly where I want it).

    The Pool Calculator says to get my pH down to 7.5 would take 23 oz of muriatic acid.

    If I put 23 oz muriatic acid into the "Effects of adding chemicals" section it says that it would lower my TA by 4.

    Does this mean I should also add 20 oz of baking soda to offset the soon to be realized drop in TA?
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    polyvue's Avatar
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    Aug 2009
    Sacramento, California USA

    Re: Prognostic Balancing Question

    In practice, even with the additions of muriatic acid, TA tends to be fairly resilient. Perhaps my observation fits within what you would expect with testing error, but my TA has been between 75 and 95 ppm for months and months and has "resisted" change in spite of countless pints of muriatic acid. More frequent pH adjustments using small amounts of MA are recommended - especially so in winter when the CSI plummets due to low water temperatures. Depending on your other values (CH, Salt, CYA) you probably don't need to lower your pH from 8 to 7.5 ... a higher pH should be OK.

    JasonLion or chem geek can respond regarding how the calculator is intended to work.
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    duraleigh's Avatar
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    Apr 2007
    Sebring, Florida

    Re: Prognostic Balancing Question

    pH at 8 is too high. I suggest you bring it down to 7.5 sooner rather than later.

    You will not be able to test for the 4ppm TA drop since most TA tests are only accurate to plus or minus 10ppm.

    You could certainly add the baking soda if you like but you will likely never be able to tell (test) that it worked. I'd leave it.
    Dave S.
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    JasonLion's Avatar
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    May 2007
    Silver Spring, MD

    Re: Prognostic Balancing Question

    There will always be things raising and lowering the TA. Almost any time the PH changes the TA will also change. So, you shouldn't worry about TA changes of 4 ppm. It is impractical to aim for an exact TA level anyway. It is going to vary somewhat. As long as the TA is +-10 of your desired level, then it is just fine and you don't need to bother adjusting it.

    There is actually an important principal behind this. Don't try to micromanage your levels. You should allow things to vary within reasonable ranges so you aren't constantly adding chemicals. That is why the recommended levels are specified as ranges.
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