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Thread: PH testing when FC is over 10

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    PH testing when FC is over 10

    So how does one go about properly maintaining PH levels if FC is over 10? Is it impossible to do?
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    JasonLion's Avatar
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    Re: PH testing when FC is over 10

    That depends on just how high FC is. With FC between 10 and 15 it is still possible to use the PH test, just assume it is reading a little higher than actual (.1 to .2 high).

    When FC is above 15 there are some things you can do requiring special procedures/equipment, but then if you are following our recommendations you should never get into that situation except when SLAMing, and that only lasts a few days during which PH can generally be ignored.
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    Re: PH testing when FC is over 10

    It also depends if there is CYA in the water, which there usually is. The oxidation of the phenol red by the chlorine is slower when CYA is present so the reading will initially be better but will then drift upwards turning more purple. This is tricky, however, and would be something to see in practice before relying on it as a method.
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    Re: PH testing when FC is over 10

    Sounds like there is no real reliable way to maintain a pool with pucks.
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    Re: PH testing when FC is over 10

    By this I assume you mean that if you were to use Trichlor tabs/pucks then one could raise their FC target as the CYA climbed, but when the FC got high then the pH test would be hard to read. Yes, that is part of the problem but there are other ways to manage the CYA buildup such as doing a partial drain/refill to dilute the water to lower the CYA level (some of this happens from backwashing filters or from summer or winter rain overflow), or use of supplemental products to prevent algae growth if one does not maintain the FC/CYA ratio. There are a lot of pools that use Trichlor and some are lucky enough to have water naturally low in phosphates so don't see algae while others have problems and spend money trying to resolve them. What we propose with a targeted CYA level and using chlorinating liquid or bleach as the primary source of chlorine is the most consistent and stable approach, but it does take a small amount of regular effort to dose the pool regularly.
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