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Thread: PH testing above 10 FC

  1. Back To Top    #1

    Join Date
    Mar 2011
    Houston, TX

    PH testing above 10 FC

    Read several posts that say PH testing is inaccurate above 10 FC. With a CYA of 100 + I have a target of 12 FC. I typically test after 6 pm when my FC has dropped to around 8 so is my PH test accurate or not?
    18,500 gallons, Cartridge Filter, In Ground Plaster. Jandy CL460 Filter

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: PH testing above 10 FC

    When FC is between 10 and 15, the PH test is usable, but it will read a little higher than actual. There is no way of knowing exactly how much off it will be in your particular situation, typically somewhere between right on to 0.2 higher than actual. The error gets larger the higher the FC level is, and then somewhere between 18 and 22 it starts being wildly wrong and you can't use it at all.
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