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Thread: Do high chlorine levels always make false pH readings?

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    Do high chlorine levels always make false pH readings?

    All that I've been reading in the Pool School suggests that high chlorine levels can create false high pH levels. My FC is 20 (CC - 0), and my pH is reading 7.6, which doesn't seem "high" to me. Does pH always read high when chlorine levels are where mine are? If so, should I assume I actually have pH that could be too low, and therefore reducing the efficacy of my sanitizer? (My pH was 7.2 before I shocked).

    Thanks in advance. Everyone here has been so helpful!
    18,000 gallons IG plaster pool
    cartridge filter
    2 speed pump

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    Re: Do high chlorine levels always make false pH readings?

    I have found that pH seems to be pretty accurate as long as the FC/CYA ratio is not too high and the test is read right away. If your pH was 7.2 before shocking and you used sodium hypochlorite, then your pH would not go lower, and would not be too low.

    However, pH can be affected by high chlorine levels and it is good to be careful about trusting the results. Wait for the chlorine to get below 10 ppm and retest.

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    Richard320's Avatar
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    Re: Do high chlorine levels always make false pH readings?

    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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