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Thread: Will a digital pH meter read accurately at high chlorine lvs

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    Will a digital pH meter read accurately at high chlorine lvs

    Will a digital pH meter read accurately at high chlorine levels?
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    Mod Squad jblizzle's Avatar
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    Re: Accurate pH test during shock levels with R-007?

    How are you sure they ever read accurately?

    Honestly, I am not sure.
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    Re: Accurate pH test during shock levels with R-007?

    I keep it calibrated so yes I trust it, I'm just not sure about it during the shock treatment.
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    Mod Squad jblizzle's Avatar
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    Re: Accurate pH test during shock levels with R-007?

    You may be able to find some discussion about this, I seem to recall something, but not the end result.
    Jason, TFP Moderator
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    Mike_W's Avatar
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    Re: Will a digital pH meter read accurately at high chlorine

    Why don't you test it? Get a glass of water - measure the pH. Pour in some bleach and see what happens.
    Mike
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    linen's Avatar
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    Re: Will a digital pH meter read accurately at high chlorine

    A digital ph meter is not affected by high FC readings. Of course the meter needs to be calibrated and a reference solution in the range of expected ph should be checked for accuracy.
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    JasonLion's Avatar
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    Re: Will a digital pH meter read accurately at high chlorine

    A properly calibrated electronic PH meter will read correct even at very high FC levels.
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    Patrick_B's Avatar
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    Re: Will a digital pH meter read accurately at high chlorine

    Quote Originally Posted by Mike_W
    Why don't you test it? Get a glass of water - measure the pH. Pour in some bleach and see what happens.
    Mike
    Because this would change the content from PPM to Percent and it would skew the result by changing the water's pH. It might even ruin your sensor if the mixture was strong enough. Trust me, don't do this.

    Jason says it correctly above. Even high PPM FC in a given water sample will not affect any reliable electronic pH meter.

    To the casual reader, any pH meter has to be calibrated regularly to be reliable. Weekly at an absolute minimum, daily is best. This requires expensive reference buffers that will expire. As a rule, only the the most expensive pH meters are reliable enough to rely on for accuracy. These 200-300 or so dollar units won't last long, even in nice clean pool water. If the bulbs ar not maintained and kept wet 24/7--365, they won't last beyond a week or two. You will get lucky with the occasional one, but not too often.
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    Re: Will a digital pH meter read accurately at high chlorine

    Note that the pH does rise when you add a hypochlorite source of chlorine. How much it rises depends on the initial pH, the TA level, whether there is CYA in the water, and whether there are borates. The following gives the pH rise for different scenarios when adding 10 and 20 ppm FC:

    80 ppm TA, 0 ppm CYA
    adding 10 ppm FC
    pH 7.2 to 7.43
    pH 7.5 to 7.76
    pH 7.8 to 8.03
    adding 20 ppm FC
    pH 7.2 to 7.62
    pH 7.5 to 7.93
    pH 7.8 to 8.16

    80 ppm TA, 30 ppm CYA
    adding 10 ppm FC
    pH 7.2 to 7.52
    pH 7.5 to 8.13
    pH 7.8 to 8.48
    adding 20 ppm FC
    pH 7.2 to 8.08
    pH 7.5 to 8.54
    pH 7.8 to 8.74

    80 ppm TA, 30 ppm CYA, 50 ppm Borates
    adding 10 ppm FC
    pH 7.2 to 7.41
    pH 7.5 to 7.73
    pH 7.8 to 7.98
    adding 20 ppm FC
    pH 7.2 to 7.65
    pH 7.5 to 7.91
    pH 7.8 to 8.11

    So you can see that 50 ppm Borates pretty much counteracts the extra pH rise associated with having CYA in the water. CYA causes the pH to move more when you add chlorine because CYA is a hypochlorous acid buffer so when hypochlorite is added, most of it becomes hypochlorous acid that binds to CYA whereas without CYA much more of the hypochlorite remains so.
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