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Thread: Would pH change over time?

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    Would pH change over time?

    I'm trying to make sure I have decent readings and I got a sample in a plastic bottle with a known pH value. Like an idiot, I didn't test it when I first got it and when I did (almost three weeks later), I got a slightly lower value than I was supposed to. Would sitting in the plastic bottle too long do that?

    Also, does anyone have any suggestions on where to buy waters with known concentrations (ph, cya, alkalinty, whatever) for this purpose?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    JasonLion's Avatar
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    Re: Would pH change over time?

    If you have a sample specifically designed to be a calibration solution then it should still be good several weeks later. If you got a sample somewhere else, tap water, pool water, etc, then the PH is likely to have changed. Calibration solutions are specifically designed to have stable readings even after a fairly long time in storage, but other sources of water will not have that properly.

    Taylor makes various calibration solutions. TFTestKits.net carries several of them, as do various places on the Internet.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Would pH change over time?

    Thanks Jason for the speedy reply! I got a pH of 7.4 and the bottle was supposed to be 7.57 with a range of 7.5-7.7. Alkalinity read 88 (and 84, second reading) and was supposed to be 80 (range of 75-85). CH was waaay off, but I know the reagents are old and frankly, with my vinyl liner, my learnings here tell me not to worry too much about CH anyway.

    This is of course with my "ColorQ", but the big question is: Am I being overly anal about this and these numbers are close enough that I should quit worrying about it?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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    JasonLion's Avatar
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    Re: Would pH change over time?

    I wouldn't worry about it at all. The tests are all only approximate to begin with and you can be +-20% and still do alright.

    Only the PH is far enough off to be outside the expected precision of the test. The TA test is +-25, CH +-30 (or +-50 depending how high it is), and so on. PH is +-0.1, so that is the only one that could be considered "wrong", and PH is by far the most likely number to have changed during storage.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Would pH change over time?

    Thanks. I've been rapidly coming to the conclusion that I'm overthinking all this. I guess I needed a sanity check and level set.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

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