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Thread: Does pH affect CYA measurement?

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    Does pH affect CYA measurement?

    I have been searching a lot on here and elsewhere about CYA tests and effects. I know that temperature and light both affect the test results. Are there any other factors (outside of my eyeballs and the dilution) that might affect the results? Since it is a precipitate, I wondered if pH is a factor within expected ranges.
    Lyle
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    Re: Does pH affect CYA measurement?

    Not that I'm aware of.
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    Patrick_B's Avatar
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    Re: Does pH affect CYA measurement?

    No, not within any reasonable pool water pH range. Perhaps with extremes, but then it would essentially be irrelevant.
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    Re: Does pH affect CYA measurement?

    The melamine solution used in the Taylor CYA test contains pH buffers that lower the pH significantly. This is to maximize the amount of precipitate since melamine cyanurate is soluble in distilled water at around 20 ppm. So if the pH were not lowered, you'd get an artificially low CYA reading or if calibrated it would be inconsistent and dependent on pH. The pH buffer should be strong enough to overcome any normal starting pH to avoid this issue.
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    Re: Does pH affect CYA measurement?

    Thanks.

    I did find this in which chem geek says "If Bioguard uses a CYA test that does not have a strong acid buffer in it, then the melamine-CYA complex may not form if the pH is high which it may very well be after the biodegradation of CYA. In fact, at a pH of 7, the melamine-CYA complex is soluble up to 20 ppm. The Taylor test has an acid buffer in its melamine reagent to maximize precipitation in the CYA test giving accurate results (otherwise, they'd never be able to measure down to 20 ppm). So I think you hit the nail on the head in thinking that the Bioguard CYA test tablet is a poor test reagent that is inaccurate under conditions of a pH out of normal range (especially high pH). "

    I assumed that if I couldn't find it in a post easily, it isn't normally an issue. I do use Taylor so I'm not going to worry about it.
    Lyle
    Professional product developer using & maintaining a dozen or so spas from 150 to 550 gallons, many pools from 1200 to 40,000 gallons (above-ground and in-ground), and a half-dozen test tanks.
    If it's not one thing, it's usually several others!

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