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Thread: How long before measuring CYA after drain & fill

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    Join Date
    Jun 2014
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    Tucson, AZ
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    860

    How long before measuring CYA after drain & fill

    For CYA test, what is the recommended amount of mixing time after a partial drain and fill. In my case, I drained approximately 900 gallons on a 17000 gal pool (~ 5%) and refilled with city water.

    I tested the following day but the total run time of the pumps during that period before testing probably was less than 8 hours. I went from a previous reading of 60ppm to now reading 40ppm.

    So either my previous reading was too high or my current reading too low. There's been a little rain water here and there but nothing that significantly altered the pool volume. Water is crystal clear and sparkly.



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    duraleigh's Avatar
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    Apr 2007
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    Sebring, Florida
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    Re: How long before measuring CYA after drain & fill

    Since the CYA was already "mixed" in your pool, there is no mixing time...the results should be essentially instantaneous.

    If you drain 900 gallons from a 17k pool, you should experience a 5% reduction in CYA....so down to 57% instead of 60....not much.

    I can't tell you which test was wrong so you might just split the difference and call your CYA 50 ppm.....that should work.

    The pump run time is, essentially, not relevant. 30-60 minutes should be plenty to get everything blended.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Jun 2014
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    Tucson, AZ
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    860

    Re: How long before measuring CYA after drain & fill

    Yeah, I'm going to retest again tomorrow. I should probably buy the 50ppm CYA standard from TFTestKits to calibrate my eyeball to what the black dot disappearance should look like. I definitely tried hard to make sure I used similar lighting conditions. Perhaps I have Superman-like X-ray vision

    I have a bucket of 1" spa trichlor tablets so if I felt like the CYA was truly low, I can always try to bump it a bit with those since they're smaller than a big 'ol 3" puck.

    Thanks. I'm not going to lose too much sleep over this...just needed to do a sanity check...

    Insane neurotic pool owner, CHECK!



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