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Thread: how much cya would be "normal" to lose ....

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    Swampwoman's Avatar
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    how much cya would be "normal" to lose ....

    Split from cya-t51106.html Butterfly


    I have the same problem -- today while super sunny it seems I'm down to about 25. However, I dosed to 45 at the beginning of the season (first year in this house/pool) so I'm unclear whether it's possible to loose 20 ppm to splash out/rain/refill dilution. My reasoning is that since I'd added borates at the same time, both readings should be about the same, and borate test "seems" closer to the original 50 (color strips, gah!)

    So, I realize every pool is different, but on average, how much cya would be "normal" to loose to splash out after 2 months with daily use? Will test again today. Daily Chlorine use is slightly higher than it was previously, eg 2.5 - 3 ppm per day versus 2 ppm previously (my pool always has a bit of shade in various spots so I'm never direct sun all day, in case you're thinking 2 ppm sounds low.)
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    JasonLion's Avatar
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    Re: how much cya would be "normal" to lose ....

    The CYA test is not all that precise, so you might have actually lost a great deal of CYA, or none at all. The borate test is even worse, so that isn't something worth comparing to.

    CYA loss mostly depends on how much water is replaced, which varies dramatically from pool to pool. In particular, how often do you backwash your filter and how much splashing actually happens have a large effect. A typical pool will fall from 50 to 30 over the course of an entire season, but yours could easily change more or less than that. It is also possible to lose CYA quickly if you have a leak.
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    Swampwoman's Avatar
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    Re: how much cya would be "normal" to lose ....

    Thanks, jason. I just tested again in my normal early moring light and morning sun and it read 35 consistently after several pour backs in different locations, so that sounds reasonably accurate considering the high volume of splash out around here and the recent rain.

    I checked the borates again carefully and I'd guess I'm down maybe 5 to 10 ppm. So for future reference, I can expect to need a very slight replenish of both midsummer, depending on conditions - at least I'll know to be checking for that midseason.

    Think we could get duraleigh and chem geek to team up and devise color drop kit tests for cya and borates? I predict those would sell like hotcakes
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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    Re: how much cya would be "normal" to lose ....

    I think temperature affects this test, and it is only accurate in a narrow range. Something to do with the solubility of the precipitate.

    At the start of this week we had a mini heatwave, and the water got warmed up by the sun to 29 degrees C (sorry don't do F) which is 2-3 degrees warmer than usual. The CYA read around 45 when I was expecting it be about 55.

    Now the weather and pool temperature are back to normal (i.e. a British summer with clouds and rain) and I'm getting the reading I expect based on what I added and where the readings have been before.

    I seem to remember when the water was really cold before we put the heater on, the CYA test was under-reading as well.

    I use a photometer, so it's not my eyes or the lighting.
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