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Thread: Evaporation and chemical balancing

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    Evaporation and chemical balancing

    I have a question regarding evaporation and CYA balancing. My pool seems to evaporate a significant amount of water. It is in fact in the sun all day. From when I opened the pool I have noticed a gradual reduction in CYA. I have tried to look for leakage, but unsuccessful. This would explain the CYA loss when I add water. Does the loss of CYA clearly indicate a leak or is it possible that I am loosing some of the dissolved CYA in the evaporation?

    Thanks to the assistance the pool has been very very low maintenance and requires approximately 2 gallons of 10% hyupochlorine a week. This water loss situation is annoying and would be nice to know if I need to be more diligent in my leak investigation (I have spent several hours looking).

    Thanks for you help.

    Just to put levels:
    pH - 7.5
    FC - 5
    CC - 0
    TA - 90
    CYA - 35
    Temp: 82F
    Borate - 50
    17,000 gal. (27' round) with Jacuzzi Laser Sand Filter 250L, Hayward 1.5 HP pump, 70 GPM

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Evaporation and chemical balancing

    You should expect to lose a little CYA over time due to splash out and backwashing (if you backwash). But you shouldn't lose very much. Evaporation does not change the CYA level. Water evaporates, but CYA does not. The CYA stays in the pool.

    Another thing to keep in mind is that the CYA test really isn't very precise. You should expect it to vary by +-10 even when the CYA level remains constant. So you might have a leak, or you might just have "noise" in your test results.
    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

  3. Back To Top    #3

    Re: Evaporation and chemical balancing

    Thank you for the information. That is what I expected (CYA to not evaporate) but wanted to clarify. I didn't realize the test may vary that much, but I can understand why it would.

    Sorry for the long delay on response, was out of town for the long weekend. My dad told me the amount I am filling a week is consistent to what he would have to in his pool. So I really could have no issue

    Thanks again!
    17,000 gal. (27' round) with Jacuzzi Laser Sand Filter 250L, Hayward 1.5 HP pump, 70 GPM

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