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Thread: cya level

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    cya level

    I'm posting this again as it didn't post from last night in the getting started thread, don't know why.

    I have been told by a pool guy that the pool will lose some cya during the summer. Is that because of replacement on evaporated water with city water and rain water?

    Also if this is true, then during the summer it would be OK to use the 3 inch tabs in the floater?

    Any guidance is appreciated, Thanks, John
    16100 gallon rectangle pool built in 1984 including a 5' X 5'x 3' Spa, Diamond Brite in year 2000, Non-SWG Pool

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    elwood58's Avatar
    Join Date
    May 2012
    Sun City West Arizona (2nd Home)

    Re: cya level

    Some CYA, but not much, gets lost due to splash out and back washing. Evaporation leaves CYA behind in the pool.

    Depending on your current CYA level, you might be able to use some Tabs. Go to and put all your test results in. Scroll down to the effects section where you can enter what you plan to add, and see its projected effects on your water chemistry.

    You will find that the members here only recommend using Tabs rarely for vacation chlorination.
    14100 Gal IG MiniPebble, Pentair Intellichlor IC-40 SWG, Sand Filter, Pop Up Cleaning, Intelliflo VS Pump, Aquacal Heatpump/Chiller, 1/4 Acre Desert Landscaped, Lots of Deck. Built in 1984, updated in 2012 and 2014
    "If you don't measure it, you can't manage it!"

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: cya level

    You do lose a little CYA during the summer, but normally just a little. CYA is lost to both water replacement (splash out, backwashing, overflow) and oxidation by chlorine. But again both of these processes are normally quite slow.

    Using trichlor tablets routinely will add far more CYA than you normally lose. Using them now and then is fine as long as you keep track of where your CYA level is and their effect on PH.
    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

  4. Back To Top    #4

    Re: cya level

    Many thanks, I just finished testing my water and got these results
    FC 7.5
    CC .5
    pH 7.8
    TA 80
    CH 250
    CYA 60

    I'll use those tabs for vacation only as I'd like to get the CYA DOWN TO 50 or 40 in the future as I'm in the process of getting my pool diamond brighted in the near future. However looks like my pH is a little high today....any other suggestions appreciated, I'm going to the pool calculated as the next step, Thanks, John
    16100 gallon rectangle pool built in 1984 including a 5' X 5'x 3' Spa, Diamond Brite in year 2000, Non-SWG Pool

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