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Thread: Newbie CYA question

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    Join Date
    Jun 2009
    Central NJ

    Newbie CYA question

    Is cyanuric acid (CYA) only reduced through the removal/replacement of pool water, or does it break down or decay naturally over time (e.g. during the months the pool is closed)?

    My lame test strips (a real test kit is still on its way to me) indicate I probably have a CYA level of at least 100. After years of dichlor and trichlor abuse, I'm surprised it's not higher. Who knows, it may well be once I can do a real test. Anyhow I plan to do a partial drain/refill but don't want to take the water level down more than 1 foot at a time (vinyl liner), and probably don't have the time to do more than 2 intentional drain/refills this season. And of course there will be some removal/replacement due to backwashing, vacuuming, etc. But I was curious if CYA breaks down on its own over a lengthy amount of time.
    36K gallon IG pool, vinyl liner
    Hayward sand filter
    Hayward heat pump heater

  2. Back To Top    #2

    Join Date
    May 2007
    Round Rock, TX

    Re: Newbie CYA question

    Typically you have to replace the water to get rid of CYA. There have been reports of CYA breaking down during the off season or when FC goes to 0.

    It has happened to me a few times, but it is not the "norm". You will need to replace some water to lower it.

    If you are seeing 100+ be sure to do a test where you dilute the water to get a better reading as to the true CYA value.

    If you dilute it with non-CYA containing water 50-50, then you can 2x the results and error.

    15,500 gal, inground gunite pool with 7 ft spa, 2 speed pump 2hp/.33hp, 3/4 hp booster pump, Intermatic P1353 timer, AutoPilot SC-48, Sand filter with ZeoBest, Heater, that I never use . . .

  3. Back To Top    #3

    Join Date
    Jan 2009
    Cupertino, CA

    Re: Newbie CYA question

    There have been reports that soil bacteria in a pool with FC 0 will consume CYA and produce ammonia. You then spend big bucks dumping in chlorine to get rid of the ammonia. In most cases it is cheaper to replace the water.
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

  4. Back To Top    #4
    Water_man's Avatar
    Join Date
    Jun 2008
    Brookline, MA

    Re: Newbie CYA question

    In my area three pools, including mine, lost their CYA during the winter closing season. No ammonia was found. All we did was adding CYA and continued with the "program".
    This is my ticket for Heaven (when all's working..) :
    22k Gal gunite IGP, 38 SF Anthony DE filter, 1 HP Hayward Super Pump
    380k BTU Raypak Natural Gas Heater (Model RP405A) and solar cover
    8 gal Liquidator w/ 12% bleach, Dolphin Diagnostic Advantage robotic cleaner. 3800 ppm salt, 50 ppm borates.

  5. Back To Top    #5

    In the Industry

    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: Newbie CYA question

    No one really knows why some pools have unexplained loss of CYA and others don't. Conversion to ammonia is found in some cases but not all. Still a mystery.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    Perfectly Clear Pool Service, Find me on Facebook!

  6. Back To Top    #6
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Newbie CYA question

    CYA drops only very slowly during the pool season, unless you replace a lot of water. It does go down, but not quickly enough to be useful. Over the winter, CYA can go down much more quickly, but that is very unpredictable, sometimes it happens usually it doesn't.
    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

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