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Thread: Does CYA have a shelf life?

  1. Back To Top    #1

    Join Date
    Jan 2010
    Southeast Missouri

    Does CYA have a shelf life?

    Hi All,

    I recently replaced some water through backwashing, too much rain, etc. My CYA went from 50 to 30 so I wanted to get it back around 40. The pool calculator says for 16,100 gal I needed 22 oz by volume of stabilizer to go from 30 to 40. I got the stabilizer (100% cyanatic acid) at Lowes and added 22 oz in a sock in front of the skimmer. Waited a week, and it still tested at 30, no increase at all. I then added 45 oz by same method shooting for 50 this time and waited another week. The last reading was barely over 40. So, it took 67 oz to get from 30 to 40. Could the CYA I bought be old and weak?

    Here are my latest test results.

    FC 5.0
    CC 0.0
    TC 5.0
    pH 7.6
    TA 100
    CH 210
    CYA ~42
    Water temp 75 deg.

    Repeated CYA test 5 times with same results.
    Dave in Sikeston, Mo.
    27' AG, 16K, vinyl, 1.5 HP pump, Pentair Meteor sand filter, Hayward Aqua Rite 25K SWG, Pentair E-Z Vac cleaner, TF100 test kit

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Does CYA have a shelf life?

    CYA doesn't go bad if it is kept in a closed dry container. There are a few places that sell 50% CYA, instead of 100%. Check the label on you package. It is also possible that it is working normally, but the CYA test simply isn't precise enough to tell you what is really happening. The CYA test is +-15 at the best of times.
    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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