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Thread: Absorption rate of CYA

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    Absorption rate of CYA

    I wonder if someone can clarify the statement made in "ABCs of Pool Water Chemistry" under The Pool School that "Solid stabilizer can take up to a week to fully register on the test, so don't retest your CYA level for a week after adding some." Does that mean that the stabilizer is not available (or slowly becomes available) during the first week, or only that the standard test does not detect it? In particular, does that mean that any liquid chlorine added during the first week after a refill will get decimated by the sun?

    As a related question, what about the stabilizer that is released by chlorine tablets (trichlor) and chlorine granules (dichlor)? Are these forms of CYA available and/or register on the test sooner?
    Todd Wilson, Fresno, CA (July: 82o avg, 110o max; Dec: 45o avg, 15o min)
    Pool: IG, pebbled, 21K gal, 520 ft2 4-cartridge filter, 1.5 hp pump, Paramount PV3 in-floor cleaning system
    Spa: Stand-alone, 355 gal, 100o - 102o, no ozonator

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    Re: Absorption rate of CYA

    CYA dissolves VERY slowly. So over that week's time, your CYA will slowly creep up. You don't want to test too soon and add more, because if you overshoot, the only way to lower it is to drain some water and refill.

    By 'solid stabilizer' it means not liquid.

    Until you get enough CYA, yes, your chlorine will be depleted faster from the sun.

    I believe dichlor may dissolve faster than the pure CYA, and is what some people use to raise the CYA and add chlorine. Trichlor is slow to dissolve which is why so many people use it as a chlorine source. You can also use this to raise your CYA and add chlorine. The important thing is to test your CYA, and discontinue the use of these products when your CYA is at the right level.

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

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

    Re: Absorption rate of CYA

    CYA from dichlor and trichlor dissolves very rapidly compared to plain stabilizer and registers on the test very quickly. Dichlor dissolves almost instantly, trichlor depends on the form it is in but can be minutes if in a powder. Stabilizer, on the other hand, tends to go into the filter and dissolve very slowly over several days. The amount of time actually required varies from just over a day to almost a week. We say a week to try and cover all the possible cases.

    In practice, a significant percentage of the CYA will dissolve within the first 24 hours. A good basic plan is to assume there isn't any CYA for 24 hours, and then assume that it got to the target level after that. That isn't perfect, but it is close enough.
    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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