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Thread: CYA Loss

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    CYA Loss

    Greetings. At the start of the pool season my CYA was at a perfect 40. Lately (past month) I've noticed an increase in chlorine demand from my pool. On a hunch I did another CYA test and it literally fell to 10. We have had A LOT of sun this year and hardly any rain. I have had to add water to my pool to keep it at the appropriate level because the sun was just evaporating it like crazy. I know you cannot lose CYA through evap but can you lose it by continuously adding fresh (well) water to the pool?? I really am at a loss on this one. I have some CYA on its way to stop the chlorine bleed. Your thoughts on this are greatly appreciated.

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    Mod Squad JVTrain's Avatar
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    Re: CYA Loss

    CYA does decay very slowly in the presence of hypochlorite, slightly faster at elevated FC levels and higher temperatures.

    Check out this thread for more details, specifically some of Richard's responses to questions. It's an in-depth post that might be over some folks' heads, which is fine, but there is some good discussion as well. Degradation of Cyanuric Acid (CYA))

    The short of it is, some CYA loss over time is normal. If you have ruled out any leaks, decay could be a possibility but 30 ppm seems excessive for one season. I routinely see mine drop from 40 to 30 over a couple months during the swim season and end up adding a bit of CYA in July most years or make up for it by floating a few pucks if I'm going to be gone for several days here and there. I also believe that I have a VERY small leak, but have not sleuthed it out yet.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Mod Squad pooldv's Avatar
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    Re: CYA Loss

    Ditto, I had to add some last weekend to get it back to 80. It was between 60 and 70.
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    borjis's Avatar
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    Re: CYA Loss

    There's another thread on this recently.

    CYA dropped to below 30

    Seems some of us have lost quite a bit so far this season, I too have lost 30 ppm in 2 months without any back washing / draining /replacement of any sort.

    This is much higher than what considered normal.

    I have a theory that my neighbors red pine that drops lots of pollen nodules is somehow creating an environment to consume the cya, but that's
    just a theory at this point. (First season with this pool)
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
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    Re: CYA Loss

    Have you guys had a significant amount of evaporation in your pool? I have so far this year because of all the sun we have been getting. This is been one of the warmest and sunniest summers in several years. My pool gets roughly 10 hours of direct sunlight every day.


    22K Gallon, 30 foot round AG
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    borjis's Avatar
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    Re: CYA Loss

    I have to top off 1/4" weekly, but cya doesn't go down from evaporation.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    Re: CYA Loss

    But does continuously having to fill the pool dilute the CYA?


    22K Gallon, 30 foot round AG
    Dual speed 1.5 HP pump
    Cartridge Filter
    Jandy LRZ heater

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    borjis's Avatar
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    Re: CYA Loss

    No, the cya stays in the water.

    The only way to remove it is to drain/replace water. Evaporation only removes water itself.

    When I lost 30 ppm over 2 months, it wasn't even hot outside yet and most of that time was cloudy days.
    I didn't add any water at that time.


    I'm keeping a log of what happens the next 2 months.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    Mod Squad mknauss's Avatar
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    Re: CYA Loss

    I lose 1/2" per day here in the Nevada desert!!!
    Quote Originally Posted by borjis View Post
    I have to top off 1/4" weekly, but cya doesn't go down from evaporation.
    6000 Gallon IG Fiberglass with integrated Spa
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    Marty

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    borjis's Avatar
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    Re: CYA Loss

    I bet!

    I don't think I would live in Nevada without a pool.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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