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Thread: Amonia - what causes the CYA to turn into it? prevent it?

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    Join Date
    Jun 2012
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    NJ
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    Amonia - what causes the CYA to turn into it? prevent it?

    We opened the pool - CYA was <20, FC = 0 and as I started bleach it wasn't holding at all. From searching on here it seems like it was ammonia. I just kept testing and adding bleach and the water turned clear and the chlorine started to hold.
    I didn't have time last week when this was all going on to ask about it.
    It seems like it was ammonia which from what I searched said a bacteria converts the CYA to ammonia. Are there things to do to prevent this over the winter? Any rhyme or reason to when it happens?

    I am guessing there is not because then people could just do it to lower the CYA instead of draining...
    Just trying to learn for the future
    Thanks
    NJ
    35,000 gallons, DE filter, IG plaster
    TF-100

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Amonia - what causes the CYA to turn into it? prevent it

    Certain kinds of soil bacteria can convert CYA into ammonia. This can only happen when the FC level is zero. Also, the ammonia will outgas eventually, so you can lose CYA without ending up with ammonia (if enough time has passed).

    This usually only happens over the winter, since you should be maintaining an FC level the rest of the time. Unfortunately there is no telling if it will or will not happen in any given pool.
    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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    Jun 2012
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    NJ
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    Re: Amonia - what causes the CYA to turn into it? prevent it

    ok thanks so nothing we can do over the winter to prevent it then
    thanks to this site it only took one day and a ton of bleach and we were back in business so not the worst thing in the world
    NJ
    35,000 gallons, DE filter, IG plaster
    TF-100

  4. Back To Top    #4

    Join Date
    Mar 2007
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    San Rafael, CA USA
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    Re: Amonia - what causes the CYA to turn into it? prevent it

    If you close your pool late enough so that the water temp is cold and you open early enough in spring while the water is still cold, and if you use an opaque cover, then the chlorine you add when you close may last through the winter and prevent bacteria from growing.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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