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Thread: CYA vanished over winter?

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    Join Date
    Aug 2011
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    Winnipeg, Manitoba, Canada
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    CYA vanished over winter?

    I have a TF-100 and have been testing CYA pretty regularly during the swimming season here. Last August/September I was getting CYA readings around 30. This spring when I tested, I was getting a reading of 0...it was as clear as if I was testing tap water. The test is working - I tested a friend's pool and it was reading about where I'd expect it compared to last year. There can't have been more than a 1/4 exchange of water between last fall and this spring (and that's an extremely generous estimate). I've been adding CYA slowly to bring it back up but I'm just wondering what happened to my CYA over winter? Anyone seen this before? I thought CYA was forever...
    19,500 gal., IG vinyl, Max-E-Pro 1/2hp pump, 300 sqft cartridge filter (50-100 gpm), Trident Series 2 UV system (52 gpm)

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    Re: CYA vanished over winter?

    There's a soil bacteria which converts CYA into ammonia, it appears this is what happened in your case. If so, you likely need to SLAM.
    Perform a full test of your water with the TF-100.

    If you have CYA->ammonia then you will see a huge increase in CC when you add bleach.

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    Mod Squad Bama Rambler's Avatar
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    Re: CYA vanished over winter?

    As Abi says, it's rare but it happens from time to time.

    I would raise the CYA to 30ppm and at least run an OCLT to see if you need to SLAM.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    ship of fools's Avatar
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    Re: CYA vanished over winter?

    I lose my CYA every winter for whatever reason. I normally wait until i hit 50 or so to close and then open it back up around the same temp and get things rolling.

    This is my 3rd or 4th season using the TFP method and EVERY year i have no CYA to start but the water is always clear and i have never had ammonia issues.

    Sooo .... i just add enough to get to 40 ppm and don't give it another thought!
    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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    Re: CYA vanished over winter?

    Thanks everyone for all the answers. I guess we'll chalk it up to the mystery bacteria. There was no ammonia smell from the pool when I opened it. It cleaned up from greenish murk to crystal clear in 48 hours - I noticed a high CC reading after my first application of 20L of 10.8% chlorine, but the second application produced clear water and no CC. All the numbers have been looking good since.
    19,500 gal., IG vinyl, Max-E-Pro 1/2hp pump, 300 sqft cartridge filter (50-100 gpm), Trident Series 2 UV system (52 gpm)

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    ship of fools's Avatar
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    Re: CYA vanished over winter?

    Quote Originally Posted by Gm0ney View Post
    Thanks everyone for all the answers. I guess we'll chalk it up to the mystery bacteria. There was no ammonia smell from the pool when I opened it. It cleaned up from greenish murk to crystal clear in 48 hours - I noticed a high CC reading after my first application of 20L of 10.8% chlorine, but the second application produced clear water and no CC. All the numbers have been looking good since.
    If you read the posts on here about people dealing with ammonia they are seeing CC readings in excess of 10 for days. From what i understand the process that eliminates the CYA sometimes results in the production of ammonia but not all of the time. We had a cold harsh winter and i closed after the water was cold. I know many people close much earlier and maybe that impacts it in some way.
    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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