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Thread: CYA or Chlorine First?

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    CYA or Chlorine First?

    Hi All,

    In ground pool, ~20k gal, closed last year (was sick, long story). Opened about a week ago to a green swamp. CYA measuring zero.

    Have twice added about 10lbs of cya (20lbs total) slowly via skimmer, but understand now after some reading that I may have backwashed much of that out from my sand filter.

    CYA still measuring zero. Added large sock full of cya to skimmer basket last night, and this morning it's completely empty.

    Meanwhile, have of course been adding tons of bleach. TC is up around 30 but FC I'm having trouble keeping above 2. Pool is no longer green, even when I vacuum or sweep, just a milky white with only about 12" of visibility.

    So, clearly I need to get that FC up, but I'm wondering about the CYA and if I should even worry about CYA until I get the pool back in shape. Could all the CYA I've been adding just be "feeding" the contaminants? Should I keep trying to get CYA up WHILE I'm shocking the pool? Or is that just aggravating the problem?

    19,000 IG Vinyl, sand filter, liquid chlor, 1HP pump

  2. Back To Top    #2
    Smykowski's Avatar
    Join Date
    Sep 2011
    Gurnee, IL (North Suburban Chi-town)

    Re: CYA or Chlorine First?

    With your CYA at 0 and your TC so high, it sounds like you have an ammonia issue. We've seen a lot this spring, search for "ammonia" and you'll have plenty of other experiences to see. For now, keep adding bleach until you can get somthig resembling an FC reading of 10, then you can add the CYA and start the SLAM properly.

    Can you post a full set of test results?
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

  3. Back To Top    #3

    Re: CYA or Chlorine First?

    Thanks, I'll read up on ammonia as I don't think I've ever had to deal with that before. I miscalculated earlier. My TC this morning was around 15, not 30. With a few hours of sun, as you can see blow, that plummeted despise adding a couple gallons of shock this AM.

    Just took a full set of readings.

    CYA: Unreadable (0)
    PH: 7.4
    TC: 2
    FC: 1
    TA: 120
    Calcium Hardness (which I haven't typically tested for) is 40.
    Appearance: Still white cloudy with about 12" visibility.

    Clearly I need to go add lots of bleach to get my FC up. Any other recommendations? During the day with bright sun, should I still be trying to keep FC near 10 (seems almost impossible) or just overnight?
    Last edited by phlach; 06-08-2014 at 12:25 PM. Reason: Added Calcium Hardness
    19,000 IG Vinyl, sand filter, liquid chlor, 1HP pump

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: CYA or Chlorine First?

    With the right conditions, all the CYA you had last year turned to ammonia this year. It takes a LOT of bleach to eliminate the ammonia. It will react and consume the bleach almost as fast as you can pour it. So much bleach you start to question your sanity and your test kit.

    Once you eliminate all the ammonia, it should hold better. Then worry about raising CYA. But keep taking it to SLAM.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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