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Thread: High CYA = Green water

  1. Back To Top    #1

    Join Date
    Jun 2011
    San Antonio, TX

    High CYA = Green water

    First of all, MAJOR THANK YOUs to the Admins and contributors of this site. I've owned a pool for about 7 years now, and I'm finally making a dedication to learning the chemistry. This site has great down to earth articles that are easy to understand.


    55,000 gallon pool turned green on me.

    While I waited for my TF-100 kit to arrive (bought through TFP), I tested with test strips and noticed my CYA was through the roof. Probably because my dumb***** kept adding tabs to the pool (inadvertently adding stablizer with every dose and sending my CYA through the roof)

    After my TF100 kit came in, I confirmed the test strips were pretty accurate:

    My numbers are as follows:
    FC 10
    Alk 80
    ph 7.2
    CYA 150

    Because I couldn't lower the CYA any other way, I went ahead and drained about 80% of the pool. Totally random, we got about 9.5 inches of rain the day I began draining the pool.

    So the pool is only 20% full at the moment, and water is green as a slime monster. I haven't tested the water since the drain. I will be moving to the BBB method as I start to refill the pool.

    My question is... should I try to kill the algae while the pool is only 20% full, or should I go ahead and start the refill and then move to kill the algae?

    DrummerDan in San Antonio, TX
    55k gal, IG plaster, Single speed pump, Giant sand filter, Manual chlorination through Skimmer basket and tab floater, Kleen Machine robotic pool cleaner ran about twice a week
    DrummerDan in San Antonio, TX, 55k gal, Rectangular in ground plaster, Single speed pump, Giant sand filter, Polaris robotic pool cleaner, CompuPool Salt-Gen

  2. Back To Top    #2
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: High CYA = Green water

    I'd be pretty impatient myself, so I'd probably throw about 3 gallons of chlorine in and let the hose flow disperse it. If the pool is 20% full, the water in there is10,000 gallons at 150 CYA, so shock level is up around 33 FC. 3 gallons of 8.25% Chlorox in 10,000 gallons will take you up to about 28, so you should start seeing some clearing. You can't really do the shock process without circulation, but it ought to give a little head start.
    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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