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Thread: Lower CYA first or get algae under control first

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    Lower CYA first or get algae under control first


    Great site and great information/support.

    So my in laws (who are also the next door neighbors) put in their/our first pool 18 months ago (Above ground, 11,000 gallons). They have been fighting an algae problem since last fall (not much was down over the winter).

    I have finally convinced them to stop going to the pool store and use the BBB method to battle the algae and maintain the pool. As it stands the pool is a nice Mountain Dew color and the FC level is still dropping overnight (28 to 14 last night--CC 2).

    Unfortunately, because of the all of the pucks and shock they dumped into the pool, the CYA level is now 90-120 (depending on who's numbers you use).

    My question is should I do a water change out (60% per the calculator) to lower the CYA level now or wait until I get the algae under control and then do the water change out?

    My temptation is to change out the water now to save on the truck loads of bleach required, but I am also concerned about introducing a new variable into the equation.

    Any advice would be appreciated.

    The only comment I would make is that I am in Central Texas and the pool is in full sunlight. I had seen some info on the internet that pools under those conditions should have a higher CYA level to protect the FC levels.

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    duraleigh's Avatar
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    Apr 2007
    Sebring, Florida

    Re: Lower CYA first or get algae under control first

    the CYA level is now 90-120 (depending on who's numbers you use)
    . You and your in-laws should have a test kit you can trust if you want to practice what we teach.

    Bring your CYA down to 50 and then shock the pool.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Lower CYA first or get algae under control first

    I am new, so take my advice as such. But it is my thought that at those CYA levels the amount of free chlorine needed for shock is very high and seems like a waste. In fact according to this:
    the shock level you are using is too low to be truly affective at your tested CYA levels.

    I would do a partial drain to bring the CYA numbers down first. I wouldn't worry about any "new variables" because you are going to have to do it eventually anyway. Plus the only thing that might need replacing would be CH since you don't seem to be using salt or borates (but sometimes fill water has high CH levels anyway). I think you will be much happier with the battle against algae with the recommended CYA level of 30-50 rather than what you have. Definitely get a test kit so you know the right numbers. It will be well worth it in the end.
    Screened in 15,000 gallon in-ground plaster SWG pool with attached spa. Borates 40-50ppm. 1.5 HP pump. Propane heater. Taylor K-2006 test kit.

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