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Thread: CYA - Myth or could it be?

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    CYA - Myth or could it be?

    New to this board but not to pool ownership. Was pool stored in the beginning but have since seen the light.

    I used to use trichlor and back in the day, ran into the infamous high CYA issues so often discussed here. I've always been told that the only way to "economically" reduce CYA levels is to drain and replace a portion of the water.

    Well, the other day I was in a pool store and overheard an employee discussing high CYA with a customer.
    Customer says: "guess I need to drain and replace"

    Employee says: "not until daytime highs drop below 80 degrees or you risk plaster damage"

    BUT THEN employee adds: "you could try siphoning or pumping off the top since most of the CYA is in the top few inches of the water when the pump isn't circulating"

    I've heard this sort of thing from other pool stores and pool maintenance guys over the years and I wonder, could it actually be true or just another urban pool legend?

    I tried measuring CYA in samples in my pool from different depths and could not discern any meaningful differences so I think the answer is myth, but to the chemistry gurus, is there any scientific justification to what theses "pool pros" assert?

    Sunny Fl.
    ingound gunite pool
    with a cartage filter

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    Re: CYA - Myth or could it be?

    Quote Originally Posted by BYAO
    I've always been told that the only way to "economically" reduce CYA levels is to drain and replace a portion of the water.
    Just an FYI, a alternative to drain and refill is Mobile Reverse Osmosis (Puripool Process) if it is available in your area.

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    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: CYA - Myth or could it be?

    just another urban pool legend?
    Yep!! It mixes in your pool just like chlorine, acid, etc. Usually those urban legends have some degree of logic behind them but I don't think one does.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    chessie6's Avatar
    Join Date
    May 2010
    East Hartford, Connecticut

    Re: CYA - Myth or could it be?

    Oh fooey - for a couple minutes I had my hopes up
    Summer: 19 x 37 Pacific Graphex IG modified oval, aztec marine vinyl liner, 24,000 gal, 3.5 feet to 8 feet, 1 hp Hayward C4025 Swim Clear 4-cartridge filter, chlorine pucks or bleach depending on CYA levels, 1 super wide mouth skimmer, 4 returns (2 therapy jets in steps), Hayward pool vac ultra, Hayward Heat Pro heat pump, non-curved pool slide, 6' jump board, 12 ml clear solar cover, TF-100 test kit, added salt for feel 1,250 ppm, we had "pink algae" in 2010.
    Winter: Hot Springs Vista Spa, 500 gallons. Using BBB method for the first time and for the first time in ages, the water is crystal clear

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    Join Date
    Jan 2009
    Cupertino, CA

    Re: CYA - Myth or could it be?

    You might try the simultaneous drain/refill procedure described here, to avoid exposing the plaster:

    As long as where you pull water from is "as far as possible" from where you're adding water, and you can keep the rates balanced, it oughta work.
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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    Isaac-1's Avatar
    Join Date
    May 2010
    SW Louisiana

    Re: CYA - Myth or could it be?

    Keep in mind that cold water sinks and warm water rises, in case your fill water is warmer or cooler than your pool.

    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from
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