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Thread: why CYA 70

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    Join Date
    Sep 2016
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    tullahoma
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    why CYA 70

    SWG, 220000 gal ,2 1/2 hayward pump ,cartridge filter, t cell 15...new to site!
    why is it recommended to keep CYA at 70 if it gobbles up Chlorine, makes my swg work harder and needs a higher FC to stay "healthy"?
    marty f

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    Mod Squad JohnT's Avatar
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    Re: why CYA 70

    Welcome to TFP!

    You have it backwards. CYA protects chlorine from UV degradation which makes it easier for your SWCG to maintain the chlorine level. Though higher CYA levels require higher FC levels for sanitation, the CYA reduces the chlorine used up by sunlight meaning you typically add less chlorine to the pool with high CYA levels unless you get algae and need to SLAM.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Mod Squad Texas Splash's Avatar
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    Jun 2014
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    South-Central Texas, Marion/San Antonio
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    Re: why CYA 70

    Hello and welcome to TFP! Actually, it's the other way around. The additional CYA level "protects" the valuable chlorine generated by your SWG so it can maintain the proper FC level more efficiently. At lower CYA levels, the sun will grab your FC faster than desired resulting in higher run times/percentages.

    John beat me to it.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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