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Thread: CYA Question

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    Join Date
    Jul 2014

    CYA Question

    If our CYA is in between two levels at 35--how do we calculate our target FC/shock FC/minimum FC? I was adding the two variables and then dividing--is this accurate? Also, our CC has been at 0.4-- from what I have read on TFP it should be no more than 0.5--is the 0.4 too close, should we be trying to lower this?

    Thanks-- feeling a little less overwhelmed!

    16,500 gal, IG plaster, restoration January 2014; 1 HP Energy Flo pump, 48 sqft DE filter-Hayward ProGrid 4820, 360 Polaris Sweeper; Taylor Complete K2006 FAS-DPD; Timer

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    Mod Squad JohnT's Avatar
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    Apr 2007
    SW Indiana

    Re: CYA Question

    You can approximate your levels by interpolating where your CYA is between the levels on the chart. You are halfway, so your min would be 2.5, target 4.5 and shock 14ppm. The CYA test isn't really accurate enough to worry about it though.

    Your CC is fine. Dont sweat it!
    TFP Moderator
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    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Central Minnesota

    Re: CYA Question

    The ranges of FC for a given CYA level are 7-12%. So take the CYA level and multiply by 0.07. That's your minimum FC. Always round that number up. The reason you always round up (even 4.2 should be 5, for example) is that precision of daily color match TC testing isn't very precise and the CYA test itself only has a resolution of 10 ppm. A more pragmatic and cautious approach to eliminate chances of problems is to round up when calculating.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Donldson's Avatar
    Join Date
    Jun 2009
    NW Ohio

    Re: CYA Question

    Seems like we are over complicating this a bit. Especially since the CYA test isn't all that precise.

    If your CYA test is showing between the 30 line and the 40 line, round up to 40. Then follow the chart for 40 (minimum FC 3, try to keep it around 5). Keep it simple.

    CC of .4 is entirely acceptable. No need to even measure that precisely. A 10 ml sample works just fine, any CC below 1 is typically ok unless there are other factors involved (excessive FC loss, strong chlorine smell, cloudy water, etc).
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
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    Richard320's Avatar
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    Jan 2010
    San Dimas, CA (LA County)

    Re: CYA Question

    If you just plug whatever CYA number you have into pool math, and set up the suggested levels at the bottom of the table, the second to the last box will give you shock level.
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    Mod Squad jblizzle's Avatar
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    May 2010
    Tucson, AZ

    Re: CYA Question

    To be totally accurate, only one drop of reagent for the CC test is really acceptable. So, if you are using 25ml water sample, the CC should be no more than 0.2ppm. Just keep an eye on it at this point.
    Jason, TFP Moderator
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