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Thread: CYA and Chlorine

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    CYA and Chlorine

    I have seen a few times on the website where it says FC should be 7.5% of cya. Per the target level on the CYA chart in pool school, it shows at 40 CYA to have a target of 5, which is around 12.5%. Have I read into this wrong or what is the amount of FC with a given CYA?

    Thanks.
    13,000 Plaster IG Pool approx
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    Emerson 1081 EB653 1.0 HP 1.40 S.F. 3450 RPM
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    Mod Squad Bama Rambler's Avatar
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    Re: CYA and Chlorine

    If you look at the chart you'll see that for a CYA of 40 the minimum FC level is 3 which is 7.5% of the CYA level. Now the target is at a level so that given normal 2 ppm loss during the day will still leave you with a FC level of 3. If you tried to maintain a level of 3 there would be times when it'd get away from you and drop below that and leave you open to algae or worse.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: CYA and Chlorine

    Quote Originally Posted by Bama Rambler
    If you look at the chart you'll see that for a CYA of 40 the minimum FC level is 3 which is 7.5% of the CYA level. Now the target is at a level so that given normal 2 ppm loss during the day will still leave you with a FC level of 3. If you tried to maintain a level of 3 there would be times when it'd get away from you and drop below that and leave you open to algae or worse.
    Got you thanks for explaning. So the min is incorporating the FC loss during the day?
    13,000 Plaster IG Pool approx
    Hayward C5030 Cart Filter
    Emerson 1081 EB653 1.0 HP 1.40 S.F. 3450 RPM
    Pool Calculator, Pool School, TF Test Kits

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    Mod Squad Bama Rambler's Avatar
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    Re: CYA and Chlorine

    The min is what you never want to go below. The target incorporates the normal loss during the day so you'll always be at or above the min.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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