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Thread: CYA low but FC ok

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    CYA low but FC ok

    My cya is low (about 35) but my free chlorine is ok at 5. If I raise the cya, that will cause my cya to spike. My question....if fac is holding, do I need to raise cya?
    15k gallon roman gunite w pebble finish. Cartridge
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    Richard320's Avatar
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    Re: CYA low but FC ok

    I'm not sure I understand. By chance, do you have a SWG? If not, 35 is fine for the CYA. It leaves plenty of room to use trichlor pucks if you go away for a few days.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    JoyfulNoise's Avatar
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    Re: CYA low but FC ok

    As long as you maintain proper FC/CYA ratio then the absolute CYA level only affects chlorine loss due to sunlight. Therefore, if your daily chlorine loss rate, as measured by how much chlorine you need to add to maintain the proper FC, is acceptable to you, then your CYA is fine where it is.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    JoyfulNoise's Avatar
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    CYA low but FC ok

    But I will add that, if you are manually dosing chlorine, then you should be measuring your FC in the evenings and adding chlorine in the mornings. You want to make sure your FC is at the right level when your sun is getting the highest heat and sun exposure.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: CYA low but FC ok

    According to the OP's signature there is a SWG in use. First, the pool is fine with the FC/CYA ratio as it is, but you might not be maximizing the lifespan of the SWG cell. How much sun does the pool get?

    For a normal SWG pool we recommend the CYA to be 70-80 and don't let the FC drop below 4 ppm. This ratio actually helps to maximize the cell life because less chlorine is burned off from the sun. With your current numbers the CYA level will lead to more chlorine being lost from the sun.
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    Test Kits . Pool Math . Chlorine/CYA Chart . The SLAM Process

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    borjis's Avatar
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    Re: CYA low but FC ok

    Quote Originally Posted by JoyfulNoise View Post
    But I will add that, if you are manually dosing chlorine, then you should be measuring your FC in the evenings and adding chlorine in the mornings.
    but you need the FC measure/test to know how much chlorine to add...why not just add it after testing?
    That's what I usually do since a properly maintained pool will lose little to zero fc over night
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
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    JoyfulNoise's Avatar
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    Re: CYA low but FC ok

    Quote Originally Posted by borjis View Post
    but you need the FC measure/test to know how much chlorine to add...why not just add it after testing?
    That's what I usually do since a properly maintained pool will lose little to zero fc over night
    As you said, properly cleaned water will have no lose overnight, so if I manually dosed (which I'm glad I don't, I have an SWG), I would just do it in the AMs

    It's a moot point anyway, the OP runs an SWG.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: CYA low but FC ok

    Thanks all.

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