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Thread: FC / CYA Relationship

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    Join Date
    Nov 2015
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    FC / CYA Relationship

    Hi All,

    I'm really learning heaps on this forum - it's great following some of the threads! Now that I've been using my K-2006C for a while now, I'm starting to get some more meaningful results. Latest results are:
    FC = 8ppm
    CC = 0
    pH = 7.8 - constant battle keeping this down...
    TA = 80
    CH = 280
    CYA = 80

    Since if now got my CYA up to where I need it, it seems that (with all things being equal) my FC result has almost doubled. Is that to be expected?
    I'm assuming so, given the improved sun protection, but just wanted some thoughts.

    Thanks again!
    60,000 litre (16,000gal), IG, Pebble, Cartridge Zodiac CS150, Haywood Super II Pump, SWG, Zodiac Robotic CX20, K-2006C Test Kit

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    Mod Squad kimkats's Avatar
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    Tallahassee, FL
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    Re: FC / CYA Relationship

    NICE! Your CYA is acting as sunscreen for you FC. Nice huh?

    If your PH is giving you fits try lowering your TA a bit at a time to see if your pool would like it lower and be better behaved.

    Pool School - Lower Total Alkalinity

    We have found every pool is different and has a different sweet spot. Now is the time for you to adjust your levels for your pool. The TFP guidelines are just that...........guides to give you a starting point.

    I hope this helps.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Texas Splash's Avatar
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    Re: FC / CYA Relationship

    That is a good sign. Now if your FC continues to build much higher than your target FC of 6, you can always consider reducing the % output or run-time of your SWG so it's not working quite as hard. That's the good thing about having the CYA at 70-80. Enjoy your swimming season.
    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
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    Divin Dave's Avatar
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    Longview, Texas
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    Re: FC / CYA Relationship

    Right. THe higher CYA is protecting the FC, so it lasts longer.
    Like Splash says, if your FC continues to climb, then either lower the % output on the SWG or shorten the run time.

    It will take a litle trial and error to get it just right......
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
    www.tftestkits.net Experience- it's what's learned just after you needed it most !!

  5. Back To Top    #5

    Join Date
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    Re: FC / CYA Relationship

    you said "my FC result has doubled", I'm interpreting that to mean that when you test for FC, your results are twice as much, numerically, than before. Like you used to get a reading of 4 on older FC tests.

    Basically yes, because you have that much CYA stabilizer in the pool, you need a higher amount of FC (and it's why you need a drop test for chlorine, to read over 5). However, almost all of that Free Chlorine is not "free", it is attached to the CYA and NOT ACTIVE. Using the CYA chart to keep your levels where the chart recommends, you will have the same amount of ACTIVE CHLORINE in your pool as someone with, roughly, 40 CYA and a FC reading of 4. You will not USE UP chlorine any faster, and will actually use chlorine slightly slower due to some additional UV shielding that has been observed at higher CYA levels.
    10,500 gal IG, Topaz Pebble, auto-level
    Hayward DE filter, 2HP Ecostar VSP, ProLogic PS-4, GVA actuators
    Cal Pools Wave Force Plus (wall return jets plus 2 floor pop-ups), Venturi Skimmer
    Water sheer, 2 wok pots, bubbler stem on the baja step
    ColorLogic Mutlicolor LED lamp. Taylor 2006+speed stir

  6. Back To Top    #6

    Join Date
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    Hunters Hill, Sydney, Australia
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    Re: FC / CYA Relationship

    Thanks for all the tips - looks like I need to work on getting the TA down a bit.
    60,000 litre (16,000gal), IG, Pebble, Cartridge Zodiac CS150, Haywood Super II Pump, SWG, Zodiac Robotic CX20, K-2006C Test Kit

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