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Thread: CYA and FC usage

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    Join Date
    Jun 2013
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    Middlesex County/VA
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    CYA and FC usage

    I had been having some trouble with FC losses of 3.5 to 5.5 ppm a day. My pool is in full sun from 10 am to 5 pm. My reading on my CYA test appeared to be between 40 and 50 then. After posting my issues I decided to add a bit more stabilizer a few weeks ago. I now am seeing 2 to 3 ppm drop per day. I tested my CYA this morning and it is between 60 and 70. I have trouble determining seeing the black dot lol. I have been targeting FC at 5 to 5.5. Should I be upping my FC even though I am having no troubles?

    This mornings readings
    FC 2.2
    CC 0
    PH 7.6
    TA 90
    CYA 60 to 70
    Pool Size: 24' Lomart Whispering Wind II 13000 gallons
    Pool Type: Aboveground
    Pump:Hayward 1 1/2 HP Power Flo Matrix 2 Speed
    Filter: Hayward S230T 250lb Sand Filter

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    JasonLion's Avatar
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    Silver Spring, MD
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    Re: CYA and FC usage

    Your FC level is too low. With CYA at 60 to 70 you want FC to be between 5 and 10 and never below 5.

    It is difficult to tell for sure, but one possible cause of excess chlorine consumption is a low level algae problem. I recommend doing an overnight FC loss test to verify that there isn't anything using up chlorine other than sunlight.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

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    Re: CYA and FC usage

    My over night FC loss is between .5 and 1 ppm
    Pool Size: 24' Lomart Whispering Wind II 13000 gallons
    Pool Type: Aboveground
    Pump:Hayward 1 1/2 HP Power Flo Matrix 2 Speed
    Filter: Hayward S230T 250lb Sand Filter

  4. Back To Top    #4
    JasonLion's Avatar
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    Re: CYA and FC usage

    Then I guess that is normal for your CYA level.

    You might want to read over the Notes section in this post about how to do the CYA test.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  5. Back To Top    #5

    Join Date
    Feb 2014
    Location
    Phoenix, AZ
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    51

    Re: CYA and FC usage

    One other suggestion since your CYA level is getting to the point where this help - is to run the test at half strength and see what result that gives you. Jason says to only do that at 90 or above, but it helped me isolate my CYA level and I'm down at 60(ish).
    From
    CYA Extended directions
    9. If your CYA level is 90 or higher, repeat the test adjusting the procedure as follows:
    Fill the mixing bottle to the lower mark with pool water.
    Continue filling the mixing bottle to the upper mark with tap water.
    Shake briefly to mix.
    Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
    Continue the test normally from step 3, but multiply the final result by two.
    20k IG PebbleTec w/ STA-RITE PE5E-182L 1HP and Zodiac Polaris PB4 for Polaris 380 vacuum / Hayward ProGrid DE4820 Filter / TF-100 but I havent broken down and gotten a speed stir yet

  6. Back To Top    #6

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    Jun 2013
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    Middlesex County/VA
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    Re: CYA and FC usage

    After trying the extended test it is reading about 65 to 70 on the CYA. Should I try to drop down some or just keep going as I am. My overnight drop was 1.0 and with a partly cloudy day yesterday it only dropped 1.5. my average daily drop is about 3.0
    Pool Size: 24' Lomart Whispering Wind II 13000 gallons
    Pool Type: Aboveground
    Pump:Hayward 1 1/2 HP Power Flo Matrix 2 Speed
    Filter: Hayward S230T 250lb Sand Filter

  7. Back To Top    #7
    JasonLion's Avatar
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    May 2007
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    Re: CYA and FC usage

    Your daily FC loss is already on the high side. I would leave things as they are, rather than lower CYA.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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