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Thread: help,. can't keep fc at frequent levels

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    help,. can't keep fc at frequent levels

    FC = 3.5
    CYA = 50
    PH = 7.5

    I put in 2 bottles of bleach last night at around 9pm. After leaving filter on for half hour, FC = 10. This morning, FC = 3.5 around noon. This has been happening on a daily basis after putting in 2 bottles of bleach. Any help will be appreciated.

  2. Back To Top    #2
    Ohm_Boy's Avatar
    Join Date
    May 2007
    Orlando, FL

    Re: help,. can't keep fc at frequent levels

    I'm pretty confident that you have algae. Basically, there are two things that make your free chlorine go away - Sunlight (UV) and organics (in this case, algae). If you lose chlorine at night, when no sun is on your pool, you are losing it to something organic.

    With a CYA level of 50, you shouldn't let your FC level drop below 4, and should keep it at 6.
    So what's happening is that an early stage algae bloom is consuming your chlorine. The fix is more chlorine.

    To get rid of your algae, you need to raise your FC level to 20 using liquid chlorine (bleach) and maintain it there until the FC reading will maintain overnight with no more than 1ppm loss.
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

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    h2ctpdjl's Avatar
    Join Date
    Jul 2008

    Re: help,. can't keep fc at frequent levels

    You mentioned your test was done around noon today. Unless you had complete cloud cover, or your pool was in total shade, the sun could have contributed to some of the loss of your FC level, though I wouldn't think it would have been 6.5ppms since last night. In order to have accurate FC test results, you should do it before the sun hits your pool water. I too, tend to think algae.
    18,000 gal, 18x32 IGP, vinyl liner, 3 to 5.5ft depth. One inlet/skimmer (Aqua Genie), one main drain. Hayward Pro Series Sand Filter w/filtration rate of 20 GPM/FT, Two-Speed Pentair Whisperflo 1 HP pump, Natural Gas Hayward H200 pool heater, Aquabot T2 (200 Series) Robotic Pool Cleaner (my best friend), Automatic Electric Pool Cover (2nd best friend).

  4. Back To Top    #4

    Re: help,. can't keep fc at frequent levels

    Thank you both for the quick response. I will shock it tonight and keep fc to 20 until I see the 1 ppm loss. Also, for best results bleach should be added after the sun goes down correct?

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: help,. can't keep fc at frequent levels

    Here's the indications of how to know when your done shocking.
    1) Your overnight chlorine loss is less than 1ppm. And
    2) Your CC's are .5 or less. And
    3) Your water is clear.

    During the shocking process you should add chlorine often enough that your FC level never goes below you target level. This may require testing and adding chlorine several times a day. i.e. Your target is 20 and you test and add chlorine in the morning, you should test again in a few hours to ensure you're still at target level.
    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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  6. Back To Top    #6

    Re: help,. can't keep fc at frequent levels

    Thank you everyone for your help.

    ok, so I have been testing and adding chorline for the last 4 hours. The FC has been dropping consistently every hour.

    Shocked pool at 5:45 w/ 4 gallons of bleach and CYA is 50, very close to 40 though.

    tested about every hour after that, here are the results:

    6:50: FC 18 - added 1 gallon
    7:50: FC 19 - added 1/2 gallon
    8:50: FC 16 - added 1 gallon

    I def agree I have an algae problem.

    On average, how long does it take to clean up a problem like this?

    I am going to keep plugging away through out the night to see if I can have it solved by the morning.

    FWIW, My pool has also been clear the whole time I have had rgis problem.

  7. Back To Top    #7
    Butterfly's Avatar
    Join Date
    May 2007
    South Carolina

    Re: help,. can't keep fc at frequent levels

    On average, how long does it take to clean up a problem like this?
    Since your pool has been clear the whole time, probably not too long.
    As Ohm_Boy mentioned, probably an early stage bloom. Do you know your CC test number?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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  8. Back To Top    #8

    Re: help,. can't keep fc at frequent levels

    Continuation of results:

    10:10 - 17, added 1 1/2 bottles of bleach.
    11:20 - 20, added half bottle of bleach.
    12:20 - 16, added bottle of bleach.
    1:20 - 19.5, CC = 1, added no bottle of bleach.

    In addition, I have a cartridge filter that I am going to clean out tomorrow as well.

    Thank you again for everyones input.

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