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Thread: algea again

  1. Back To Top    #1

    algea again

    over a week my pool went from sparking clear to increasingly hazy. then I started to see green algea on the bottom. I have been diligent on keeping my levels correct. (FC between 2 and 6)
    Last nights test
    FC 5.0
    CC O.O
    PH 7.5
    CYA 50
    ta 110

    pool calc said shock level is 16 and to add 160 oz of 12% shock. that took me to 21 and held it for two hours, CC still tested at 0.0. I could not retest till this evening due to work but I ran the filter for 24 hours. this evening the water looks much better but still some green stuff on the bottom.
    Tonights test. shows FC at 9.0 and CC 0.0 PH held at 7.5.

    What I dont understand is the CC being zero.
    also I was only running the filter for 8 hours a day and had not backwashed for about 3 weeks since the flow was still good.
    I have many friends and family in the area with pools and they do not have the frequent problems I do. They keep the PH right and add chlorine Nightly. The difference is they all have DE filters and I am running sand.
    24 X 52Ěround, Vinyl AGP, 150 lb Sand 1.5 hp filter

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: algea again

    With CYA at 50, for day to day use you want FC between 4 and 8, and never below 4. If you allowed FC to go down to 2, that was too low.

    CC at zero is common enough. There isn't always any CC, even when there is a full fledged algae bloom in progress.

    This doesn't have anything to do with having a sand filter, it is about consistently maintaining the correct FC level.

    You should be brushing the entire pool every day while at shock level.
    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
    Butterfly's Avatar
    Join Date
    May 2007
    South Carolina

    Re: algea again

    I have been diligent on keeping my levels correct. (FC between 2 and 6)
    I think this may be the culprit FC values for 50 CYA are between 4 & 8, and never below 4.

    Continue to shock until you meet the three criteria to be done shocking (red lines in my sig).
    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.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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  4. Back To Top    #4

    Re: algea again

    Water is crystal clear, pool looks good, but still seeing light algea where wall meets bottom, only visible to me because I know where too look. Some dead algea still evident on the bottom. I only need to vacuum about 1x / week and backwash about every 2,
    Latest numbers

    FC 4.0
    CYA 45
    TA 80
    ph 7.2

    Adding about 2 ppm of 48% cal hypo per day
    PH needs lowering about 1x / week. I think the water looks clearer with the ph closer to 7.2 than 7.8.

    Any suggestions?
    24 X 52Ěround, Vinyl AGP, 150 lb Sand 1.5 hp filter

  5. Back To Top    #5

    Join Date
    Aug 2010
    Boston, MA

    Re: algea again

    Have you done an OCLT?
    20k gallon IGP
    Plaster over gunite
    3/4 hp Hayward pump
    Purex Triton DE filter
    TF100 test kit w/ speedstir

  6. Back To Top    #6

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: algea again

    Any suggestions?
    The visible presence of algae means you should shock the pool.....according to the VERY specific directions in Pool School. Continue to shock the pool until algae is no longer visible and you pass the is really that easy!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  7. Back To Top    #7

    Re: algea again

    About 2 weeks ago I shocked and passed the ONFC test with no CCs.
    I am going to shock again
    24 X 52Ěround, Vinyl AGP, 150 lb Sand 1.5 hp filter

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