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Thread: Green Algae Keeps re-appearing

  1. Back To Top    #1

    Join Date
    May 2007

    Green Algae Keeps re-appearing

    I keep shocking with liquid chlorine but the green Algae keeps coming back. Right now the pool is clear but when I get home from work there is Algae on everything lightly and some thick bunches in spots. Any recomendations on what to do?

    20*40 Liner pool with 8.5 foot diving end (Think it's about 25K)
    Saltwater with filter now on 24Hrs with generator set at 60%

    Before adding anything tonight these were my readings:
    FC 5
    CYA 50
    PH 7.8
    TA 210
    CH 290
    Water temp is 82

    I added 1.5 gallons of 10% chlorine and .5 gallons of Muratic acid
    20*40 Liner 2'-8' deep, Spill Over SPA, Electric Cover, Jandy Purelink (Aquapure & PDA), Hayward SP2610x15 (1.5HP Single Speed), Hayward H300 (Millavolt)

  2. Back To Top    #2
    Butterfly's Avatar
    Join Date
    May 2007
    South Carolina

    Re: Green Algae Keeps re-appearing

    It does not sound like you are reaching shock level based on your CYA level.

    What test kit are you using?

    Do you use Jason's Pool Calculator for dosing? (link in my sig)

    Shock level for your CYA of 50, is between 16 & 20. Adding 1.5 gallons (192 ozs) of 10% bleach will raise your FC by 6ppm, assuming 25K pool. If your FC was 6 ppm when you tested and added the 1.5 gallons, you would now have only 11ppm FC which is still NOT shock level.

    I suggest you see the Pool School articles on "Defeating Algae" and "How to Shock Your Pool".
    Let us know if you have any q's. Lots of folks around to help.
    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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  3. Back To Top    #3

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Green Algae Keeps re-appearing

    I suggest you see the Pool School articles on "Defeating Algae" and "How to Shock Your Pool".
    Double ditto!!. Shcok according to the process described in Pool School and your algae will be gone.

    FWIW, if your pool is 20'x40' with a diving end, you have a lot more than 25,000 gallons....closer to 35-38k
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Green Algae Keeps re-appearing

    If the algae tends to come back in the same place, then perhaps circulation is poor in that area. Try pointing returns in a somewhat different direction. You can also measure the FC near the area of algae growth as that is probably the lowest FC point in the pool. Also, be sure to brush the pool, especially where algae is present, and not just shock -- one has to get rid of any biofilm that has formed and brushing helps with that.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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