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Thread: Very green pool

  1. Back To Top    #1

    Join Date
    Jun 2015
    Lexington, SC

    Very green pool

    So we were out of town, pool turned green, cleared it up but during the week of recovery it started to turn green again so I tried just keeping the chlorine levels high like you're supposed to and it wasn't working. But the weird thing is I was maintaining chlorine levels overnight so not sure why it was still trying green.

    When I first started battling the algae after vacation everything was good except ph was as low as it will read and cya was a tad low. I think this was my first mistake, I raised both after the green went away to try and maintain chlorine levels. However cya has maintained pretty steady at 100 (again, odd?) but ph went Up though is down to about 7.8 now.

    Ta is normal and I've been keeping fc and tc levels high to no avail. So (2nd mistake) I have tried shock (both trichlor and dichlor at seperate times) which I think is what messed up ph. I even tried algaecide.

    I've battled algae successfully before so I'm trying to figure out what I'm doing differently/wrong.

    5000gallon above ground pool, brought temp down to around 80 as it was quite warm, sand filter

  2. Back To Top    #2
    Mod Squad Texas Splash's Avatar
    Join Date
    Jun 2014
    South-Central Texas, Marion/San Antonio

    Re: Very green pool

    Hello and welcome to TFP! Well, while it appears you have been trying to remedy your pool with some pool store methods of shock and algaecides, they are not what you will find used here at TFP. There is one basic flaw resulting in your green water - your chlorine and stabilizer (CYA) levels are not aligned as designed by the Pool School - Chlorine / CYA Chart.

    To fix your water you will need to "SLAM" via the Pool School - SLAM - Shock Level And Maintain. But before you can SLAM, you need to stop using pool store powders or shock, and tablets/pucks as they are contributing to your already high CYA level. The only way to reduce your CYA is to do partial drain. Assuming your CYA is only 100 (it could be more), you will need to drain at least 50% of your water to bring the CYA down to about 50 ppm. Only then can you do a SLAM in a manageable fashion.

    Also, you will need your own test kit (TF-100 or Taylor K-2006). Do you have one? If not, you can get one of them at

    To summarize:
    1 - Partial drain to lower CYA to about 50
    2 - Adjust pH to 7.2 before starting the SLAM
    3 - Start a SLAM

    But you will need the test kit to accurately read FC at the higher level required. If you have more questions or concerns, please let us know.

    - - - Updated - - -

    Oh, and don't add any more algaecides as they tend to add metals (copper) to your water.
    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
    If you enjoyed your TFP experience, please consider donating to Support TFP!

  3. Back To Top    #3
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    DFW, TX

    Re: Very green pool

    It sounds like you are using test strips to test. They are wrong more than the weatherman. You are chasing a squirrel trying to balance your water with test strips. The only thing worse than test strips is pool store tests. Get a good test kit, read the Pool School - ABCs of Pool Water Chemistry and really take control of your pool.
    TFP Moderator
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