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Thread: Crystal clear pool to green overnight

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    Crystal clear pool to green overnight

    Last night my pool was crystal clear. Just letting chlorine drift after a slam. Here are readings:

    FC: 10.5
    cc: 0
    ta: 145
    cya: 80
    Ph: 7.5

    we had a lot of rain last few days and woke up today and pool is nearly to the top and a cloudy green. What can this be and how can i fix this? (I am hoping not having to slam)
    36,000 Gallon, 40x20 IG, Vinyl, Hayward S- 200 Sand Filter, 300,000 MasterTemp heater, 1hp Superpump, Polaris 9550 sport, TF100 test kit

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    Texas Splash's Avatar
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    Re: Crystal clear pool to green overnight

    Well, the only thing I can see is that based on your CYA, your pool is struggling to maintain proper FC sanitation even though you have your FC elevated just above the target of 9. I can't help but wonder if your CYA isn't actually a bit higher which would indicate why the chlorine is struggling once you let it start to drop. Remember there is a +/- 15 ppm variance on that CYA test. Unfortunately, I don't see any other option but to SLAM. But first, I would consider a partial water exchange to lower that CYA (even to at least 60) and ensure there is nothing being added to the water (i.e. tablets, bags of shock, etc) that may increasing CYA without your knowledge.
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    Re: Crystal clear pool to green overnight

    I am noticing the debris all around pool edge which tells me the pool water went over the edge.

    - - - Updated - - -

    I am draining now because of water level so i will keep draining from main drain and exchange water. Thanks for reply
    36,000 Gallon, 40x20 IG, Vinyl, Hayward S- 200 Sand Filter, 300,000 MasterTemp heater, 1hp Superpump, Polaris 9550 sport, TF100 test kit

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    Re: Crystal clear pool to green overnight

    image.jpgBump... Any ideas why this would happen? I cant see it being algae because my FC was dropping very very slowly so cant imagine it was attacking anything. I raised it to 15 and it is still not dropping (cloudy) day
    36,000 Gallon, 40x20 IG, Vinyl, Hayward S- 200 Sand Filter, 300,000 MasterTemp heater, 1hp Superpump, Polaris 9550 sport, TF100 test kit

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    Mod Squad YippeeSkippy's Avatar
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    Re: Crystal clear pool to green overnight

    If it came on so quickly, I would assume that the SLAM would proceed just as quickly. The longer you wait the more time algae will have to grow.

    I notice your CYA is pretty high- do you use a SWG? Other wise I would recommend you drain 1/2 and refill then SLAM-away!
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
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    Re: Crystal clear pool to green overnight

    Quote Originally Posted by YippeeSkippy View Post
    If it came on so quickly, I would assume that the SLAM would proceed just as quickly. The longer you wait the more time algae will have to grow.

    I notice your CYA is pretty high- do you use a SWG? Other wise I would recommend you drain 1/2 and refill then SLAM-away!
    I did drain half and refilling now. The thing is i understand how to fix it, i want to know why it happened? I know it may be impossible to say since you werent at my house during the massive rainfall (2.5" in 4 hours).. This amount of rain is really rare but if i am going to have to slam after every rainfall i will keep the pool closed until late may
    36,000 Gallon, 40x20 IG, Vinyl, Hayward S- 200 Sand Filter, 300,000 MasterTemp heater, 1hp Superpump, Polaris 9550 sport, TF100 test kit

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    Richard320's Avatar
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    Re: Crystal clear pool to green overnight

    By chance is there a lawn near the pool? Could runoff make it from the lawn to the pool? If it's been fertilized recently, there's your answer.
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    Re: Crystal clear pool to green overnight

    Quote Originally Posted by Richard320 View Post
    By chance is there a lawn near the pool? Could runoff make it from the lawn to the pool? If it's been fertilized recently, there's your answer.
    If it did overflow yes lawn chemicals could be it. This is what i thought but hasnt been fertilized for a few weeks. Either way i am lowering the CYA and starting slam process. Just need to keep a better eye on levels and close cover when that amount of rain is predicted
    36,000 Gallon, 40x20 IG, Vinyl, Hayward S- 200 Sand Filter, 300,000 MasterTemp heater, 1hp Superpump, Polaris 9550 sport, TF100 test kit

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