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Thread: First time ever saw some slight green patches on the bottom

  1. Back To Top    #1

    Join Date
    May 2010
    Location
    New Orleans, LA
    Posts
    20

    First time ever saw some slight green patches on the bottom

    Here's are my numbers and situation:

    SWG pool - above ground.

    Salt 3100
    FC 6.0
    CC 0.5
    TC 6.5
    CYA 55
    TA 60
    pH 7.65

    It was a very hot, sunny week and FC dipped as low as 3.5 one day. It was harder to raise it than I thought it would be since it dipped that low.

    I cleaned the cartridge filter today, then I brushed the green stuff so it turned the water a little cloudy around it. But it's mostly still relatively clear. Obviously I need to up the CYA, but don't want to do that if I need to shock it. Upping the CYA should also bring the pH down a bit to its usual 7.5 level.

    Should I Shock or up the CYA? If I up the CYA, should I raise the FC even higher? I'm usually around FC 6.0 and CYA 70.

    I'm guessing I should probably just let it filter overnight (which I don't usually do), check the water in the morning, and add some CYA if all looks good. Right?
    15'x30'x54" oval AG; 12,500 gallons; Aquatrol SWG; Cartridge filter; 2-speed, 2-HP pump; 2 return jets

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: First time ever saw some slight green patches on the bottom

    You should shock if you have visible algae. If it is just a couple of patches, then one night at shock level plus brushing the pool will usually take care of it, though it might be a bit more than that. Raise CYA after you are done shocking.
    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

    Join Date
    May 2010
    Location
    New Orleans, LA
    Posts
    20

    Re: First time ever saw some slight green patches on the bottom

    Oops. I hadn't gotten a response so I went ahead and hit the pool with CYA and upped the chlorine just a bit to 7.5. The green patches returned. Fortunately, I read that it takes up to a week for CYA to get saturated into the water so I shocked it with bleach tonight and turned the SWG on Super Chorinating (the highest chlorine production setting).

    Here's my new question. Presuming I've knocked it out with this, won't I be left with a pool with a chlorine level of 25 or so? How do I get it to a swimmable level of chlorine? More importantly, WHAT IS A SWIMMABLE LEVEL? Do I get it there by turning off the SWG and just letting it come down?
    15'x30'x54" oval AG; 12,500 gallons; Aquatrol SWG; Cartridge filter; 2-speed, 2-HP pump; 2 return jets

  4. Back To Top    #4
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: First time ever saw some slight green patches on the bottom

    Yes, turn off the SWG until it drops down to normal (you have to turn it off to do an overnight FC loss test which you should do in this instance anyway.)

    Anything up to shock level is safe for swimming...
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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