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Thread: SLAM question

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    rabbet's Avatar
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    SLAM question

    I'm on the on the fourth day and realize I've made several mistakes. Here are the readings from day one:
    pH 7.7 (first mistake)
    FC 4
    CC <.5
    TA 90
    CYA 30
    CH 275

    I think I should have lowered the pH, but it's too late now.

    I had persistent algae, which I assumed was mustard because it was there in spite of correct chlorine and pH levels. It congregates along seams and crack repairs, both of which are a bit rough, and at the right angle corners where the sides meet the floor. So I used the MA number for the SLAM which was 19 ppm, instead of the shock number which would have been 12. So the question is, should I lower the FC to 12 and continue until the FC holds overnight, and then raise the FC to 19 for 24 hours after that? The water is already clear and today the CC was 0 for the first time. I do notice there is a brief white cloud when I brush. Is that dead algae or live algae? I also realized yesterday that I hadn't left the poles, brushes, etc in the pool.

    I'm also wondering if it's foolish to go through all this right before closing the pool.

    I'd appreciate any guidance.
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

  2. Back To Top    #2
    Mod Squad tim5055's Avatar
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    Re: SLAM question

    Quote Originally Posted by rabbet View Post
    I'm on the on the fourth day and realize I've made several mistakes. Here are the readings from day one:
    pH 7.7 (first mistake)
    FC 4
    CC <.5
    TA 90
    CYA 30
    CH 275

    I think I should have lowered the pH, but it's too late now.

    I had persistent algae, which I assumed was mustard because it was there in spite of correct chlorine and pH levels. It congregates along seams and crack repairs, both of which are a bit rough, and at the right angle corners where the sides meet the floor. So I used the MA number for the SLAM which was 19 ppm, instead of the shock number which would have been 12. So the question is, should I lower the FC to 12 and continue until the FC holds overnight, and then raise the FC to 19 for 24 hours after that? The water is already clear and today the CC was 0 for the first time. I do notice there is a brief white cloud when I brush. Is that dead algae or live algae? I also realized yesterday that I hadn't left the poles, brushes, etc in the pool.

    I'm also wondering if it's foolish to go through all this right before closing the pool.

    I'd appreciate any guidance.
    I would say the stuff you are seeing when you brush is either dead algae or dirt/pollen/plaster dust.

    If you have brushed well and don't see algae in the seams like before do an Overnight FC Loss Test (OCLT) to see if you can end the SLAM. The issue of not lowering the pH and conducting the SLAM at MA levels the whole time are water under the bridge.

    Nope, do it now so it's not a bigger problem in the spring.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    pwrstrk's Avatar
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    Re: SLAM question

    If your seeing algae in those areas it could be from poor circulation in those areas. Might try brushing there more often.
    I think your ready to try an OCLT. 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    rabbet's Avatar
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    Re: SLAM question

    Strangely, the place where I see the algae is where there is the most circulation.
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

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    pwrstrk's Avatar
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    Re: SLAM question

    What is your normal FC target level ?
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    rabbet's Avatar
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    Re: SLAM question

    FC 4

    - - - Updated - - -

    Quote Originally Posted by tim5055 View Post

    If you have brushed well...
    I never think my brushing is adequate.
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

  7. Back To Top    #7
    pwrstrk's Avatar
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    SLAM question

    For the CYA level of 30 you should target 5-6. That's a little more room so you don't fall below 2. You may have dipped to low with your FC and a little algae starts to form, but you keep it from a full blown outbreak.
    When you open next year I'd go with a CYA level of 40 and target your FC level at 7 and never below 3. 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

  8. Back To Top    #8
    rabbet's Avatar
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    Re: SLAM question

    Quote Originally Posted by pwrstrk View Post
    For the CYA level of 30 you should target 5-6. That's a little more room so you don't fall below 2. You may have dipped to low with your FC and a little algae starts to form, but you keep it from a full blown outbreak.
    When you open next year I'd go with a CYA level of 40 and target your FC level at 7 and never below 3. ��
    I was going by the chlorine/CYA 'Best Guess' chart and Chemgeek's chart.
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

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    pwrstrk's Avatar
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    SLAM question

    Pool Math will suggest different levels that I use in my pool. Never had algae at anytime. My CYA level is 40 and I target FC at 7. That gives me 4ppm wiggle room from FC burn off and swimmers so I don't fall below my min level of 3. 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    BoDarville's Avatar
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    Re: SLAM question

    I follow the same process as pwrstrk. During the summer swim season, I target the high end of the FC range suggested by PoolMath . Between sunlight and the warmer water temperatures and higher bather loads of summer, the extra headroom provided by maintaining FC at the upper end of the recommended range has kept my pool algae-free. Haven't had to shock/SLAM in I don't know how many years.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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