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Thread: When to SLAM as opposed to just adjust FC to target?

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    When to SLAM as opposed to just adjust FC to target?

    So I've been using TFPC method for a couple of months now with great results. In the recent week, I've seen that although I've been maintaining FC, I'm seeing hints of algae growth. I've been able to brush the algae away and the problem seems to stay at bay for a day or two before I need to brush again. It doesn't help that the Polaris seems to get stuck on one of the steps often, so I wonder if the recent uptick in rain and plant debris are driving the recurrence of algae. CC, however, has been under 0.5ppm, which suggests otherwise.

    Is it OK for me to continue to just maintain the FC between target and minimum as I've been doing, or should I be perform a SLAM? Are there specific criteria that need to be met for a SLAM? Thanks in advance!


    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    PAGirl's Avatar
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    Re: When to SLAM as opposed to just adjust FC to target?

    Some different conditions can lead to algae growth when keeping your FC at the minimum for your CYA. Lack of circulation, your CYA might be a smidge higher than you thought, or your pump time may need to be longer. Brushing is definitely important, too. Someone with more knowledge may have additional ideas....

    They will want a full set of test results, too.
    26' X 52" Intex Ultra Frame. Intex Sand Filter
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    You can lead a horse to (clear) water, but you can't force him to swim in it!

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    Re: When to SLAM as opposed to just adjust FC to target?

    Hello Texas neighbor. Well, the sun and heat has no mercy here, so we have to be vigilant. If you (ever) suspect algae, the first thing you should do is bump-up your FC close to or at SLAM level and perform an overnight test. This will tell you for certain if you have organics thriving in the water. If it's just dust or pollen, then your filter or skimmer sock should help with that. But the OCLT is the key so that you know if you need to continue with a SLAM or not. And if you do, the quicker you nip it the better and sooner you should pass. Hope that helps.

    - - - Updated - - -

    Also, rain has little effect on an algae bloom and you can have algae with little to no CCs. So stay on it and let us know if you have any more questions. Another hot week.
    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
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    Re: When to SLAM as opposed to just adjust FC to target?

    Thanks for the reply, PAgirl. My latest results from yesterday night (Wednesday 11pm CST) are:

    pH: 7.5
    CYA: 60
    FC: 8 (was 4.5 before I added a gal of 10%LC)
    CC: 0
    TA: 60
    CH: 425

    Will test pH, FC, and CC once I get home today and post results.



    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    Re: When to SLAM as opposed to just adjust FC to target?

    Hey neighbor, thanks for that tip. Will start an OCLT at SLAM levels tonight and see what news it brings tomorrow.


    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    Re: When to SLAM as opposed to just adjust FC to target?

    Your numbers look good. If you do end-up SLAMming, just bring that pH down a hair first and you'll be ready. Have a good evening.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: When to SLAM as opposed to just adjust FC to target?

    OK, thanks for that tip. I usually adjust down to 7.2 because it tends to drift up quickly. Would that be OK or did you mean 7.4 or so? Thanks again!


    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    Texas Splash's Avatar
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    Re: When to SLAM as opposed to just adjust FC to target?

    7.2 to 7.4 is great.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: When to SLAM as opposed to just adjust FC to target?




    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    Re: When to SLAM as opposed to just adjust FC to target?

    Hi! I am a new pool owner. Had it installed the weekend after July 4th. I had the same problem, it went on for 3 weeks. I'd shock it and the water looked good for a few days. Then I'd see algae and shock again. I finally took my DE filter apart and cleaned. I ran pump for 24 hours and cleaned the filter again.
    Next year I will use the TFPC method.
    Good luck!
    Quote Originally Posted by gustafson View Post



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    Re: When to SLAM as opposed to just adjust FC to target?

    Happy to report that my SLAM was successful based on the OCLT. FC loss was only 1ppm (24 --> 23), and CC was 0.5. Interestingly, chlorine loss during the day was higher than expected, went from 20+ down to 13 in one day!

    BTW how long should one wait before measuring FC after adding chlorine to bring it to shock level? I waited about an hour but feel it wasn't long enough.


    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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    Texas Splash's Avatar
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    Re: When to SLAM as opposed to just adjust FC to target?

    Congrats on the OCLT! Your FC loss after the SLAM was probably simply because of the hot sun today. Anything above your target is not necessarily bound to the CYA and if not actively used on algae will get burnt-off. As for how long to wait after adding bleach, about 30 min should do it. An hour is plenty with the pump running.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: When to SLAM as opposed to just adjust FC to target?

    Thanks for the reassurances! Lesson learned on keeping tabs on chlorine levels and pH everyday, and CYA (and others) weekly.


    25,000 gal, in-ground, plastered gunite, Pentair NSF 60 DE Filter

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