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Thread: FC level when doing OCLT

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    FC level when doing OCLT

    I'm currently doing a SLAM.

    For the OCLT, it says that the FC level should be at least 3 ppm.

    Is there advice for whether the OCLT should be performed at shock level versus maintenance level? My intuition says that it's more likely to pass OCLT at 4 ppm (target level for my CYA) versus if I left it at 12 ppm (shock level for my CYA). But since I'm still SLAMing, I'm leaving my pool at night at higher-than-normal FC levels (and it does drop more than 1 ppm overnight).

    I've met the other two finish criteria for SLAM conclusion (low CC and clear water), and I'm eager to conclude it, but I'll keep SLAMing if that's what I'm supposed to do based on the OCLT not passing at shock levels.

    Thanks!

    Mason

    - - - Updated - - -

    Heh, I just reread the SLAM page:

    When all three are true, you are done SLAMing and can allow the FC to drift down to normal levels.

    I guess there's my answer.

    Mason
    25,000 gallon plaster pool, Pentair IntelliFlo VS+ SVRS pump, Sta-Rite System 3 Modular Media Filter Model S7M120 (cartridge), Aqua Ultraviolet UV Sterilizer (not used), Polaris 380 w/ booster pump, Taylor K-2006 test kit

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    Mod Squad pooldv's Avatar
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    Re: FC level when doing OCLT

    LOL! Do you have a question? You can do the OCLT at whatever your FC is as long as it is above 3 it doesn't really make a difference. That is why we lowered it to 3 ppm. It used to be SLAM and then it was 10 for a while. Through some more research we found no reason to raise FC just for the test. Or lower it. Just do it.
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    Re: FC level when doing OCLT

    I know OCLT can be performed anytime you want to know whether there is something "going on" in the pool that needs to be addressed. I was specifically asking about the OCLT that should be done to determine whether you're done SLAMing -- whether that should be done at the SLAM level or if it can be done at the "normal" level. Because it seems to me that a no more than 1ppm drop from 12 is a tougher test to pass than a no more than 1ppm drop from 4.

    After I made the post, I saw the line on the SLAM page that pretty much indicates that the OCLT test should be done at the SLAM level.

    Basically, I feel like my pool is in pretty good shape, but I don't want to "cheat" the test in order to declare it so. If the fact that I can't hold a SLAM level overnight means I should still continue SLAMing, then I will continue SLAMing. What do you think?

    Last night at 10:45 p.m., my FC was 15, and this morning at 6:30 a.m., it was at 9.5. That's definitely not passing the OCLT, but if I had left it at 5 last night, I could believe that it might not be lower than 4.

    Mason
    Last edited by SongMonk; 06-21-2016 at 10:17 AM. Reason: Remove extra signoff
    25,000 gallon plaster pool, Pentair IntelliFlo VS+ SVRS pump, Sta-Rite System 3 Modular Media Filter Model S7M120 (cartridge), Aqua Ultraviolet UV Sterilizer (not used), Polaris 380 w/ booster pump, Taylor K-2006 test kit

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    Re: FC level when doing OCLT

    Your thinking is somewhat off because the chlorine curve is not linear. Someone smarter than me will explain better.

    1ppm loss (or less) is 1ppm loss. Doesn't matter if your level starts at 3 or 30

    And you're right. 4.5 loss is definitely not passing. Soldier on
    15,000 gallon free form Viking fiberglass pool. Hayward Star-Clear Plus C12002 cartridge filter. Hayward Swim Pure Plus T-15 SWG. Testing with TF-100 Kit. 2 speed 1.5HP Supreme pump. Dolphin Nautilus robotic cleaner

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    Re: FC level when doing OCLT

    And you're right. 4.5 loss is definitely not passing. Soldier on
    Perfect advice. (hut, 2, 3 ,4; hut,2, 3, 4)
    Dave S.
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    Re: FC level when doing OCLT

    Thank you both.

    I believe I read that as long as the pool is less than shock level, it is swimmable. Is that true? Or should I let the levels drop down if we want to invite people over to use the pool this weekend?

    If I do that, will I be shooting myself in the foot in terms of getting the SLAM complete? I do understand that it is essential to *maintain* the elevated FC level, so the question is how much will I backtrack by not maintaining the high level. Already, I am being hurt by the fact that I can't maintain the level while I am at work through the week. I will finally have time this weekend, so I should I say no to people swimming in it so that I can really work at maintaining the high level throughout the weekend?

    Mason
    25,000 gallon plaster pool, Pentair IntelliFlo VS+ SVRS pump, Sta-Rite System 3 Modular Media Filter Model S7M120 (cartridge), Aqua Ultraviolet UV Sterilizer (not used), Polaris 380 w/ booster pump, Taylor K-2006 test kit

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    Mod Squad pooldv's Avatar
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    Re: FC level when doing OCLT

    Yes, it is safe to swim with FC between minimum and shock level. We swam every day while SLAMing last summer, FC 28 and CYA 70, wife, kids, the whole herd. Much easier and cooler to brush IN the pool! If your water is clear you should definitely do lots of swimming.

    The reason the SLAM procedure says to do OCLT at SLAM level is so you don't have to wait or actively lower FC. So, you can just do the OCLT and keep on SLAMing if needed.
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    Re: FC level when doing OCLT

    Thanks, pooldv.

    I'm committed to maintaining SLAM levels this weekend when I am home. Can I save on chlorine by letting the level fall down during the week (still keeping it above normal maintenance levels)? Or am I opening myself up to backsliding if I do that?

    I will note that CC levels are low (< 1 ppm) and the pool looked great visually before I even started SLAMing. I think my wife is wondering why I keep pouring chlorine into the pool and I have multiple dozens of empty containers in the back yard b/c recycling bin won't hold them all. I must have gone through 3 or 4 dozens jugs already since Friday.

    Mason
    25,000 gallon plaster pool, Pentair IntelliFlo VS+ SVRS pump, Sta-Rite System 3 Modular Media Filter Model S7M120 (cartridge), Aqua Ultraviolet UV Sterilizer (not used), Polaris 380 w/ booster pump, Taylor K-2006 test kit

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    Mod Squad pooldv's Avatar
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    Re: FC level when doing OCLT

    When is the last time you cleaned the filter?

    As long as FC is at target or higher you should not really lose ground.
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    Re: FC level when doing OCLT

    Quote Originally Posted by pooldv View Post
    When is the last time you cleaned the filter?

    As long as FC is at target or higher you should not really lose ground.
    I have not cleaned the filter since I inherited the pool (in February), but it is showing < 10 psi. Nevertheless, I plan on cleaning it this weekend.

    I have also never brushed the pool, b/c I don't have a pool brush! But I will get one.

    Thanks for your help.

    Mason
    25,000 gallon plaster pool, Pentair IntelliFlo VS+ SVRS pump, Sta-Rite System 3 Modular Media Filter Model S7M120 (cartridge), Aqua Ultraviolet UV Sterilizer (not used), Polaris 380 w/ booster pump, Taylor K-2006 test kit

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    Re: FC level when doing OCLT

    You're welcome. You're liable to find some funky stuff in the filter, that could be the lingering issue. Yes, get a brush, it is good for the pool to brush it once a week or two. And it helps move your SLAM along faster by exposing algae to the chlorine and killing it faster.
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