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Thread: FC diving during the day after SLAM

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    FC diving during the day after SLAM

    Hi all - I've been lurking in the shadows, consuming the wealth of information on here and I have something that I can't seem to find a similar situation of and decided to post.

    First off, as some background - I've been using the evil chlorine tabs, powdered shock and a multitude of different algaecide since purchasing our house about four years ago (with pool - my first pool). I decided to make the move to a SWG about a month or so ago and have been trying to get the pool to a solid base level before making the switch. In the process, I found that my CYA levels were somewhere between 100 and 200.

    I've also been trying to get the pool warm enough for some upcoming swimming lessons for the kid, so I've had a solar blanket on it. When I took the blanket off to start draining the pool to address the CYA levels, I had a mess of yellow algae to deal with as well....Sooooo to the point - after draining/refilling (getting the CYA to 40-45 per my testing), I started a slam with liquid chlorine and tried to keep the FC between 16-20. There were some swings during the days where it got below that level (low to mid teens), but it wouldn't have been there for very long. I assumed this was part of the SLAM process with the chlorine eating all of the nastiness. After two days, I had no overnight loss of FC, the water was clear and no CCs in the morning of the clean OVCLT. I started the day on Sunday with a FC reading of 14 and assumed it would slowly regulate from there. Mid-day on Sunday, the FC dropped to 10 and then by the time the sun went below the trees, it was all the way down to 5.

    Is that a normal amount of FC loss during the day? I'm not getting any loss at night, so I think the pool is ok, but it seems like the sun is destroying my chlorine. I verified the CYA readings a couple of times (again somewhere in the 40-45 range each time) and I didn't have and CCs coming back to indicate that the FC was actually working that hard. I'm still just using liquid chlorine (the stuff made for pools, purchased at the home improvement store). I should mention that my pool is completely exposed, no screen, and no shade for the majority of the day and I'm in Florida...so the sun was pretty intense this weekend.

    Having just wasted a s-ton of water with the pool draining, I'm terrified to start jacking the CYA back up, but is that what I'm missing here?

    If it helps, here are the numbers from this morning:

    FC - 4.5 (brought up to 9 after taking these readings)
    CC - 0
    pH - 7.5
    TA - 120
    CH - 350-375
    CYA - 40-45
    In ground plaster pool - ~20k gallons | Hayward Regenex 700 DE Bump Filter | Hayward Max-Flo VS pump | Hayward AquaRite Pro 40K Salt Cell (w/ S&D)

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    Jezza's Avatar
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    Re: FC diving during the day after SLAM

    If you had mustard/yellow algae then there is a process of elevating your FC further towards the end of your SLAM for 24 hours. Here is the article with instructions.
    11 000 gallons, IG, Fibreglass, Monarch Sand Filter, Davey Typhoon C100M 1HP pump, Davey Chloromatic Mc16CTO ESR SWG, Davey Pool Wall Climba Robot, Daisy Solar Cover,
    K-2006

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    Mod Squad zea3's Avatar
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    Re: FC diving during the day after SLAM

    Hi, welcome to TFP! What kit are you using to test with? How are you reading the CYA test?
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    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
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    Re: FC diving during the day after SLAM

    Jezza - Ugggghhhh, that mustard add-on does not sounds conducive to sanity or maintaining full time employment. That aside though - would that explain the drastic FC drop? I would think that if the chemicals were still eating significant enough amounts of algae to account for the loss that I would be getting some CCs, which I haven't for a few days now.

    zea - I'm using the TF-100 kit. I did just read some additional information in some other posts about the whole "full sun, back to the sun" part of the technique that I was previously unaware of. I definitely had full sun, but the tube was more than likely in it. I was also staring directly into the eyes of that black dot like it was Medusa mercifully ending my pool sorrows. Evidently that's problematic too. I'll run another CYA test in the morning with some shade and avoiding eye contact.

    Much appreciated on the quick responses!


    Edit - Just checked the FC after getting home from work. It was 9 at 11:30 AM today. 5 after dark....thought I'd keep you up to date on the numbers I'm seeing.
    In ground plaster pool - ~20k gallons | Hayward Regenex 700 DE Bump Filter | Hayward Max-Flo VS pump | Hayward AquaRite Pro 40K Salt Cell (w/ S&D)

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    Re: FC diving during the day after SLAM

    The CC's are only one measure. You can still have algae but have a lowish reading for CC especially as the sun can burn them off fairly quickly.

    Your FC drop does seem a little high. I would perform another OCLT as that will give you the strongest indication as to where things are at. Obviously failing that, you would have to resume the SLAM.

    The CYA test needs to be done in full sunlight with your back to the sun-not the shade for an accurate reading. It helps to glance for the dot, look away, glance again rather than staring at it. You can also repeat the test as many times as you like by pouring the solution back into the mixing bottle and repeating. You can then average out the readings which can help with the consistency of your readings. Hope that helps!

    How is the water looking- is it relatively clear?
    11 000 gallons, IG, Fibreglass, Monarch Sand Filter, Davey Typhoon C100M 1HP pump, Davey Chloromatic Mc16CTO ESR SWG, Davey Pool Wall Climba Robot, Daisy Solar Cover,
    K-2006

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    Re: FC diving during the day after SLAM

    Ok, new day and...no FC drop last night - 25 (ran out of chlorine trying to get to my mustard super shock of 27) at 11:00. 25 again this morning at 7:00. No CCs at either test.

    I just did another CYA test and ended up with slightly higher readings with the back-to-the-sun and glancing look technique. On two subsequent readings, I was just above and just below 50. Nothing drastically different from previous readings though. If anything, that would seem to make my FC loss even more confusing.

    Jezza - the water is crystal clear. I can see the texture of the plaster and specs of dirt in the 8 ft. deep end.

    I just pumped some more chlorine in to get to the mustard super shock level. I'm going to try to maintain that for the next 24 hours and then see what happens with the chlorine tomorrow. I'm still confused by the large FC drop with no CCs though. It just doesn't make sense to me, but chemistry wasn't my strong suit.
    In ground plaster pool - ~20k gallons | Hayward Regenex 700 DE Bump Filter | Hayward Max-Flo VS pump | Hayward AquaRite Pro 40K Salt Cell (w/ S&D)

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    Re: FC diving during the day after SLAM

    I'm in the same boat. Two nights ago had no FC loss and very little throughout the day. Then boom - loss that night and following day. I'm at two weeks now in my SLAM. Feels like zero progress and lots of $ spent on chlorine. Not to mention the countless hrs and feels like I'm losing my friggin mind! Last night I went into the pool for the third time with my dive gear. Used my dive light last night to clean underneath my ladder steps with a toothbrush. Didn't see much however when I pulled the rubber feet off the stainless ladder legs I found algae hiding inside the hollow legs. Hoping this is the last vestige. At any rate, check every nook and cranny you can find. I'm seriously ready to check myself into a psych ward I'd this doesn't work.

    30k gal, IG, vinyl, Pentair Tagelus TA 60D sand

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    Re: FC diving during the day after SLAM

    Sounds like a plan- aralph makes a good point. Have you checked and scrubbed in classic algae hiding places- behind light niches, ladders, inside and around return jets and skimmer boxes etc?
    11 000 gallons, IG, Fibreglass, Monarch Sand Filter, Davey Typhoon C100M 1HP pump, Davey Chloromatic Mc16CTO ESR SWG, Davey Pool Wall Climba Robot, Daisy Solar Cover,
    K-2006

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    Re: FC diving during the day after SLAM

    Sure wish I could say the ladder was it...Still battling.

    30k gal, IG, vinyl, Pentair Tagelus TA 60D sand

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    Re: FC diving during the day after SLAM

    I found a forest of gunk under the steps on my ladder yesterday. I removed them (to be replaced, not cleaned), and in the process knocked a bunch of algae into the pool. I maintained the mustard shock level yesterday and vacuumed the loose stuff out. Last night I had around 1 CCs and had an overnight loss of about 4 ppm. I'm not sure if the change in the overnight test and the appearance CCs is due to disturbing the kelp forest or running at a higher chlorine level, but I'm going to try to maintain the higher chlorine level for a few days and see how that goes.

    As for the other places - I removed the ladder pads as well. They had a little bit of algae in them. I would assume the inside of the ladder arms have something in them, but there's no way for me to get in there. Not sure what I could do about that. The light socket, jets and skimmer are all clean. The only other offending culprit would be inside the drain cover. I don't have the ability to get to that though, so again, not sure what to do about it.

    Hopefully the nuclear chlorine levels will handle everything over the next couple of days.
    In ground plaster pool - ~20k gallons | Hayward Regenex 700 DE Bump Filter | Hayward Max-Flo VS pump | Hayward AquaRite Pro 40K Salt Cell (w/ S&D)

  11. Back To Top    #11

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    Re: FC diving during the day after SLAM

    I was able to get inside my ladder arms with my fingers and with a toothbrush. Took my drain cover off but it was squeaky clean inside, same as my return. Haven't seen anything in/around jets.

    30k gal, IG, vinyl, Pentair Tagelus TA 60D sand

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