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Thread: Greenish brown crud in pool defies treatment efforts

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    Greenish brown crud in pool defies treatment efforts

    A few weeks ago, my pool started collecting greenish powder on the bottom.

    It did NOT climb up on the sides.

    It felt neither spongy nor slimy, I couldn't feel anything at all when I tried to rub it between my fingers.

    My pool is covered under a screen (don't know whether that's supposed to help keep pollen out).

    It started right after I slacked for a day and didn't measure my chlorine level right when most of the trichlor tablets I was using to raise my CYA dissolved. The FC reading was definitely too low that one day--bad, but not zero: I think maybe 0.5 or 1.0?

    SLAMed the pool and the next morning it met all three criteria for doneness.

    Later the same week the wicked stuff started coming back. The lowest my FC was at any point after I SLAMmed the first time was 3.5. Thinking it was probably pollen, I put on a skimmer sock, ran the pump a lot more, and vacuumed and brushed frequently.

    None of this helped much.

    I put some of the greenish stuff in a mason jar with pool water and left it outside. Someone suggested this in another thread a few years back to test for algae vs. pollen. The jar remained clear.

    Eventually, the water started to get cloudy, to the point where I could not even see the drain on the bottom very well. So last weekend I started SLAMming the pool once again. Once again, it quickly passed the the CC and OLCT criteria of the three pronged test, but the water was not clear, so I continued to SLAM.

    Since I worked long hours and the filter is a hassle, and pressure gauge was reading at clean levels, I never cleaned the filter until Wednesday. When I did, it was REALLY green. Within a day or so after I cleaned it, the pool water once again became crystal clear and sparkly, but by this time the CC had drifted up, and now the completion test fails based on the CC reading. CC is currently 1.5, yet the OCLT test passes with flying colors!

    What's more, although the water itself is still beautifully clear (at least so far), the crud on the bottom that started this whole thing in the first place has returned!

    The start of SLAM test kit results are as follows:

    FC 3.5
    CC 0.5
    pH 7.3
    CH 200
    TA 130
    CYA 30

    I am stumped as to what is going on. If I were just too impatient, I would guess that the CC value would stall for awhile instead of actually increasing while I was still SLAMming, wouldn't it? What IS the crud on the bottom? It can range from greenish to brownish. Could it be organic matter that continues to enter the pool impacting chlorine demand reflected in the elevated CC reading? If so, will I ever be able to stop SLAMming? The chlorine cost is no problem, but I cringe to think of my electric bill after running the pump 24/7 for a few weeks. Or is there a hidden source causing the high CC readings? If it's useful information, my CC measurement has NEVER been 0. It's always 0.5 when things are OK.

    Any insights as to what could be causing my problems and how to fix things?
    5k gal, IG vinyl, Sta-Rite P2R (or P2RA?) series pump, 100 sq ft cartage filter, install date 1996

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    Mod Squad zea3's Avatar
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    Re: Greenish brown crud in pool defies treatment efforts

    It is probably algae. Are there any ladders or light niches where algae could hide? CC tends to climb as you slam, that's normal. Once all the algae is killed off as you continue to slam the CC will burn off. Raise the FC to slam level and keep it there until you have met all 3 criteria for 2 days in a row.
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    Re: Greenish brown crud in pool defies treatment efforts

    If your CCi still high you need to take FC back up to SLAM and keep it there through the day too if possible until CC drops. As for the stuff in the bottom, will it disperse if you brush it? If so then I would say dirt and pollen that has got through the screen. Vacuum it up and keep your filter running.
    Lisa
    Intex AG vinyl 15' x 48" 4,300 gallons due to skimmer install, Krystal Clear SF pump combo 2800 GPH, Krystal Clear SWG, Pool Blaster Max vacuum, Hayward thru the wall skimmer, TF 100 test kit with speed stir, K 1766 Taylor salt test, My SLAM Process

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    Re: Greenish brown crud in pool defies treatment efforts

    Re: stuff on bottom: Yes, the stuff on the bottom disperses readily when brushed.

    Re: Probably algae: If it is algae, could it be mustard algae, given all the time it's taking to resolve something that seemed relatively minor? It's been in my mind, but there are definitely some differences in what I'm seeing and what's described in the mustard algae article.

    SLAMming continues...
    5k gal, IG vinyl, Sta-Rite P2R (or P2RA?) series pump, 100 sq ft cartage filter, install date 1996

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    Re: Greenish brown crud in pool defies treatment efforts

    Good call. Continue slamming.
    Lisa
    Intex AG vinyl 15' x 48" 4,300 gallons due to skimmer install, Krystal Clear SF pump combo 2800 GPH, Krystal Clear SWG, Pool Blaster Max vacuum, Hayward thru the wall skimmer, TF 100 test kit with speed stir, K 1766 Taylor salt test, My SLAM Process

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    Re: Greenish brown crud in pool defies treatment efforts

    During your SLAM, how often are you checking FC? What is the FC target level you are trying to maintain?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Greenish brown crud in pool defies treatment efforts

    Quote Originally Posted by duraleigh View Post
    During your SLAM, how often are you checking FC? What is the FC target level you are trying to maintain?
    Each day I measured at dawn and dusk, and most, but not all days, I arranged for my wife to measure over lunch.

    My pre-SLAM CYA figure was after I had been raising the level with trichlor tablets, and I didn't know if I might have a false low reading for a week, like you get by adding stabilizer in a sock like most people do, but I felt pretty good about how good the value would be and it closely matched my calculations. Nevertheless, just to be safe, I have been targeting an FC level of 13.5 instead of the 12 listed on the chart, just in case I flubbed the CYA value.

    I remeasured today under textbook perfect lighting conditions, and am now confident of the 30 PPM CYA figure, so I can go forward targeting 12 PPM FC, unless I have a good reason to do otherwise.

    With one exception a few days ago the FC level has never been too much below 12 when I added chlorine (it was 7 that one evening: I may have started closer to 12 and had a sunny day where my wife didn't check over lunch).

    BTW: I tested a few minutes ago, and it now looks like my CC is finally starting to drop! I would say it is 1, or maybe even a little less, now, although part of my problem is that I am not too confident of the accuracy of my sub-1 PPM measurements, since the TF-100 test kit has a resolution of 0.5 PPM per drop, and sometimes it's hard to discriminate between a slight tinge of pink and none at all (twice, when determining CC!).
    5k gal, IG vinyl, Sta-Rite P2R (or P2RA?) series pump, 100 sq ft cartage filter, install date 1996

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    Re: Greenish brown crud in pool defies treatment efforts

    Just by way follow up, my CC measurements went back up, then eventually hit a real rising trend a couple of weeks after that last post. (I was what? At least three full weeks of slamming by then?) Then I finally found this other thread, starting here.

    Well I had been using this same vial for the Chlorine drop test since I started and it was starting to darken. Then toward the end I got so frustrated with my problem, that I started leaving the previous night's test water/chemicals in the vial without rinsing until the next morning. When I cleaned it my problem improved substantially and when I used a different vial it went away altogether. Even now, I seem to be getting CC readings of 1.0 in the "cleaned up" vial, but I'm reliably getting passing readings every time in the new vial, and my pool has been sparkly for several weeks now, including the entire week since I stopped slamming. It appears to me that was the issue.

    I haven't seen my electric bill yet. I feel like such an idiot. I thought my days of such expensive mistakes were over when I had figured out not to get "pool stored" last fall.
    5k gal, IG vinyl, Sta-Rite P2R (or P2RA?) series pump, 100 sq ft cartage filter, install date 1996

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    Mod Squad pooldv's Avatar
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    Re: Greenish brown crud in pool defies treatment efforts

    Congrats on a sparkly clean pool! And being finished with your slam!
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