Passing OCLT but yellow (algae?) on walls.

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undrwater

undrwater

0
Sep 20, 2018
61
Cerritos, California (SoCal)
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Ell
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Build Type: Plaster
Volume: 16000 gallons
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Latest Test Result Summary:
FC: 7.0 (an hour ago)
CC: 0.0 (3 months ago)
pH: 7.5 (an hour ago)
TA: 80 (yesterday)
CH: 440 (6 months ago)
CYA: 45 (9 days ago)
SALT: 2400 (one month ago)
TEMPERATURE: 75° (one year ago)
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Test Results 10-08-2019 @ 10:46 AM
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Free Chlorine: 7.0
pH: 7.5

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Test Results 10-06-2019 @ 08:26 PM
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Free Chlorine: 6.0
pH: 7.6
Total Alkalinity: 80

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Test Results 10-03-2019 @ 08:45 AM
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Total Alkalinity: 70

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Test Results 10-03-2019 @ 08:44 AM
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pH: 7.4

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Test Results 10-03-2019 @ 08:43 AM
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Free Chlorine: 10.0

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Test Results 10-02-2019 @ 05:25 PM
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Free Chlorine: 4.5
pH: 7.8

As per title. Summer is ending here in socal, and I've been fighting the yellow stuff for a couple of weeks. Water looks awesome, and I'm passing OCLT.

I may be in denial, because I keep thinking it's pollen. I'm pretty sure I need to SLAM, but if I'm already passing OCLT and the water looks good, do I stop when the yellow disappears?
 
Visible algae is a reason to SLAM your pool. Some algae can develop a biofilm that protects it from the chlorine, thus the recommendation that during a SLAM you brush your pool each day.

There is a good possibility that if you took your start reading for the OCLT then brushed the pool in the areas you see the algae it would break up the biofilm and allow the chlorine to get to the algae. I'm guessing you would fail that OCLT.

Pollen doesn't generally stick to walls, but falls to the floor of the pool.

If you are seeing this on the shady side of the pool I will further guess you are seeing mustard algae.
 
Something to add:
I have a second pump that currently isn't connected to anything above ground. I'd bet that the pipes coming from that pump into the pool are ripe for algae growth. The outlet to the pool for that pump is on the deep end of the pool. I'm not going to use that pump for anything in the foreseeable future, so I'd prefer to block it off. Should I do that at the pool side, and would a freezer plug be the best thing to do that with?

Thanks!
 
It would be good to plug off at the pool shell. I assume you mean a rubber expandable plug. Check the outlet to see if it is threaded. You might find a threaded cap that will fit.
 
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I just skimmed this thread but I am not sure you have algae. If you water is crystal clear, passing the OCLT is a pretty good sign for no algae.

Are you brushing the pool walls, running the filter 254/7 and then still passing OCLT?? If so, that's likely not algae.

Pollen in October is sketchy, too so I think I would do this.

1. Run the pump 24/7
2. Brush the pool walls and floor once daily
3. Elevate your FC to about 10 and hold it at 10 for at leqast 24 hours.
4. At the end of all this brushing and filtration and high chlorine, now run another OCLT and report the results.
 

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Thanks @duraleigh. I already started SLAM, and running the filter non stop. There was a period a week and a half ago where I could not get the time to brush, so whatever it is, accumulated.

I'll keep my FC elevated for the next couple of days, and continue brushing (I'm at it about 3 times a day now). Friday night I'll start OCLT and see where I am Saturday. For what it's worth, there's less yellow, but that could easily be due to the increased brushing and running of the pump.
 
Last night at 7:32 my FC was 19, this morning at 10:37 it was still 19. CC is .5. These are SLAM levels, but not MA levels recommended by @mknauss.

I'm beginning to suspect that perhaps this isn't mustard algae after all. After brushing and maintaining FC, there is still sign of yellow along the wall and at the base of the walls. Some sign on the floor. There's nothing in the hot tub, which seems strange.

I purchased a cap and closed off that pump port that was going to nowhere.

Someone in a different thread mentioned ragweed pollen that is showing in some areas. This is a possibility, though I haven't seen pollen sign anywhere above the pool, as might be expected. We are having "santa ana" wind conditions and fires in my area, so that is adding some dust and ash to the pool.

I think my plan is to allow the pool to drop to 10 ppm FC, and maintain it there for a while. Otherwise I could bump it up to MA levels.
 
duraleigh said:
It's not clear to me if the brushing is helping......is it?
Click to expand...
It's not quite clear to me either. Initially when I brush, it seems as if it removes the yellow, but when I return to the pool after a bit (even just a few hours) I can see some yellow again.

Perhaps @JamesW is correct? I added salt at the beginning of summer for feel; can that contribute to iron stains? As for testing with vitamin C, I only have that in the form of limes right now. How does one usually perform that test. I'll go check at pool school to see if it's there.

I'll also get some pics in a sec.
 
You need to determine (or help us understand) if you have stains that won't brush of or if you have debris that brushes away and then reforms. Both are fixable but your descriptions are not clear enough to understand what is going on. A good picture is worth a thousand words.
 
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Probably iron and copper. Ascorbic acid might help but it can make things worse. So, it's a risk.

Sulfamic acid might work but the metals would be in the water and would eventually redeposit.

If you can get the stains to come off, you would probably be better off draining and refilling to get rid of the metals.

However, draining can sometimes cause the pool to pop out of the ground and ruin the pool if the ground water is high.

Do not drain without consulting a local expert for their advice about draining and refilling.
 
It's still a guess but that pool surface has been neglected for a LONG time and looks like a combination of iron, maybe copper and probably calcium scale with embedded algae thrown in for good measure.

If it was my pool, I would check with a local pool guy to find out about the water table (so the pool won't float) and then I would completely drain and have a professional come in and acid wash the whole thing.

Acid washing takes away SOME of the longevity of the plaster but I don't see a decent alternative.

The pics really help, btw.
 

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