Diagnosis?

GoBlue01

Member
Oct 11, 2021
5
Brookeville, MD
Pool Size
3000
Surface
Vinyl
Chlorine
Liquid Chlorine
A couple months ago, we installed an outdoor elite endless pool, vinyl liner. We have an automatic retractable cover, so pool is always covered except when in use.

Developed patches of a fine particulate-like substance on the walls and bottom. Brushes off very easily but it’s incredibly fine - passes right through a coffee filter, for example. See attached photos, taken at night with lights on.

I started a SLAM yesterday after finding this site, but I noticed this morning that the pleated cartridge filter had a greenish/yellow hue before hosing it off, making me wonder if I could be dealing with mustard algae?

(FC went from 13 to 10 over 12 hrs overnight. CC is <= 0.5. CYA 34. Using liquid Cl 12.5% with target 14 during SLAM.)
 

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Oly

Gold Supporter
Jun 28, 2017
2,323
Fresno, CA
Pool Size
27000
A 2ppm FC loss overnight points to organic contaminants. How are you testing your water chemistry? A CYA of 34ppm is suspect. If we assume your testing procedures are correct then you are doing the right thing raising your FC. Let's confirm you are on track with your target levels.
 

GoBlue01

Member
Oct 11, 2021
5
Brookeville, MD
Pool Size
3000
Surface
Vinyl
Chlorine
Liquid Chlorine
I’m testing FC with the FAS-DPD method from the K-2006 kit, using 10mL volume at these FC levels.

CYA was tested at a local pool store yesterday using some sort of auto-analyzer that they have. (When I was using dichlor for a short period of time, I would measure FC before and a couple hours after each addition and record 0.9x of the amount as CYA. Kept a running total and stopped at 40ppm, shifting over to liquid chlorine entirely, so with some modest splash out, their 34ppm seemed believable to me.)
 

Oly

Gold Supporter
Jun 28, 2017
2,323
Fresno, CA
Pool Size
27000
Thanks, your calculated CYA ppm is reasonable. Have you cross checked your calculated level with the CYA test in in your K-2006 to be sure? If your CYA is actually closer to 40ppm your SLAM target would be 16ppm FC. Let us see your recent test results for pH, TA and CH. Keep your SLAM in progress and check your Overnight Chlorine Loss Test again after several days. Cleaning your filter regularly during this process is smart. Any chance swimmers using your pool are getting in after applying skin care lotions or sunscreen?
 

GoBlue01

Member
Oct 11, 2021
5
Brookeville, MD
Pool Size
3000
Surface
Vinyl
Chlorine
Liquid Chlorine
Thanks, your calculated CYA ppm is reasonable. Have you cross checked your calculated level with the CYA test in in your K-2006 to be sure? If your CYA is actually closer to 40ppm your SLAM target would be 16ppm FC. Let us see your recent test results for pH, TA and CH. Keep your SLAM in progress and check your Overnight Chlorine Loss Test again after several days. Cleaning your filter regularly during this process is smart. Any chance swimmers using your pool are getting in after applying skin care lotions or sunscreen?
I can repeat CYA with the K-2006, but when I’ve done it before it was below 35, which is the minimum detected by that kit. I haven’t added any stabilized chlorine since then.

Just posted TA 90 (and has been quite stable) and CH 140. I thought pH test was not accurate at these FC levels, so haven’t rechecked since I dropped to 7.2 for SLAM, but could do it if recommended.

no sunscreen or lotions.

obviously my question is whether or not this could be mustard algae given it would affect the last 24 hrs of SLAM.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
2,999
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
IF it is mustard algae you complete the slam process first- passing all 3 end of slam criteria (this includes the water being crystal clear with no recurrence of algae dead or alive)
THEN - raise to MA level for your cya for 24hrs and follow the rest of the MA protocols (putting all pool stuff in the water etc.)
while currently slamming you may want to clean your cover with a diluted bleach solution.
They have been known to harbor algae.
Also check/clean all nooks & crannies like light niches, drain covers, ladder handrails, water features etc.
The inquiry about the ta & ch was to rule out the possibility of scale as the stuff in the video looked quite white & flaky but those numbers don’t seem suspect & are in line with Recommended Levels.
Slam on 😎
 

GoBlue01

Member
Oct 11, 2021
5
Brookeville, MD
Pool Size
3000
Surface
Vinyl
Chlorine
Liquid Chlorine
Appreciate it. Seems there’s no definitive test for mustard algae. It’s more offwhite than yellow, but the filter is collecting very light green (yellow-green?) crud daily, albeit not too much after night 2. It’s very fine, billowed off when brushed, and was patchy on sides and bottom. No pollen around, and pool mostly covered anyway. Definitely not gritty.

So maybe fits? I don’t see much harm in ramping up to MA levels for the last day other than potential bleaching to a royal blue vinyl liner…..if that’s even a concern?

FWIW, second night went from 14 to 11.5. We’ll see what happens tonight. Continuing to brush all reachable surfaces daily…
 
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Mdragger88

Bronze Supporter
Jun 1, 2018
2,999
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
The only way to know is if it returns after slam at normal but acceptable fc levels. Regular algae can also be different colors other than green.
MA likes shady areas & tends to grow on walls so doing the mustard algae protocol after the slam process is probably good insurance in your case.
Here’s the write up for easy access 👇
Btw - try to leave the cover off for a while when u can - this allows the cc’s produced during slam to escape.
 

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