Deep End Yellow Stain Help

[fredder9]

Hi.
Been a few years since I've been on the forum.
Plaster pool, surface new 3 years ago.
Surface seems a bit more susceptible to staining than previous surface for sone reason (acorns, other cause yellow spots that persist). But, opening pool this year had this staining on deep end. I expected it to recede over time, has not. Not organic, won't brush off with metal bristle brush. Pool guys will tell me to acid wash which I am loathe to do. Read about metals in water, Vitamin tablets, etc. I'm sure obe of you folks know exactly what to do. Please help, thanks in advance.

25,000 gallons.
18x39
Deep end 7'
Cya=30
Alkalinity=110
CH=280
Ph=7.6
TFT-100 test kit

 

[ajw22]

Are the stains rough to the touch?

 

[mknauss]

How do you chlorinate?

 

[poollifeguard]

Could be metal stains, especially if you've got well water. I'm not an expert, but maybe try testing for metals? There are kits available at pool stores.

 

[fredder9]

Are the stains rough to the touch?

How do you chlorinate?

Only liquid chlorine. Follow SLAM each year, not as disciplined as I used to be. Doesn't brush off.

 

[fredder9]

Are the stains rough to the touch?

How do you chlorinate?

Only liquid chlorine. Follow SLAM each year, not as disciplined as I used to be. Doesn't brush off.

Are the stains rough to the touch?

Just dove in and gave the area a feel. Not rough, same feel as surrounding non-stained area. But interesting as I have one that was like a bluish / purple "substance" that ran down a side wall from one of the jets and when I brushed it in May it turned yellow but I couldn't brush off the yellow. Well...just now gave that a feel and the area immediately surrounding the jet was rough. Metal brushing smoothed it and removed stain, but the 6" or so streak coming from it is on smooth surface won't brush off. Have a few spots spots about 1/4" diameter that look like from something dropping in pool (picture attached). These just hang around without fading and can't brush them either.

 

[fredder9]

Could be metal stains, especially if you've got well water. I'm not an expert, but maybe try testing for metals? There are kits available at pool stores.

I've considered that but haven't acted to get tested...will do.

 

[mknauss]

If it does not brush off it is not likely algae.
Use a handful of vitamin c tablets in a thin sock. Crush them a bit and set on the stain.

 

[fredder9]

If it does not brush off it is not likely algae.
Use a handful of vitamin c tablets in a thin sock. Crush them a bit and set on the stain.

Read that, but didn't want to try unless I knew wouldn't damage surface. Also figured it was too big of a stain to attack this way. But I guess it's informative if it clears the immediate area. Just use drug store vitamin C pills?

I mentioned in a reply to someone else that last year I had a similar, though much smaller, stain at this time. I set a 3" chlorine puck on it and a day or too later had a 3" white circle so it removed stain but I was worried it would damage surface. It eventually faded. Never had these issues with previous marcite finish I had 20 years maybe coincidental though.

Thank you for response.

 

[mknauss]

Only set the vitamin C on the spot for a few minutes. If it is iron, it will clear instantly. Yes, plain vitamin C.
When trying the puck, no more than 5 minutes on the spot.
See Stains in Your Pool

 

[fredder9]

Only set the vitamin C on the spot for a few minutes. If it is iron, it will clear instantly. Yes, plain vitamin C.
When trying the puck, no more than 5 minutes on the spot.
See Stains in Your Pool

Got it, thank you. Will give it a shot this week.

 

[fredder9]

Only set the vitamin C on the spot for a few minutes. If it is iron, it will clear instantly. Yes, plain vitamin C.
When trying the puck, no more than 5 minutes on the spot.
See Stains in Your Pool

Hi.
Report up stain hasn't changed.
The latest:
Water check at pool store (which I haven't been to in 3+ years) using BioGuard computer check said pH=8.1; TA=127; CH=182; CYA=31; Saturation Index=High. No metals.
My own TFT-100 prior to pool store said pH=8ish; TA=140; CH=240; CYA=30. Using drinking water test strip also no metals.
I figured I needed to get pH / TA adjusted since Saturation Index High. Added 1/2 the recommended dose. My own check now says pH=7.8ish but TA still 140. I'll add the rest tomorrow.
I chose to raise CH 50ppm as it would be better by my measure or theirs, I'll recheck tomorrow.
I kept not getting to store to get Vitamin C so did the non-recommended put 3" chlorine puck on portion of the spot. Removed after 2 hours. Didn't completely remove stain but can see a 3" circle changed in color from surrounding area. I don't know if that means it's organic...but I know it's something I did last year on the much smaller stain I had at that time fast forward to this year was 100% gone when I opened this year - maybe because if the pool being bombed with chlorine when I closed it. That's where I'm at until I do the Vitamin C check.
I did keep FC > 15ppm sunce our last communication and ran filter 24 hours. No effect. Still keeping FC at shock but filtration back down to 12 hours.
Anyway...thought I'd focus on getting chemistry perfect then get back to the stain. If any info here gives you a specific thought to share thank you in advance.