What stain is this?

[a34536]

I've noticed a few stains on the floor of the liner. I rubbed a vitamin c tablet on one of them, and pic 1 (taken under water) shows what it looked like afterwards. I had to rub quite hard for a few minutes for the stain to go. I am not sure if it was metal or not.
[attachment=1:ne55flsi]IMG_1937.jpg[/attachment:ne55flsi]

This pic shows an example of other stains dotted around the pool floor. I think they have gradually developed over the last season. I was using Trichlor until a couple of weeks ago, and suspect my pH was < 7.
[attachment=0:ne55flsi]IMG_1926.jpg[/attachment:ne55flsi]

Any suggestions on how to get rid of the stains?

current test results
FC 9.5
pH 7.6
TA 100
CC 0
CYA 80

 

[dmanb2b]

I have/had one of those from a hair pin...in my case it was an iron stain. It eventually faded over the past year.

 

[Butterfly]

Well, if the Vit C worked and you only have a small area of stains, you could crush some in a sock and hold it on the stain for a minute. Keep a close eye on it as crushed vs whole-tab may do a much faster job.

 

[a34536]

I am not sure if it was the vitamin C, or the rubbing that did it. I left the tablet on the stain for a few minutes, and didn't seem to make much difference, it was only when I scraped it with the tablet for several minutes that it seemed to disappear.

I'll try the crushed vitamin next time I'm in the pool.

Thanks!

 

[Claughaun]

I have stains like those... What are they? Did you get rid of your's?

 

[a34536]

No, not yet. I tried placing a tablet on a stain and leaving it, but the stain didn't go. I did use copper based algaecide when closing the pool last winter (before I discovered TFP) so wonder if it is from that.

Not sure what to try next. I haven't tried the crushed vit C tablets yet though.