I have some brown stains on my pool steps and some similar, but lighter patches on the vinyl liner. Thought it might be metal staining? (maybe from the copper and titanium plates in the Ecosmarte - hopefully getting that out by end of this week). Same thing happened last year - pool store recommended Sparkle Stain Off Stain Remover and it worked, but I had to repeat every couple of weeks. I don't know what the active ingredient is. Anyone familiar with this product?
It says it doesn't affect pool chemistry, but I have no idea what it is, so I'm skeptical.