Brown Stain

We have a 16x40 fiberglass pool had it covered for the winter when we opened it color was green it is 5 years old we cleaned it cleared the water but have a brown stain on steps, sides and some on bottom have tried everything, lemon, magic erase, stain remover etc. We have had it tested for iron, copper everything we can think of and it shows nothing does anyone know how we can get it out. The only thing we haven't tried is to drain it and wash but I read not to acid was a fiberglass pool. Help!

If you use a wet rag to hold some iron out against the stain for a few minutes . . . and it's not removed or lightened, it's almost certainly not iron.

If you do the same, but using dichlor or cal hypo . . . and it's not removed or lightened, it's almost certainly not tannins from leaves, etc.

Those are the only two brown stains I know about. I have seen some brown mystery stains . . . but I never figured out what they were, only what they weren't.

Good luck,

Ben

PS. Do NOT let any of those three chemicals -- Iron Out, cal hypo, or dichlor -- come into direct contact with each other. If you do, bad things WILL happen.