black stain line around steps

This is year two for our IG vinyl pool (STILL building it ourselves -- working on the fence and deck pavers now). This site has been a life saver! Literally -- I think I'd have had a nervous breakdown if not for the calm wisdom here.

We have black line about an inch and a half wide all around our white steps and swim outs where the water levels were (one line for where it was last summer and another where the water was this past winter.

We use water-softened well water to fill, don't think we have any problem with metals, and have a SWG that we haven't started up yet.

Any suggestions for cleaners? Should I start with Aspirin (thanks for the link in the other thread) or something else. Tried Baking soda -- didn't do a thing. Thanks. Joie :)

Try a magic eraser, it takes the water mark off my fiberglass pool very easily. You can also try a baking soda paste, or a vinyl cleaner using a mesh scrubbie.

Sounds like the same black stain I have around my Above Ground pool. I've tried many different things. The surface dirt will come off but the stain will not. We're replacing our liner this year mainly because of that ugly stain. I would like to know what caused the stain so I won't make the same mistake with this new liner.

We also partially filled the pool with spring water.

What's odd is that we don't have the black stain on our liner, only on the fiberglass steps and swim-outs. I'm guessing the magic eraser didn't work with your stain? Joie

I've found that Dow Bathroom Cleaner ("scrubbing bubbles") works good on cleaning the steps. I get the black stain every year and struggled with it before trying it out of desperation. Hope it works for you, we're very satisfied with the results.
Tony