Hi, we have a pretty old vinyl liner pool, ~ 27,000 gallons. We use Bromine tablets in a cylinder-type dispenser near the pump. During the last few years, I've noticed that the inside of the white plastic skimmer has begun to develop a pretty ugly black stain which seems to have formed at the waterline. Now I've read quite a few posts here talking about black stains inside the skimmer, but they all talk about "scum" and are described as being gooey or sticky or gummy, and having to do with oils in the water.
But our staining isn't like this - it's quite "dry" in the sense that it seems to be embedded into the plastic itself. If you run a finger (um, I guess not just any finger; specifically one of your own ) over the stain you don't feel any gumminess or stickiness. In fact you cannot feel it at all.
I'm guessing that since our staining is different from the descriptions of black staining that I've read about here, it may have some other cause, and wondering how it might be remedied. IMO it makes the inside of the skimmer look pretty disgusting.
If it's of any relevance, the few inches of our liner that is always above the waterline also have a darkness/blackness coloration. I tried using a magic eraser to lighten that up to match the color of the liner that's always underwater, but using that seemed to be rubbing the design out of the vinyl, which looked even worse.
Thanks for any suggestions!