Our liner has been through 7 seasons, and 6 of them have been BBB. We just closed the pool, and although there has always been some liner fading each year below the water line, it's much worse than usual this year. It starts at the water line and seems to go down the side, but doesn't affect the bottom much. It's much worse on the "sunny side" of the pool, but the "shady" side is also affected. I'm trying to figure out the cause, so we don't make it worse. Two things come to mind:
1) We have never covered the pool in the winter. So, the sun beats on it all year long -- and actually, we do get lots of winter sun in Wisconsin. Possibly making matters worse, it fills with snow and the sun bounces off the snow. Would it help to cover it? There is a black vinyl cover, but I dread getting the water and snow off of it all winter long. We've had no problem opening the pool in the spring, so if there's not a compelling reason to cover it, I'd rather not. We've thought about purchasing a leaf net cover, but I'm not sure that would help the fading issue.
2) I had a heckuva time getting my CYA to the proper level this year. I kept adding it, and even though I was adding the proper amount for my pool size, I kept having to go buy more; then I'd test, and again it would need more. And once I got the CYA to the right level, a week later, it was too low again! (It's always been this way, but was really bad this summer.) As a consequence, we did have to use more bleach than usual. (No, I don't backwash excessively.) Could this have been the problem?
In all other aspects, the liner seems to be fine. It just doesn't look too good, especially when it's drained!