Scum line below waterlevel, won't scrub off

First post but here goes.

Water test results:

Cl - 5+ probably closer to 8-9 as I just shocked
PH - 7.2
TA - 110
TH - 280
CYA - 30 but probably a little less

I opened a 24' above ground after purchasing this house 1 year ago. Pool has not been opened in 2 years and the cover caved in over the winter. With the help of this forum it took me 2 weeks of dragging out leaves, vacuuming, and shocking with up to 6 bags of CalHypo per day, and 1/2 a bottle of floc to get the water almost perfect and crystal clear.

But now, I have a scum line that won't scrub off just below the return where the swampy water sat for 2 years. It's a 2 inch wide band almost like a perfect stripe. I've brushed it a couple times and looks better, but now it doesn't seem to want to come off. The rest of the liner looks nice and clean. Please tell me there's a fix to this other than getting a new liner.

Thanks!

Two miracle drugs, Chlorine and Persistence, may very well get that stain off.

I doubt anything will remove it immediately, but trying a few things and the continued exposure to the Cl in your water will probably minimize it to an aceptable level...maybe even make it go away.

I have seen several products recommended here on the forum but I have not tried any of them. Others will be along who have.

PS - Nice work on your water...numbers look good.

Have you tried the Mr. Clean Magic Eraser by chance? I get the black film on the skimmer box and it takes it almost completely away. Might be worth a try you haven't already...