This is my 16th year opening my pool. Three days ago I did what I do every year. Began filtering 24/7. Vacuumed sides and bottom. Changed DE 3 times. Water got clearer every day. Today it was very clear. There was some dark residue on the bottom of the deep end, so I vacuumed it away this afternoon. But there are some dark spots (streaks) that won't vacuum up or brush away. These spots were not there this morning. I've never seen anything like it.
I never have algae problems. I've kept the Cl >2 since the start (3 days ago). I put a lot in to keep it there, which I do every year. Today the solar cover was on all day. I took it off, vacuumed the deep end like I said, and the black areas are there.
The liner is 10 years old.
Any thoughts? What could this be? I can't include a photo right now because it's too dark.
I never have algae problems. I've kept the Cl >2 since the start (3 days ago). I put a lot in to keep it there, which I do every year. Today the solar cover was on all day. I took it off, vacuumed the deep end like I said, and the black areas are there.
The liner is 10 years old.
Any thoughts? What could this be? I can't include a photo right now because it's too dark.