Hello, I've been reading posts on this forum and found it very useful and educational. Finally decided to join.
I have inground, 30000 gallon pool, vinyl, cartridge filter.
Initially had problem with metal stains. Solved this with ascorbic acid treatment followed by Natural Chemistry Metal Free. Worked great but stains returned couple weeks later. I'm on my secound acid treatment plus now has coolator 4ppm in the pump basket.
With all of the above said, there are still a few of dark elongated stains at the shallow end that won't dissapear. Almost look like the liner is "burnt" there, like a permanent stain. Any ideas?
Thanks a bunch