I am having trouble balancing my 36ft x 18ft inground pool. I had water analyzed and copper content was 3 ppm, I used several lb containers of acidic stain metal remover and they did not work I also have a large black blob shapped stain near the deep end that nothing can remove it.
What can be done to remove the stain from our vinyl liner and get our water balanced. I use chlorine capsules in the skimmer to chlorinate plus a shocking once a week with pool life Zap It/ I use about 5 pounds. I also put in 40 lbs of baking soda to get ph up and it is not going above 6.8.