How do I clean the line at the water level around the inside of the pool?
If this is at the water line of the pool it sounds like what we call a scum line and can be easily cleaned with a pool product called Tile and Vinyl cleaner which you spray on and then wipe off. This works well also for the top of a Vinyl liner that is supposed to be white but usually has some mold right at the top where it goes into the coping. Just be careful not to use a hard wired brush or anything abrasive. I have also used Sodium Hydrogen Carbonate (Alkaline Increaser) using a wash cloth or sponge and it cleans the line nicely as well.
