There is a brown bathtub like ring around our new IG vinyl liner pool, and it is located at the wateline. I think it is dirt and oil?- probably residue from the construction. PB says he will clean it off, and mention using muratic acid. I guess he would dilute it? He cautioned about using other cleaners- says they break down the liner. He also says suntan lotion will break down the liner. Is that correct? What is safe to clean exposed liner and fiberglass steps? Thanks, Web