Earlier this year I had my concrete deck covered with pavers and the coping stones around the pool are fixed with some type of mortar. What I beleive may be some form of calcium deposits have appeared beneath the coping stones on the tile which is between 12 inches and 20 inches above the water line. Today I have powerwashed the tiles and have successfully removed some of these white marks but others still remain. How do I remove these unsightly stains and should I seal the coping stones and if so what type of product should I use?