Phos-Clean Bowl and Tile Cleaner contains 20% Phosphoric Acid cutting through hard water scale, lime, rust or soap scum deposits with ease without damaging surfaces or chrome fixtures. Phos-Clean is formulated to provide cling that allows it to stay in contact with the areas to be cleaned longer which provides better cleaning with less effort. Phos-Clean will clean grout back to its original clean appearance. Apply Phos-Clean directly to the grout, let sit for 10 minutes, agitate with a brush and rinse with fresh water. Let dry and the grout will look like new.