Once it's good and dry, apply a coat of masonry sealer so that it won't absorb dirt in the future. Also, once the cleaning is done, rinse the area well to remove any traces of bleach. If you have colored grout, you should clean it with a heavy-duty cleaner and a grout brush. You'll want to be sure not to use a bleaching solution on colored grout. A masonry sealer can be applied to clean, colored grout to ward off future stains.
Phosphoric acid works well and is safe for most surfaces.
If you buy cleaners containing phosphoric acid in a grocery store, it will likely contain about 4 percent to 6 percent acid. You can purchase lime scale removers at janitorial supply stores that contain 8 percent to 12 percent acid, which will get the job done faster. A higher concentration of acid is safe on most household surfaces as long as you rinse the surface to remove all traces of the acid once the cleaning is complete. You should let acid sit for a few minutes after you apply it to let it work. Tough hard-water deposits may take more than one application.