[header] How to clean tile and grout [title] Assemble the necessary tools. [substeps] A grout brush that is made to go down into the grout while you are standing up. A hand held pump up sprayer (it does not need to be chemical resistant) a mop of some kind to remove the slurry you will create (or a wet/dry vacuum) the proper alkaline or acid grout cleaner.
Do not try to get the most aggressive acids or alkaline chemicals. Find an approved cleaner, perhaps at a local janitorial supply house.