So you have put in your new tile floor or re-tiled your bathroom shower. No what? Before you get to comfortable with your new tiled space make sure to seal the grout so it's protected and stays clean. Sealing your grout is basically adding a protective barrier to your sanded grout lines. This prevents staining and cracking of the grout over time. It's not normally done with a new tile installation, so if you have a professional tile setter installing tile and grout ask if they seal it afterwards.
In most cases they don't seal it. Even on new construction. I have dealt with a lot of newly constructed homes in Tampa FL and very few have had grout sealing done. Home owners usually don't even know this is an option. As a professional tile and grout cleaner I always including sealing the grout lines with every cleaning to ensure the home owner gets the most out of their clean grout.
If you plan to seal the grout yourself make sure to get a water based penetrating sealant. Penetrating grout sealers do a better job of protecting your grout than non penetrating sealers. Sealers that sit on top of the grout are called grout coatings and they have a much shorter life span. They wear down easier and they have a tendency to be tacky and can collect soils. I don't recommend coatings unless you use a grout coloring epoxy which is good for about 15 years.
Grout sealing is a great way to maintain your tiled surfaces and reducing cleaning labor in the future. In Tampa FL its a must have when getting tiling done in your home.