Grout lines are formed from the grout between tiles from installation. The grout is a very important part of tile installation process because it helps to keep the tiles in place. It also helps to stop dirt and debris from falling in between the tiles. However, the grout lines themselves can get pretty dirty and discoloured over time. Luckily, you can seal the grout lines to help protect them against discolouration.
Remove any loose debris from the crevices of the grout using a wet/dry vacuum. You can also scrape away loose debris using a stiff cleaning brush. Scrub the grout with a hard back and forth or up and down motion, depending on the direction of the grout line, to loosen and remove debris.
Mix together one gallon of water per two cups of bleach in a bucket. This mixture will be used to bring back the natural colour of your grout, which is important to do before you protect it against discolouration. Otherwise, you will be sealing discolouration into your grout.
Scrub the grout using the bleach mixture you created. Instead of using a wide cleaning brush, use an old toothbrush. The toothbrush will allow you to get into the crevices of the grout and restore the entire surface with ease. The stiffer the old toothbrush is, the easier it will be to get the grout back to its original colour.
Fill a spray bottle with plain water. Spray down the grout and tile to rinse away the bleach cleaning solution. Place a towel on the floor to catch the water and solution that drip down, and dry the tiles and grout with a cloth. Wait a day before sealing to make sure it's completely dry.
Apply the grout sealer. You can purchase grout sealers at local hardware or home improvement stores. Silicone grout sealer in a spray bottle or with a sponge applicator is easiest to apply. With a spray bottle, simply spray a fine mist over the grout and tile. Once it's dry, the grout will be sealed and protected against discolouration. With a sponge applicator, squeeze the bottle gently to release the grout sealer and rub the applicator directly into the grout. Again, once it's dry, your grout will be protected.