Cleaning a dirty grout is a tough job, but here's a tip that could make it easier...

  • 3 cups baking soda into a medium-sized bowl
  • 1 cup warm water
  • Mix into a smooth paste and scrub into grout with a toothbrush or grout brush
  • Rinse thoroughly

(I have tried this recently and it works brilliantly! Image is not my bathroom....)