Is this super dirty grout?
My tips for Easy Grout Cleaning:
Pre-Treat for Easier Cleaning: I used a product called Grout Master, but Zep Grout Cleaner works great too. Let it sit for 5-10 minutes to loosen grime before scrubbing.
Use the Right Tools: A stiff-bristled brush or an old toothbrush works wonders on grout lines. For larger areas, I recommend the KeFanta Grout Scrubber from Amazon. Plus it's on a pole so you don't have to bend over!
Rinse the Dirt Away: Use a traditional bucket and mop with warm water. Make sure to switch out the water when it gets dirty to avoid spreading dirt around the floor.
Seal to Protect: Once clean and dry, apply a grout sealer to prevent future stains and make your cleaning efforts last longer. I like to use the grout sealer from Tilelab.