I swear the tile pros said before the best way to clean the tile (and maybe grout was with a steam mop). I also believe they said bleach will break down the grout over time but maybe use it once if it worked and then maintain with the steamer?

Thanks so much for the ideas. The thought of scrubbing each grout line is enough to make me cry. Or enough to say, who CARES if my grout is dirty?!?!

Mix up some bleach 50/50 with water. Use a brush and agitate it over the floor, liberally. Let it sit a while and brush it again. Flush it out with clean water and sin no more.....

Did you ever get it cleaned? I just bought a house and have the same issue. The role and grout is new (last decade) but dirty in spots. I am going to try a McCulloch steam mop.

Do not use bleach please, look into renting A Vaporlux 5000 steam cleaner, start w diluted white vinegar and dawn dish soap mix. Steam mops dont have the gravitas....

Also curious how this is going 4 years later? about to lay similar tile!