I know there are a few of us on here who are obsessive about cleaning. One of my biggest peeves is dirty grout, which I can never seem to get as clean as I'd like.
WELL, I've found a miracle! If you mix baking soda and hydrogen peroxide together to make a paste (personally, I like mine of medium consistency), let the mixture soak on the grout for a few minutes, take a firm bristled cleaning brush and scrub, then wipe off with warm water- you will see the cleanest grout, ever! (and all very inexpensive.)
Anyway, just thought I'd share.
Best,
Rachel