I have used a grout cleaner called bathroom Floor Grout Cleaner by Finazzle with great success on WHITE grout in our bathroom. It too was not sealed and since it was the main bath it tended to get gray fast. This is probably the easiest stuff I have ever used and it does not have the strong odor that bleach has. On the bottle the internet site is finazzle.com. GOOD LUCK. P.S. After you first do a test allow it to dry completely as the results are not true until then.