I have a Hover FloorMate and about 500 square feet of light beige tile with off white grout. I like the way the machine cleans the floors. The way I keep the grout clean is to use a little homemade liquid soap in the grout lines before cleaning, just squirt a little in the dirty looking places let sit for at least 5 minutes, then run the machine as usual. Done and back to quilting in less than 30 minutes.