Tile and grout
Grout doesn't go gray because it's old. It goes gray because it's porous.
High pressure cleaning that pulls soil out of the grout lines and takes the color back toward what it was laid at, with sealing available afterwards to keep it that way.
Why grout looks worse than the tile around it.
Tile is close to non-porous, so it wipes clean and stays that way. Grout is the opposite. It's a cement-based line running between every tile, and cement is porous enough that soil, grease and mop water work their way into it a little at a time. Mopping moves dirt around on the surface of the grout without pulling it out of the pores it's already sitting in, which is why a floor can look clean and the grout lines can still read gray or brown. That's a color problem hiding as a dirt problem, and it needs more than a mop to fix.
What high pressure cleaning actually does differently.
We run the same truck-mounted system used on carpet, adapted for a hard surface: high pressure water forced into the grout line lifts out what's been packed into the pores instead of just moving it around on top. On most jobs that alone takes the lines back several shades toward the color they were laid at. If you want that result to hold, sealing is available as a follow-on step, since a sealed grout line is far slower to re-absorb soil than a bare one. Either way, nothing in the process involves soap or the residue that comes with it.
Dirt Free, family owned in Houston since 1989. Call (713) 730-2782.
Kitchens, entries, and bathrooms
These are the three rooms grout problems show up worst in, since they carry the most foot traffic and the most grease or moisture. If the same visit needs to cover carpet elsewhere in the house, or the counters and floors are natural stone rather than tile, say so when you call and it gets booked as one trip instead of two.
As with every job, ask about the free test spot first. Grout responds fast enough that a single line usually tells you what the whole floor will look like.