This is the most common thing we hear on tile jobs in Duluth, Johns Creek, and Sandy Springs: the floor gets mopped faithfully every week and the grout keeps getting darker anyway. The homeowner assumes they're doing something wrong. They aren't. The mop is the problem.
Tile itself is glazed and non-porous, which is why it wipes clean so easily. Grout is the opposite. It's cement-based and full of microscopic pores, so it behaves like a sponge running in lines across your floor. When you mop, you loosen dirt off the tile surface and suspend it in the bucket water. Then you put that water back down. The tile sheds it. The grout drinks it in.
That's the whole mechanism, and it's why the pattern is so consistent: shiny tile, dark grout lines, getting worse every month. Each mopping deposits a little more into the grout than it takes out. Doing it more often makes it worse, not better.
Scrubbing by hand with a brush and a grout cleaner does genuinely work — we're not going to pretend otherwise. The catch is that it's brutally slow, it's hard on your knees and back, and you still have to get the dirty solution off the floor before it dries back into the lines. Most people manage a bathroom this way and give up on the kitchen.
What we use is a sealed spinner tool that does both jobs at once. It sprays cleaning solution under pressure — enough to drive it into the pores and lift the soil out — and vacuums the dirty water straight back up in the same pass, before any of it can settle. The dirty water leaves in the machine. That's the part a mop can never do, and it's why the difference is so obvious in a single pass across a floor.
Sealing afterward is worth considering. A penetrating sealer fills the pores so spills sit on top long enough to be wiped up instead of soaking straight in. It doesn't make grout bulletproof and it does wear off over a few years, but it buys you a lot of time and makes routine mopping far less damaging. We can seal grout right after cleaning, while it's clean and dry — that's the only sensible time to do it.
If your grout has gotten away from you, it's almost certainly recoverable. Call (404) 503-6288 and we'll take a look.