I tiled my bathroom and grouted it around Christmas time. I have used the shower already and have no problems. I have noticed that the Grout has been breaking off in some sections of the floor and I have noticed some small water coming out from the grout as I step onto some of the tiles. (Did some plumbing work and there was a puddle of water from that) and the crout is crumbling in some areas. I stopped using that bathroom and have waited for the area to dry out. It wasn't a lot of water as there was no leakage issues on the floor below.

My guess is that I didn't pack the grout sufficiently in some areas and there is a problem there. I'm guessing that is also could be thinset or subfloor related. Subfloor seems fine, I chipped old tile away from it and it was in good shape (have done this many times before).

Does anybody have any advice. The area is dried out, I planned on cutting away bad grout areas and regrouting. Can I just cut away old grout and patch without touching the unaffected areas?

Thanks for any help.

It's possible that you're right and it's just a bad grout job in that area, but, it doesn't sound like it to me. The problem is in the shower floor right?

Grout will not crack unless there's movement. You confirmed movement when water squished up when you step on the floor. Those tiles are loose. I can't tell unless you tell us exactly how you install the job. Try tapping the tiles with the handle of a screwdriver and listen for hollow sounds.

Jaz