My re-grouting project. 3 days of sweat equity and $100 in tools and materials.

The water was seeping into sub-floor from the Master bath. I had to let it dry for 6 days then use dremel to remove the old grout which took more than a day, grouting, drying, sealing and polishing off took 2 more days. For now bath room is back in use. Hiring a pro would have cost $1200.

If any one wants to re-grout, be prepared to spend 10% time shopping, 70% removing old grout, the deeper the better 5% applying grout and 15% cleaning, polishing tiles and overall cleanup. Much easier to do on a horizontal surface like counter top or bath vanity but the walls can be tough. You may give up and do re-model instead.

I used a Dremel 300 series tool I had long ago like this one
with a grout removal bit
and grout removal kit

I ended up destroying both the grout removal bits by the time I was done.
What I found was that the guide was not really smuch of a help once I got the hang of using the grout bit.

Walmart now sells a Dremel 3000 series now

Final photo below.