Thanks to my Dremel rotary tool and their 1/16" Carbide Grout Removal Bit (see at Amazon.com), I now have the failing grout in my downstairs tile shower stall removed and ready for repair.
The photo to the right shows where the grout removal bit had been used – the horizontal line – versus the vertical grout line which was hit with only a putty knife and grout saw. As you can see, the rotary tool bit does a great job of cleaning out the old grout and leaves a clean area that’s ready for new grout (after the dust was vacuumed out).
This photo shows the corner that I believe as the cause of the leak into the basement. This photo was taken before I took the Dremel power rotary tool to it. At the time this photo was taken, I had only used a putty knife to clean the grout line. You can see where the far corner tile popped up out of the floor. This was actually good news because it proved that this area was the trouble spot because the back of the tile was wet. (Enlarge the image and you’ll clearly see that there was obviously a problem around the parameter of the that missing tile.)
Having that one tile out also meant I had a little more room to dig into the back corner to remove old grout. This photo shows the grout lines after I used the grout removal bit to clean out the vertical corner grout, the area along the floor, and to the vertical wall grout to the far right.
After all the failing grout was removed, I vacuumed the area and then started thinking about how I wanted to tackle the grout replacement. More on that next time.