J.H. Holliday wrote:

I've got a very old tiled shower stall that has grout rather than caulking
on the joints between the walls and the floor. The grout is breaking off and
I need to re-seal.

Should I remove the old grout and use caulk instead-- or try to re-grout?




Remove the old grout. Make it absolutely clean - no soap scum, etc.
Wipe with denatured alcohol, let dry. Wipe with full strength bleach
immediately before caulking (let it dry). Use silicone caulk.
Corners are caulked rather than grouted because walls/floors expand and
contract or move as house settles, which cracks grout.