To get an answer to this question, I of course first used a google search,
which offered up this whopping gold mine:

http://groups.google.com/groups?q=%2...oints%22%20sho
wer&hl=en&lr=&ie=UTF-8&sa=N&as_qdr=all&tab=wg

Okay, so I did some more searching on the web as well, but basically, the
picture I get is that this has been a divided issue.

Not much of a sampling to get any clear picture though.

Every place I have lived here in the Ohio Valley has used grout in the
verticle corner seams of a tiled shower, yet the guy at Home Depot said to
use caulk. Some on this group have said to use caulk. Others, grout. Has
anything improved on the grout front in recent years that might change any
opinions? Also, I'm doing a repair job of just a portion of the shower
wall, though it does extend to the corner joint. If I were to grout, could
I just grout over the old grout that remains in the portions that didn't
require repair (and which seems in good shape)? Or should I knock out all
the old grout and then caulk? Finally, how about leaving the old grout in
the untouched portion of the verticle joint, grouting the repair portion
(sanded since it has a large fill area behind it), letting it cure for a
week or so (perhaps hanging plastic over it when shower is in use), and
then going back and caulking over it?

Hell, I don't know. Chime in.

Thanks.

Oh, p.s.: This shower is in a rental unit. The porcelin or enamel or
whatever it is on the tub is worn and its beginning to get rust. The whole
thing needs to be torn out and replace with a wall unit, but I would have
to tear out walls around it to get the unit in. So really I just need
something to hang on for three or four years until I can remodel the whole
bathroom.