Brian Henderson wrote:

The shower hardware in one of our bathrooms is 40+ years old and is
leaking like mad. I got all new replacement hardware but the old
piping is so coroded that I can't take it out. I've sprayed about 3
cans of Liquid Wrench on the connections to loosen them and no go. I
could cut them out, but since it is impossible to replace the lines
going up to the shower head and to the faucet, and I couldn't remove
the piping from those two connections... I'd be up a creek.

Any ideas? I'm tired of banging on the two pipes with a pipe wrench,
I just want to get it all replaced.

Is this galvanized iron pipe?? Are there unions??
No idea what your arrangement looks like but one method is
to heat the fitting with a torch to expand it.
Or cut the galv and rethread it.
Or use a Dresser compression fitting.

Jim