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.