wrote:
Looking for advice on whether I need to add a vent to the waste line
downstream of the toilet (~3') where the new shower will tie in. A few
feet upstream from the toilet is the sink and the vent for the waste
line tees in there . I'm figuring I need to but I'm going to have to
move a heater and wreck some sheetrock on the other side of the wall if
I do. Any ideas?
Thanks Rick

Yes, you really should tie the
shower drain back to the vent stack,
downstream of the shower trap.

But...in this case, you might get
away with a mechanical vent or
"air-admittance" valve:
http://www.studor.net/

Oatey makes one too.

If it matters, find out if the town will
accept a mechanical vent.

Jim