Shower plumbing in exterior walls?
My wife and I are remodeling our master bath, including a redo of the shower. The shower is your standard 3-walled enclosure, but two of the walls are exterior walls. We want to put in dual shower-heads which means one of them will be on an exterior wall. Can anyone tell me what sorts of issues we'll need to deal with in order to run the supply plumbing for valves, showerhead, body-sprays, etc. in an exterior wall?
Some additional info:
* We're in Austin, TX so the temperature only rarely drops below freezing, and then not by too much.
* The exterior wall studs are 2x4's, not 2x6's
* The plumbing lines will come from the attic space above, down through the wall header, and into the wall cavity.
The local plumbers we've talked to have said there shouldn't be any issues, but they've also encouraged us not to apply for permits and/or involve inspectors, so I'm not super comfortable with the situation.