The line does run to both the tub faucet and the shower head. When I bought the place flow was constricted, had to use a low flow head. I'm figuring at this point this means having someone rip out the wall, and I probably might as well redo the entire (small but only full) bathroom the way it should have been done in the first place to address various other concerns. I had hoped to avoid this until I could buy a second house and move first, but then rates jumped.

Thanks for all your input!