I am going to be replacing my old plumbing in the basement bathroom. Well, part of it anyway. My house was built in 1951. The basement bathroom sits directly below the bathroom on the main floor. The room is finished, but there is a cutout in the wall directly above the sink to allow for this cylinder/can thing which is connected to the upstairs bathtub drain line & overflow line. What is this thing, and what can I replace it with? Ideally, I would like to be able to re-route the line so that it is hidden behind the wall. Can anyone help me?
Thanks, Alex in Colorado

Sounds like a drum trap.

Replacing it with a p-trap is going to be a very involved procedure.

Growler's bang on. You have a drum trap connected to your tub. You replace the drum trap with a "P" trap by cutting out the drum trap and coupling on a piece to get you over to the tub waste and over flows tail piece where you will install and connect the "P" trapo. Good Luck, Tom