: I'm installing a basement bathroom on conrete. I want to "tap" into the DWV drain without busting up the floor. The toilet has a hole in the floor for it, so that is no problem. For the shower stall, I built it up on a base to put a trap under it. The sink and shower I want to drain into the same pipe just above the floor. The pipe I'm "tapping" into is a 2" dwv pipe. The main drain is 4" where everything is currently draining. The 4" pipe is not near where the bathroom is so I want to use the 2" pipe. Is this 2" pipe only for venting, or is it OK to run the shower and faucet into?

A shower and a lav can drain into a 2" pipe. Without seeing your 2" pipe, it would be hard to tell. It depends on whether it is considered the vent, and possibly plumbed in a way that precludes using it as a waste pipe. It may be possible to "wet vent" in some situations. Your local codes will determine whether it would be allowed in your case.