I have a 3-pc rough-in in the basement I want to finish.

The part that's confusing me is the pipes coming out of the concrete and how to vent properly. Aside from the obvious toilet drain, there's two pipes coming out of the concrete in the corner where a tub or shower would go and 1 pipe coming out of the concrete where the vanity would go. There's also a hanging capped off pipe coming down through the floor from upstairs, which I assume is the vent I need to tie in to.

I basically need a "how-to" on finishing this bathroom. I know already that I need to break up the concrete and move the shower drain out for my 38"x38" corner unit. I'm assuming one of those pipes is a drain and the other is a vent. I just don't know how to plumb up the vent lines here.

Hey Dan,
It's tough to figure out what's under the slab without being on site but I'll give it a shot.
The two pipes in the wall look like the one inside the wall vents the tub/shower and the other is the drain that you'll be moving to pick up the shower. There will be a wall built to cover the lavatory drain and vent pipe and the stack with a clean out,(don't cover the clean out up when you drywall.) The capped pipe is, no doubt, a vent through the roof.
The lavatory will have a 2X 2 X 1 1/2" sanitary tee installed 18" off the floor to the center of a stub-out. Come off the top of the tee with a 2" vent pipe that will tie back to the shower vent and both will connect to the capped vent pipe. This vents your bathroom group. Is this what you wanted to know? Good luck, Tom

I believe this is exactly the questions I needed answered. So just to clarify, the sanitary tee off the lavatory drain would have the sink drain coming in on the 1-1/2" and then 2" connected to the drain going into the concrete and off the top 2" would be a 90 degree elbow and then a horizontal pipe with another tee in it that the shower vent would come across to meet, then off the top of that tee would be a 2" to meet the vent stub up top?

Thanks for the quick response!

You got it! The vent friom the lavatory will come out of the tee and go up in to the rafters before connecting to the shower vent where each will tie together and connect into the main vent through a INVERTED TEE. (that's a Sanitary Tee turned upside down)
Good luck, Tom

Agree with Tom . Good job identifying rough-in...