My basement was roughed in for a bathroom when they poured the slab, the shower drain is a 1-1/2 pipe coming out of the floor in concrete block imbedded in the concrete with gravel in it... my question is that about 20" away from this is another pip coming out of the floor, Im assuming this is the vent pipe, but its do close to the shower drain that it will interfere with installing the shower... can I put an elbow on this and reroute across the floor to the wall, and up the vent, or does it have to run straight up from the floor??

Hey Chucker,
First you have to be sure the second pipe is really a working vent.
You are not going to break cement and put it under the floor? Yes you may offset over to the wall and out through the roof or revent back in the attic and no it doesn't have to run straight up from the floor Once it's against the wall you may cut in a 1 1/2 Drainage tee 18" off the floor and install a lavatory and cabinet and be vented for both fixtures. Good luck, Tom

The vent pipe I spoke of is already in the slab... it was all roughed in when they poured the slab... I will also be putting in a sump pump... the basin was roughed in when they poured the slab, toilet drain, lavatory drain are all there, I just can't figure out why that vent pipe would be so close to the shower drain, I will prabally build up a base for the shower, and route the vent under this and up the wall.

If the basin was already roughed in then the vent for your group runs off the basin. It has to, otherwise the basin would be "S" trapped which is outlawed. Vents aren't roughed in in the center of the floor unless the plumber missed a wall. Now you don't have a choice. You're going to hafta find out why that pipe comes up out of the floor and what it's supposed to pick up. Let me know what you find out. Chers, Tom

So now I think that the 2or 3" pipe coming up near the toilet and against the wall must be the line that will run to the sump basin, and the pip I thought was a vent must be my lavatory drain... starting to make sense now, does this sound right to you?

Whoa! This is the first I've heard about a sump. When I told you the basin vented your group I thought you meant a lavatory basin. Where is the lav stubout?
The vent runs up from there. You're going to have to find out exactly what each pipe is for. Until you do you're flying blind. Let me start you out. The toilet is a 3 or 4" pipe 12" out from the wall. The lavatory should be in a wall and I would fell a lot better if the shower drain were 2" instead of 1 1/2". What kind of a sump are you puttingt in? Where aill the pump set and what kind of a discharge pipe will be used? Back to square one!