Basement Rough In

I have a three piece rough-in in my basement that I would like to finish. The right and left pipes (Tub on left and Sink on right) are 2" and a 4" (toilet) in the middle. Currently there are no walls installed. The wife would like to make the bathroom almost 8' wide. That would put the back wall 6" from the tub drain, 18 1/4" from the toilet and 7 7/8" from the sink. I plan on moving all three almost straight back. The tub calls for a 9"x12" drain welll in the concrete with the drain centered 4.5" and against the wall. The toilet will be 12.5" from the wall and I will put the sink drain in the wall and plumb to it from the sink. Does this make sense? As for venting. When the builder built my house, they capped off a 1.5" pipe about my HVAC ductwork not too far from the bathroom. Can I assume this is a vent? Will a 1.5" vent for for all three fixtures? My neighbor mentioned that when he had his basement done, they vented just the tub and sink to the 1.5" vent and the toilet was wet vented. Does this make sense? Do I need to run a separate vent for the toilet?

Any help would be appreciated. Is my plan workable? Should I consider something else?

Thanks in advance,

Jim dePrado

I can tell you that you're a better man than me. If I read your post correctly, that's a lot of work to gain less than a foot of width in a secondary bathroom. What with tearing up a perfectly good slab with concrete saws and hammers and ripping out a perfectly good rough-in I might be more inclined to lose a little space and spend the money on dinner for the wife and having a plumber come in to tie on to the vent after I got the walls up.

Just an opinion, possibly colored by the fact that I've been spending way to much time with a 70lb demo hammer lately.

Good luck!

-Sam

Dunno about your codes, but here a minimum 2" vent is required for a bathroom group.