Tom,

I've been scouring the Internet for diagrams of what you've described as a "typical bathroom group" -- and the only one I've found so far is this:

http://i228.photobucket.com/albums/ee112/jameslrice/14040_72_2.jpg

I notice in this diagram, everything appears to be tied in to the main stack. What happens if there is another bathroom group on a higher floor that is also tied into this stack? Is it up to code to utlize the stack this way for a lower-level bathroom, or does a separate vent have to be installed?

What happens if there is another bathroom group on a higher floor that is also tied into this stack? Is it up to code to utlize the stack this way for a lower-level bathroom, or does a separate vent have to be installed?
This drawing shows a first floor bathroom. If there was a second bathroom over it draining into the same stack the first floor bath would have to run a separate vent. Regards, Tom