New toilet plumbing

[MICHAEL55]

I am adding an upstairs master bath in a small room connected to the master bedroom. There is a wet-wall containing plumbing for an existing upstairs bath and existing downstairs bath. The existing upstairs and downstairs toilets each have their own wastepipes to the main drain in the crawlspace. Can a new toilet connection be added to the vented vertical wastewater pipe that serves the downstaires toilet or would this be a no-no? If not, can a 2-way toilet arrangement (one on each side of the wet-wall) be installed on the vented upstairs vertical wastepipe?

[sqbuilder]

I am not sure where you are but almost all areas have codes on this matter, and for good reason. You could end up flushing one toilet and pulling the water out of the other, or overloading the existing diameter drain pipe or draining in to an unsealed vent line. Venting is needed for each fixture, not like in the older homes where one vent covered everything. My advice is to get some bids from reputable liscensed plumbers. Good luck , Joe.