My house was built in 1983 and has only 1 DWV pipe exiting the roof. All the vent pipes from 3 baths and 1 kitchen are 2 inch and are tee'd into 1 3 inch stack vent. But I live 6 miles outside the city and county builder codes may have been different back then.
YMMV.
Retired, US ARMY 1973-1994
ASE mechanic, Electrical 1994-1997
Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
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