18-29-912.3 Size.
   The minimum size of a combination drain and vent pipe shall be in accordance with Table 18-29-912.3.
Table 18-29-912.3
Size of Combination Drain and Vent Pipe
(for Floor Drains Only)
Diameter Pipe (inches)
Maximum Number of Drainage Fixture Units
Connecting to a horizontal branch or stack
Connecting to a building drain or building subdrain
Diameter Pipe (inches)
Maximum Number of Drainage Fixture Units
Connecting to a horizontal branch or stack
Connecting to a building drain or building subdrain
2
3
4
2 1/2
6
26
3
12
31
4
20
50
5
160
250
6
360
575
 
For SI: 1 inch = 25.4 mm.