Venting question.

Obvious but tired.
3.5 bathrooms and i vent stack.

What makes it worse is 2" inch ( master bath ) PVC is taped into a 2" PVC off tyhe main 3rd floor bath, then expanded into one 4" PCC 12 inches before the exit through the roof deck.
Washer dry , powder room with shower cabinet.
1/2 bath on first floor.
Kitchen with island and double sink.

here is the 4" enlarged PVC fitting and exit.

Not proper and not allowed you can end up with a bath exhaust discharge circling in the home and none of the moisture vented to the out side .

All require there own discharge to the out side .

The 2 inch is just another incorrect concern .

Take a look.
Engineered vent stacking.

Sorry I was still a sleep I thought you where talking about Bath room and Kitchen power exhaust vents .


The black pipe is ABS and increase to 4 inches in unconditioned area to prevent frost closure.

They covered the ABS stack with galvanized as it exited the roof.
Metal will conduct cold faster than ABS.
No main waste ( wet stack ) in the attic. Only venting.
The main wet stack can not be seen Marcel.

That is the only venting exiting the roof.
I thought the main waste or wet stack must continue through the unit exiting the building through the roof, not the wall.
Link please.

Individual fixture vents need to be at least 1-1/4", branch vents need to be at least 1/2 the corresponding branch drain size and sized for the drainage fixture units (typically 2" pipe), there needs to be at least one vent thru the roof, and the size of the vent on the exterior needs to be at least 3", where subject to freezing, with that transition at least 12" below the room. See IRC Chapter 31 or Code Check for an HI’s POV. Your local mileage may vary … :wink: