I know that by code "The drainage system of the building must be vented by one or more pipes whose combined cross sectional area is at least equal to that of the largest required building drain line.
So..... I've got a 4" building drain and two 3" vents through the roof which means I'm good to go. But does that mean I need to vent one of my fixtures like a shower or toilet with a 3" vent all the way to the roof? Or can I just vent it with 2" and use a pipe increaser at the roof to connect to the 3"?
So..... I've got a 4" building drain and two 3" vents through the roof which means I'm good to go. But does that mean I need to vent one of my fixtures like a shower or toilet with a 3" vent all the way to the roof? Or can I just vent it with 2" and use a pipe increaser at the roof to connect to the 3"?