For some reason, I'm really struggling to get an intuitive understanding of drain venting.
What if a house had 3 stories, one toilet on each floor, all connected to a vertical 4" main stack (which properly vents through the roof). Does this installation require separate vent connections?
It seems like it should - if the 3rd floor toilet is flushed, doesn't the bolus of water potentially create high-pressure air below it, blowing out the trap of the 1st floor? I'm confused because I've seen diagrams omitting venting in this arrangement.