Greetings! I'm hoping one of you Master Plumbers out there can answer a question for me.

I'm going through the code book and I understand that it's a no-no to put a sanitary tee on its back. I can understand why this is forbidden if the vertical connection is a drain. A combo would be the solution for that scenario.

What a don't understand (and maybe my understanding is flawed) is why can't you use a sanitary tee on it's back if the vertical connection is a vent? This would be a crown vent, right? And a crown vent, as long as it's more than 2 pipe size diameters away from a trap, is allowed... am I still correct?

Thanks in advance for sharing your vast knowledge.