[mn1247]

I have a question about Air Admittance Valves. My understanding is that, if I use an AAV, I still need at least one conventional vent to the roof.

Just wondering why this is. I realize it's required, but what happens if the conventional vent is absent?

Thanks
Eric

 

[DangerMouse]

Pressure. If all you had was AAVs, the pressure has nowhere to escape to.

DM