lanerd wrote:
When stuff is flushed, it should not allow any sufficient amount of air to come back up as the pressure it creates should cause the air to go up the vent...not up the toilet at the same time. That's the whole purpose of the vent.
Something is not computing here and it sounds like maybe your vent is not operating as designed. Perhaps the pipe is sticking too far down into the tank and is being blocked when the tank is full or nearly full. Just a guess on my part, but I do suspect you have something that's not working correctly.
With all due respect, I'm not trying to argue with you...just trying to point out that maybe you might look at this from a different angle.
Ron
Perhaps there is a fan on that creates a draw and odors come up thru the opening when flushing.
What temps are you in? The tanks gets VERY smelly in 90-120 temps very easily.
Also think about the fact the bowl has a 3" opening and the vent is 1.5". Path of least resistance.