Good thing bad thing

[down_home]

We all know not to run a vent fan when flushing the toilet..unless a window is open and maybe not then.
We've encountered some sewer systems wit a positive air pressure, usually those that are just tanks that have t be pumped every little bit.
We are on a normal hookup with n problems. The pipes etc are all good.
Never notice this before but with the vent fan on and gray tank open we were getting sewer smell. Hadn't been leaving a window partially open because it had been rather cold.
Nice to know the coach pert neer air tight...but gonna have a window a bit even if it is raining cat and dogs.

[ScottG]

Yes, AAV is defective. One of the cheapo's that came with our new TT started leaking gasses on our last trip.
At least it was an easy fix.

[Lynnmor]

Check to see it the smell is coming from the air admittance valve usually located under the sink(s). Replace with a good one from a home improvement store. I wouldn't keep any drain valves open to the entire campground sewer system.