Sewer smell while driving

[sc180b]

Originally Posted by DIAPERMAN

The shower is grey water and stool is black tank I think I found problem access panle in bathroom there is a releif valve that runs in the side top of black water tank the one-way valve on it is bad but Fleetwood dose not show on parts list

What is on the nontank side of the relief valve? Is the relief valve threaded into tank or is part of the tank? Is the odor in the bath room or in the front area of coach?