Is it a 36F as you say or a 35F because what you are describing is the 35F layout. Either way at www.winnebagoind.com you will find the complete plumbing schematic.
As an owner or a 35F, I have, on occasion, noticed a slight sewer odor in that compartment. It is never strong enough that I have had to investigate aside from checking the hose connections. The half bath toilet sits directly atop the black tank. If you have the same setup there is a dump valve, macerator pump and tank in the compartment.