[JABURKHOLDER]

I don't, under normal usage, have an odor problem. I usually use what ever chemical is on sale at the time. My problem comes when I am dumping/cleaning the black tank. To be clear...I DO NOT do anything with the toilet itself. The flush valve in the toilet stays closed. Everything I do is from the convenience center. I add water to the tank via the tank flush inlet then open the dump valve. I do this process a few times watching for clear water at the sewer hose. I also back flush the tank where the sewer hose attaches. Again, I never go inside and operate the toilet. During this cleaning process I get sewage odor throughout the rig. The only path that is open for odor is the roof vent, through the tank then out the sewer hose. Nothing internal to the rig. The roof vent is not plugged because I can smell the stinky stuff venting when I am on the roof. The vent is located near the front ac unit. Now I am not sure how the ac unit works but when running does it draw in outside air ? And if it does, why do I only have the odor when I am dumping/cleaning the tank ?
Thoughts ?