Awful sewage smell on return trip

Driving with a vent open in our RV will cause negative air pressure in the living space. Negative air pressure will pull fumes from the tanks into the RV. We get the same thing if we run both power fans on "exhaust" without opening windows too.

Could be a restriction in the gray and black tank vent(s).

I have a Max air vent cover on my bathroom fan and used to leave the vent open all the time. My black tank roof vent is in front of the Max air vent by about 2 feet. When I drove down the road with a partial or full black tank, the stink came out the roof vent and right in the Max Air vent into the trailer. I no longer tow with the bath roof vent open.

They do make a deodorizer for the grey tanks. Just a little down the drain each trip really helps. I've had the same bottle for years, not sure where I got it - probably Camping World or Wally World.

I would go with grey tanks and empty p-traps. We have the empty p-trap problem on some roads.

evanrem wrote:
I make it a point now to fill all my traps with water when I get home. I also add some water to the black tank a dump the chemicals in. Problem solved for me.

Best advice I could give. I have experienced dry, smelly traps by simply moving from one site to another in the same camp ground traveling less than a mile at a crawl. It doesn't take much movement to break the seal in a trap.

I make it a point now to fill all my traps with water when I get home. I also add some water to the black tank a dump the chemicals in. Problem solved for me.

I would think it may just be the motion stirring it up, and not enough water in the tank to cover the "smelly stuff". Sometimes ours will smell if we dump it, and don't run some water into the tank again.

Could be grey water sloshing around and a dry ptrap in the tub letting the fumes come back up as well.... that stuff stinks baaadddd!