Sewer odor in trailer

louiskathy wrote:
I think it's a vent issue. You're dumping and that can cause the water in the "p" traps to be drained...allowing odors into your rig. More with the black tank than the gray I would guess. I put about 3" of water in the bathroom sink in our rig before we dump. That way, when we're done dumping, I just pull the stopper and put water back into the sink's drain.

I make sure I turn off all the ceiling vents but opening a bathroom window when you are putting a hose down the toilet to hose out the tank will bring up some bad odors.

Check under the kitchen sink - some rigs have a vent pipe there.
Check the vent on the roof, make sure that's not clogged.

That's about all the suggestions I can come up with from my experience and what I've read on this forum from others.

Kathy is on the right track........

The black tank doesn't have any 'P' traps......just the vent line to roof, dump line from toilet and drain line.

You don't have odors in rig (normally) so your toilet bowl seal is good (holds water), the toilet floor gasket is good (no odors normally).
So sewer odors could be coming from vent pipe on roof and getting sucked back in thru bathroom exhaust vent, open windows in rig, fantastic vents etc.

Grey tank odors can be as stinky as black.
Under the bathroom sink and kitchen sink could be an air admittance valve. They are installed on a short stub pipe (just screw on) downstream of 'P' traps. They are there to stop the water in 'P' traps from getting sucked out when draining grey water tanks.
They are inexpensive and do fail. If they don't open properly the 'P' traps can get sucked dry allowing grey tank odors back inside.
And if they stick open they provide a direct path from tank to inside of rig.