sewer odor

Are you sure it's not the grey tank? As Doug indicated, it can smell horrendous. Sometimes the P-traps slosh and lose their seal. Try installing stoppers when traveling and see if the problem goes away.

Put a Pint of Pine Sol in your Gray tank and then drive. If you get Pine Sol odor in transit it is your Gray tank. RARELY do you get foul odors from the Black tank, especially if you use the Black tank treatments as you need to do. GRAY water smells horrible. Make sure your Washer drain P trap has water in it if you have a washer. If you do not use the washer regularly, the water siphons out and that is a main source of gray odor in transit. Doug

My bathroom odor was from the clothes washer drain hose sticking into the pvc drain too far, displacing water in the 'P' trap. I raised the washer drain hose and fastened it to keep in out of the trap, and no more odors.

mine was the seal on the commode.

gbopp wrote:
Could the odor be from a faulty air admittance valve(s) under the sink?
The odor from a gray tank can be just as nasty as a black tank.

+1 on the faulty air admittance valve.

Could the odor be from a faulty air admittance valve(s) under the sink?
The odor from a gray tank can be just as nasty as a black tank.

Also you can put a water hose down the vent and ensure your flow of water is going into the tank. Need two people for this.

Do take a look at the vent but normally there would be a venturi effect while driving, that pulls the odors out the vent.

A damaged vent could be negating that effect...or if there is a blockage, you might get odd airflow out of the tank.