I have a 2010 Winnebago Adventurer 35P. When we start traveling after using our coach in a campground we get a horrible sewer smell throughout the entire coach. We open some windows and the smell goes away in about 20 minutes. I have replaced the vent covers under both sinks, and I make sure there is water in all the traps. It happens on empty, partially full or full tanks. The shower vent pipe has a cyclone vent cap on the roof. We get no sewer smell when parked. What should I look for next? —Ted
The two under-sink vents you replaced we call “cheater vents” and are for the gray water. They should not produce a sewer-like smell. Here is the drawing from Winnebago’s website on those vents.
Might need to sanitize the gray tank
Since they are under a counter, the vent pipe cannot go all the way to the top and out the roof. so they use a “syphon cap”—which I am not a big fan of. Again, since this is the gray water that has the shower drain, it should not have a sewage smell. However, you might try sanitizing the gray water tank just in case. I have seen a few units that had a terrible smell from the gray water that sat for a long period of time with grease from the kitchen sink.
Here is the diagram of the toilet and vent pipes that go to the top of your unit.
There are grommets and couplers that could have come loose or even cracked at the top of the tank. These vent pipes are most likely hidden in the bathroom wall. You might have to take the paneling off to access and inspect them. If they are cracked, or just came loose, the cyclone vent will actually draw the odors out of the tank and they will escape inside the rig.
The smell could be from the toilet flange
Another issue could be the toilet flange or grommet, as seen in the exploded circle of the above diagram. Take off the plastic base and make sure everything is connected firmly. Check if there is any odor coming from this.
This should all be a closed system. Therefore, if there is an odor coming inside, I would believe there is an open area in one of the vent lines and the cyclone is pulling it into the coach. Another thing you could try is to have the tank empty, close off the cyclone vents and test drive down the road. If there is not a smell, you have your answer.
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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