Sewage smell

[BobA]

I have a sewage smell coming from the back of my RVision Condor Motorhome. I did everything. Cleaned out tank, Put conditioner in tank, went for a ride with ice cubes in tank. I did find a plastic tube hanging down from under the tank, looks like someone cut end off. Any ideas.

[Spk64]

Check under the sinks. If smell is worse in that location then may have an AAV under there that needs replaced.
Some other potential sources.
AAV in a wall cavity sometimes behind showers.
Backflush anti-siphon valve if you have tank rinse connection.
Plugged roof vent.
Roof Vent with a bad seal allowing gases to get in under the roof.
Sink Traps that have dried up or sloshed out while driving.

[britcon]

Could also be coming from Grey tank. Sometimes they smell worse than black.
Try deodorizing that one.

[strongcity]

We have had this problem and have always found it to be the gray tank. I always drain the gray tank at home before leaving on a trip.

[mtofell]

I use to get bad odors on my new 5th wheel until I filled the tank completely and let it sit for a couple weeks. All I can figure is the transport guy dropped a dookie and it stuck to the side. Filling the tank and letting it sit dissolved it off the tank surface.

[ThePowells]

Bob, if you are just now finding that hose isn’t an issue but not a bad idea to find out what it goes to. You wasted your time and effort doing the ice thing. As was mentioned before, check your AAV under your sinks as a possibility. Second would be a cleaning cycle. My preferred method would be to turn on the LP to the water heater, then I run hot water with Pine-sol and Dawn into the black tank until the water runs warm. Then I let it recover and do the same with the gray tank. Then let traffic provide the agitation. Others may use a different cleaner, but the end result was the same. Weekend before last, we were in Pa and SWMBO decreed that the black tank was full since a Poo pyramid was visible. I drew a diagram of the tank design and tried to explain, but rule #2 was invoked and the valve was pulled. I had to go in with a water hose and nozzle to break that one up and the valve became very hard to move ( valve, not bowel). After getting the solids and semisolid out, I left the cap on and the valve open and put in my solution. The valve freed right up. I left it closed and drained the stuff into a pan then hooked up the slinky.

[GRedman]

We had the same problem. Put a little deodorizer or bleach in all your sinks. Grey water is every bit as offensive.

[Quincy]

Don't rule out a leak in the black tank. Good luck and keep us posted.

[Gary RVRoamer]

Don't rule out failing batteries either - many people mistake that sulfurous smell for sewage odor.

[pumper9x9]

Check you automatic vent valves under the sinks. If you have a washer run it to make sure that there's water in the P trap. If you have no washer and it's plumbed for it make sure that the drain pipe has a cap or auto vent on it.

[BCRVer]

How do you test the automatic vent valves?

[donnyman]

This maybe obvious ...but.... do you have water in all the p traps? sinks and tubs, ask me how I know!

[Rossi6998]

Is this a new motorhome? Check the vent pipe where it connects to the black tank. When my motorhome was built, they did not properly seal it.

[bandmbrown]

Had same experience...vent pipe plugged. Went on roof and cleaned it out down to tank.