Mallard M26 bad smell

Hi all, first time RVer here. We are in our third trip with our new Mallard M26 and it seems like we continually get a sewer smell that is strong around the bunk house and under bunk area.

We do have our black and grey water open because we are hooked to sewer, but our black water tank shows 2/3 full this evening.

Has anyone else experienced this? Any ideas?


Sent from my iPhone using Tapatalk


Would start there all of your sinks and shower have p-traps like your house keeps the smell from entering the house. Your toilet is directly into the tank.
That makes sense. Thank you. This is only my third weekend out with this and I am a new owner. I appreciate the help.

Sent from my iPhone using Tapatalk


Well-known member
When we hook up to sewer we leave both black and gray water valves closed. First we don't like pyramids forming but the grey water aids in flushing out the plumbing after the valves and the drain hose. If I have to drain the grey tank during an extended stay I close it again and to allow the grey tank to fill as much as possible for this purpose. Also be aware leaving the valve open invites the little gnats from a sewer system into your tanks.


Well-known member
I use to leave our grey tanks open but recently ran into two issues. First was we were getting a bad sewer smell from the vent under the bathroom sink, and washer area. I am assumed that the campground was having a ventilation issue causing gasses to build up.

The second issue was when I watched a maintenance guy a few campgrounds ago try to fix a sewer backup by shoving a hose down the sewer line and flushing the lines out. The backup must have been downstream somewhere causing water to gush out all of the sewer connections. I quickly ran over and shut our grey tanks. Everything just stays closed now until it needs to be emptied!