Motorhome Maintenance with Mike (PT.5)

Odiferous Issues

Even luxury coaches can sometimes have a sewage smell permeate the cabin area of the motorhome. The offensive odor can most times be traced to the holding tanks. The contents of those tanks just naturally smells bad and nothing you do to them will change that fact . You can put chemicals in till the world ends but nothing is going to make sewage smell good...better or less offensive maybe but never "good".

It is necessary to vent these tanks to the atmosphere in order that they can accept more contents. They have to "breathe" more or less. This is almost always done by running a vent pipe from the tanks through the roof of the vehicle and thus, get the offensive smells away from our noses. Those same smells would come back up through the drains if it were not for the curvy looking pipe just below the drain. You can see those "P" traps by looking under your kitchen or bathroom sinks. This device holds water in the "U" shaped part and that water prevents odors from traveling back up the drain and into the room.

Problems start when the water is not present in that "P" trap. NO water means odors can and will come out of the drain. Water can disappear several ways...It can leak out which should be obvious, it can evaporate over time if the coach is not used, or it can be "sloshed" out from traveling rough roads. Because of space limitations, some drains use fairly shallow traps, like under showers.

When traveling there is normally some pressure in the tanks depending on the location of the roof vent pipe. If someone flushes a toilet while in transit, the pressure is released UP through the toilet and then when the toilet flap is closed that fluctuation in the tank pressure can cause the water in the "P" trap to be pulled into the tank allowing ventilation of the tanks to the interior. At this point the occupants usually start opening windows which exacerbates the problem.

The cure: every so often just run about a half a cup of water in every drain. Don't forget the shower and the washing machine. Anytime a commode is flushed while in transit, run the water and remember, the gray water tank stinks too!

Mike M. 

Motorhomes of Texas