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There is a Sewer Smell in Our Motorhome While Driving

by Dawn
(Traveling in Texas)

40" Fleetwood Revolution RV has sewer smell only while driving how do I fix it?

ANSWER: Hi Dawn thanks for submitting your question on our Ask An RV Question Page

The bad news is that this is a common problem that RVers experience. The good news is that in most cases there are some simple steps you can take to stop the sewer smells from entering your motorhome while going down the road. Below I have listed the most common causes and remedies for a "Smelly Motorhome".

No Water in P-Trap Each of the sinks and showers/tubs in your RV have a P-Trap (see picture at the top of this page) just like the sinks and showers/tubs in your house. The curved part of the P-Trap is designed to hold water and prevent holding tank fumes from entering the RV from the drain. The problem is if there is no water in those p-traps holding tank gasses could be sucked into the motorhome through the dry drain.

If you drive your motorhome with windows or vents open it can create a suction in the RV almost ensuring that holding tank fumes will be sucked into the motorhome through a dry sink or shower/tub p-trap.

Solution: Before traveling make sure that you dump some water in each of the sink and shower/tub drains in your motorhome. If this does not cure the problem move on to the next step.

Bad Air Admittance Valve You may have Air Admittance Valves on your RV's Sinks (see picture at the top of the page). In some motorhomes an Air Admittance valve is used on RV sink in place of having a roof vent on the sink. The way an air admittance valve is supposed to work is when you run water in the sink you create a vacuum which opens up the valve on the air admittance valve to allow water to freely flow into your RV's holding tank.

Occasionally these valves get stuck in the open position allowing holding tank gasses to enter the motorhome.

Solution: To fix this problem you need to install a new air admittance valve on the affected sink. The air admittance valve will be under the sink and attached to a stub from the output side of the sink drain. You simply unscrew the old valve from the pipe and screw on the new valve. If this does not cure the problem move on to the next step.

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Replace Sewer Vent Cover/s: In some cases it may be necessary to replace the factory vent covers on your RV with ones that will effectively draw holding tank odors out of the tank to the outside of the RV while traveling.

Solution: One of the most effective and highly rated of these vents is the Cyclone Sewer Plumbing Vent manufactured by Camco Manufacturing (see picture at the top of this page). The Cyclone Sewer vent costs less than $20.00 and can be do-it-yourselfer installed. Take a look at the video below to see how the vent works and how easy it is to install.


Again the tools you will need are:

* Utility and Putty Knife
* 100% Silicone Caulk
* Drill with a 3/32 drill bit
* Phillips Screwdriver

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Other Less Common Causes of This Problem:

* A bad seal on the RV's toilet
* A broken, cracked or disconnected holding tank vent pipe
* A cracked or leaking holding tank
* A cracked or broken pipe under a sink, shower/tub or toilet

I hope that this information has been helpful to you.

Do you have any suggestions or comments on this topic? You can add them to this page by clicking on the "Click Here To Post Comments" link located near the bottom of this page.

Happy RVing

RVing Al

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