Why Does My RV Smell Like Sewer When Driving and How to Fix It? 

In most cases, you won’t smell sewage while driving an RV unless it’s a motorhome. However, for whatever reason, anytime you’re driving your motorcoach down the road, the smell of sewage becomes evident and unbearable. What you can’t figure out is why does your RV smell like sewer when you’re driving but not at other times? 

Your RV smells like sewer when driving down the road because you have waste and sewage in your black tank that you forgot to dump and it’s getting stirred up and releasing odors as you bump down the road, or you don’t have water in your p-traps and there’s nothing to block the smell of sewer gases. 

While these are two of the most common reasons for sewer smells while driving, there are more to come. In this article, we’ll delve into each possibility and how to repair it to get your RV smelling like itself once more. Let’s dive in! 

If the following reasons don’t solve your problem and your RV just smells like sewer in general, check out this article for more tips.

6 Reasons Your RV Smells Like Sewage While Driving

Sewage in Your Black Tank 

The first and most obvious reason your RV smells like sewage while driving is because you have a dirty black tank. The black tank is responsible for holding the poop, urine, and other bodily wastes that go into your toilet. While there are vents and seals in place to stave off the smell of sewage, these odors will inevitably rise and enter your RV while you’re driving because of the stirring action it creates. 

How to Fix 

There are several ways you can remedy a dirty black tank. 

1. Perform regular black tank flushes with fresh water. 
2. Treat your black tank every other week with an RV Black Tank Treatment. 
3. Travel with a clean black tank, but leave several gallons of water in the tank to block smells. 

No Water in P-Traps 

Another likely problem area is in your p-traps. Every plumbing fixture in your RV, showers, sinks, and lavs has a P-trap in the drain line. These traps are designed to hold small amounts of water that block sewer gas odors. However, as you’re traveling, this water can wash backward and go down the drain, which means there’s nothing to block sewer gases and the smell they produce. 

How to Fix 

If you suspect empty p-traps are the source of your odors, dump a cup of water into each sink and plumbing fixture. Restoring water to the p-trap will help them do their job of blocking sewer gases. 

Faulty Air Admittance Valve 

Depending on the age and type of RV you have, it might utilize air admittance valves instead of rooftop vents. Air admittance valves are installed on each plumbing fixture and designed to open and close when they need to release sewer gases. However, it’s possible for air admittance valves to get locked in the open position, resulting in a backflow of sewer gases. 

How to Fix 

If an air admittance valve is faulty, you’ll most likely have to replace it with a new one. 

Ineffective Sewage Vent Cover 

In most cases, RVs will be equipped with rooftop vents instead of air admittance valves. Unfortunately, vents are prone to blockages and defects that will interfere with it doing their job. If a vent is blocked or the vent cover isn’t sucking air upward, sewer gases won’t be able to escape your RV and will cause a stink. 

How to Fix 

1. You’ll have to climb on top of your RV to check your sewer vent. 
2. Remove the vent cover and use a flashlight to peer inside. 
3. If you see a blockage, you’ll have to remove it. 

It’s also possible that your vent cover isn’t effective at pulling gases out of your black tank. Factory vent covers are fairly cheap and often don’t do an excellent job of this. If that’s the case, replace your vent cover with a new, more effective one. 

Your AC is Drawing in Sewer Smells

A problem we’ve run into from time to time is that the air conditioner pulls sewer smells back into your RV when driving causing your rv to smell like sewer. If, for example, your air conditioner is downwind from any of your rooftop vents and the AC is turned on, it will pull air into your RV directly out of your vent pipes. This will inevitably cause a huge stink. 

How to Fix 

If your RV only smells while driving if the rooftop AC is turned on, it’s likely the source of your problem. You can either turn the AC off or put up with the smell and leave it on. 

Bad Toilet Seal 

Finally, the bottom of your RV toilet may have a bad seal. Like house toilets, there’s a seal on the bottom of the RV toilet that keeps water and odors from escaping when you flush the toilet. However, if this seal starts to give out, it may still retain water, but it won’t be able to hold in sewer gases. 

How to Fix

If your toilet seal is giving out, your RV will probably stink all the time, not just when driving. However, the motion of the moving RV may be enough to stir up sewer gases that only escape the toilet seal when you’re driving. If this is the case, you’ll have to remove the toilet, replace the seal, and re-install the toilet atop it. 

Improper use of Black Tank Chemicals

You will always need to add chemicals to your black tank to help break down the solids and organic material, here is our favorite toilet additive that will leave your black tank smelling fresh.

Frequently Asked Questions 

Why does my RV smell like urine?

If your RV smells like urine, it may be a bad toilet seal, or it could be just dried up urine on the bowl. For more details on how to troubleshoot, here is a full article on the topic that will solve your issues.

How do I get rid of sewer smell in my RV?

To get rid of a sewer smell in your RV, you’ll have to find the source of the smell and repair it. 

Why does my camper smell like sewer after moving?

The most likely reason that your camper only smells like sewer while you’re moving is because of a dirty black tank. The motion of movement stirs up sewer gases, which amplifies a dirty black tank. 

Why does my RV air conditioner smell like sewer?

If your RV air conditioner is downwind from a vent pipe, it will suck in sewage gases from the pipe and circulate it through your RV.