I am blessed/cursed with an awful sense of smell.
Cleaning up cat vomit? It’s a blessing.
Grandma brings the pumpkin pie out of the oven? It’s a curse.
A sharp sense of smell is your first defense when diagnosing severe problems with your RV. These scents are clues that can help you sleuth out the source of a malfunction or infestation.
So put on your trench coat, blow out that sniffer, and let’s track down common RV smells and what they mean.
Table of Contents
Burnt, Acrid, Smoky
Does your RV smell like you lit a plastic bonfire?
A smoky, acrid smell is often caused by an electrical short, arc, or loose connection.
Caution! Electricity is very dangerous! Electrocution can seriously injure or kill you. Disconnect your RV before beginning any electrical inspection!
- Start at the power inlet. Check the contacts of your power cord and power inlet for any black smudges or pitting, which would indicate arcing. This can be caused by low voltage, which is why you need a surge protector!
- Next, inspect the converter. Check all the circuit breakers and fuses, again looking for black or brown streaks or the smell of burning plastic. Also, carefully feel for warm areas or contacts, which would indicate higher resistance.
- Make sure all the wires are tight! That includes wires to the breakers as well as the neutral and ground wires. A loose neutral could be the cause!
- Learn everything you wanted to know about converters.
- Then, check out your house batteries. Look for damage at the battery terminals, shortstop circuit breaker, and battery disconnect switch.
- The problem might also be a loose wire to one of your appliances. The most common culprit is probably the air conditioner, either the compressor or blower fan.
Unfortunately, electrical issues can be some of the most difficult to track down. Your best friend is a multimeter (or RV mobile technician).
Musty, Damp, Mildewy
Does your RV smell musty or damp? Maybe like wet newspapers or sweaty socks?
Bad news: That means water.
The big question is: Where is that water coming from??
The most common cause of a musty RV smell is poor ventilation during storage. Humidity can easily work its way into an RV, but it can’t easily work its way out. In severe cases, the air inside the RV can be so humid that it condensates at night, causing rain inside the RV itself!
The fix is simple: Air it out and run a dehumidifier as long as you need to! Ventilate the RV while in storage, or at least use a desiccant.
Ah, the stuff of nightmares: A leak!
Water leaks will cause a musty smell because of mold or mildew.
Leaks can be internal or external.
- Internal leaks typically come from your freshwater distribution system, such as a loose swivel PEX connection or busted, frozen pipe.
- External leaks often come from unsealed roof penetrations, windows that don’t shut properly, and rain-driven wind through appliance vents.
Here’s some great information about how to stop RV leaks before they happen. And here’s my recommended list of RV caulks and sealants for just about any application.
Mold or mildew can grow on just about any surface, although they prefer organic materials like wood products.
Common locations for mold in an RV include:
- Back of cabinets
- Underneath the sinks
- Behind the shower
- Along the roofline at the roof-wall joint
- Around the front door beneath windows
- Around the base of the fridge
- Around the air conditioner opening
In severe cases, mold will even generate its own heat! If you place your hand close to the back of a cabinet and feel heat (combined with a distinct musty smell), you probably have mold growing in the walls.
Learn how to deal with mold (and other RV indoor air quality contaminants) at my mini Ebook here.
If you’ve ever owned cats, dogs or kids, you know what pee smells like. If the RV smells like urine … well, if it walks like a duck and talks like a duck …
Animals often use the corners of RVs as their private urinals and litter boxes. Start looking in corners for red, yellow, or green stains. Don’t be afraid to use your sniffer!
And never trust anyone who says, “This RV has never had an animal inside of it.” You have no way of knowing if they’re telling the truth.
Decaying Fish, Sweaty Socks
Also described “dirty gas station bathroom” and “decomposed mustard,” the smell of ammonia – well, you won’t forget it.
An ammonia leak means you have a defective refrigerator. There’s an ammonia leak in your refrigerant lines. Look around the base of your refrigerator for any yellow stains.
Repairing a malfunctioning absorption refrigerator isn’t easy. You’ll need to have the fridge professionally serviced or replaced.
If your RV smells like wet paint, I’m guessing A) it’s a new RV and B) it’s hot outside. RVs are typically built with materials that off-gas VOCs. Most of this off-gassing happens during the first few months, and heat accelerates the process.
What you’re smelling are VOCs and evaporative solvents. Let your RV air out following the process I discuss in this article.
If you’re chemically sensitive, here’s a guide I wrote just for you!
Does your RV or “toad” smell like burning rubber?
At the risk of being Mr. Obvious, if you’re smelling “burnt rubber” after driving, it’s probably an automotive problem: oil leak, worn drive belt, failing transmission, overheated brakes, etc.
It’s a common phenomenon that a toad vehicle (like a Jeep) will smell like burning rubber for a few miles when driven after being towed.
The consensus is that road grime builds up on the exhaust system of your toad vehicle. Because the exhaust stays cool, the grime accumulates. When you fire up the engine, the heat burns off the grime for a few minutes, which emits a burning rubber smell.
Like Something Died
If what you’re smelling reminds you of that time you walked by a dead deer on the side of the road and almost died yourself, then you’re probably dealing with the same problem, but in miniature.
More than likely, you have dead mice. Mice can wriggle through a hole so small your pinky finger can’t even fit!
Start the body recovery process by looking in drawers, in cabinets, and underneath the bed. Hopefully, Mr. Mouse passed on while exploring an easy-to-access corner of your camper, or inside the furnace compartment (they like warmth).
But if the mouse is stuck in the walls, ductwork or roof, good luck ever getting him out. Thankfully, in a few weeks, you’ll be able to breathe again. He’ll return to the dust from whence he came eventually.
If your RV smells like poop, you’re not wrong.
Obviously, something has gone astray.
- Most likely, sewer smells are escaping into your living space through a leaky ball valve in your toilet. That valve can be replaced quickly for a song and a dance.
- The wax or rubber toilet seal between the base of your toilet and the floor may be bad, too. You might need to re-install your toilet with a new gasket.
- It’s also possible that your black tank vent pipe is broken, disconnected or blocked, and the smell has nowhere else to go. Check the vent on your roof! (and install a siphon/cyclone vent while you’re at it).
- You might have too much sludge in your waste tank (I’ll let you figure out what “sludge” means). God willing, you didn’t leave your black tank drain open and inadvertently created a Poo Pyramid. You need to thoroughly clean your tank, and from now on, put 5 gallons of water into your black tank before using it!
Rotten Eggs, Sulfur
The classic sulfurous rotten egg smell is one of the most common bad smells inside an RV. It has several possible causes.
1. Boiling Battery
Overcharged flooded lead-acid batteries can release hydrogen sulfide, which is a toxic, flammable gas. This is rarely a problem with today’s 3-stage smart converter/charger, but it can still happen with old batteries, antiquated converters, or improper charge settings.
Be very careful around an overcharged battery! If it explodes, you’ll wind up in the hospital with third-degree acid burns all over you. If the smell is strong, you see steam or smoke, or the sides of the battery housing have swelled, just shut off the power and STAY AWAY FROM THE BATTERY!
2. Water Heater Anode Rod
Many water heaters (not all) use an anode rode as a sacrificial corrosive component. When the anode rode finally bites the dust, you’ll start to get a sulfurous smell in your fresh water. Simply replacing the anode rode in your water heater and sanitizing the system should kill the smell.
3. Propane Leak
Propane is naturally odorless. For safety reasons, mercaptan (a harmless gas that smells like rotten eggs, rotten cabbages, or dirty socks, depending on your preference) is added for odor detection.
- If you smell a propane leak, hopefully, you’ve heard about it way before! The propane alarm in your RV, which should be mounted near floor-level, should have started beeping a loooong time ago.
- Propane leaks are typically at the stove, where someone left a burner on without a flame.
- Another possibility is a loose connection when the main manifold (flex hose, copper, or black iron pipe) connects to an appliance.
4. Bacteria in the Water Tank
If you stored your RV with water in the freshwater tank, it’s probably turned into a mini-civilization of different bacteria. And it stinks.
You need to sanitize your fresh water system. You can do this a couple of ways, but the easiest is to add ¼ cup of bleach for every 16 gallons of water. There’s a whole process after that (letting the water sit, pumping the system, etc.), but that’s beyond the scope of this article.
5. Nasty City Water
If you’re smelling sulfurous water when cold and connected to city water, then it’s not your fault – it’s your campgrounds! Contact the campground host and immediately alert them to the problem. Don’t drink the water. Hopefully, you brought some back-up bottled water!
- Psst . . . if you’re reading this content anywhere besides Ask The RV Engineer, it’s been illegally “scraped,” and you’re probably on a spam website. So please be careful! Don’t share any private information, and come back to us at www.askthervengineer.com!
Uh oh. You might have stink bugs.
Halyomorpha halys is an invasive insect that reeks when squished or scared. They’ve been known to establish entire cities inside RVs, especially around appliances with outside vents (furnace, water heater, refrigerator).
Get the help of pest control. Stinkbugs can multiply faster than rabbits and literally overrun your RV. You can get rid of a few bugs by using Dawn soap, water and a puck light. Severe infestations might require bug bombing.
If you’re detecting a garbage-y odor, a stew of odorous decompositions and offgasing, you’re probably smelling a dirty gray water tank.
This is definitely true if the smell is coming from the sink or shower drains.
People commonly assume that the black tank is the worst offender, but gray tanks can pack just as powerful a punch.
Your RV either has P traps or waterless valves to prevent gray tank sewer gases from infiltrating your living space. If your P trap dries up (common during storage) or water sloshes out (common on rough roads), then gray tank gases can escape.
Also, some sinks have air admittance valves (AAV) rather than being directly connected to a vent pipe. AAV’s allow air into the drain system, preventing a vacuum clog. Anyway, a broken AAV won’t seal, and stink escapes.
Living in a stinky RV is no fun. If you don’t want to wind up back at this list in the future, follow these three rules:
- Religiously clean your gray water and black water tanks.
- Properly winterize and sanitize your fresh water system annually.
- Use insect screens and expanding foam to keep all critters, bugs and rodents outside where they belong!
P.S. For more tips on getting rid of RV odors from a full-time RVer, read our other article here!