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8 Reasons Why Your RV Toilet Smells And How To Fix It

Kelly Headshot

By Kelly Beasley

Published: December 10, 2021

Last Updated: August 15, 2022

The toilets in recreational vehicles will not emit any odors when working correctly. However, there are certain circumstances when you can smell the sewage stored in the black tank.

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Whether the RV toilet smells when flushed or if you get the sewer smell when it's scorching out, there are ways to eliminate an RV sewer smell.

Should My RV Toilet Ever Smell?

Not really, but at some point, you could have an RV black water tank odor.

The good news is that the way an RV toilet system is constructed usually prevents any stench from penetrating the cabin.

The construction looks something like this. This applies to any recreational vehicle, be it a travel trailer or a motorhome. The RV sewage tank is usually mounted underneath the RV, as near to the RV toilet as possible.

Pipes connect the opening of the toilet to the interior of the black water tank.

Camp Addict travel trailers parked in storage

Additionally, the tiny amount of water that gets trapped in the toilet bowl when the flush valve closes after you flush keeps any waste holding tank foul odor from penetrating the RV interior.

RV black water tanks should have a vent pipe that leads from the tank's roof to the top of your RV. This helps the sewage drain down the sewer line and into a dump station while allowing methane gas to escape outside of your camper.

Woman leaning out RV door

So, RV toilet smells that come from the sewage it holds should never get inside when the system is working correctly.

That said, if you DO have an RV toilet smell, there is a reason. Figure out the cause, and there is always a fix to stop the toilet odors.

8 Things That Can Make Your RV Toilet Stink

There are eight possible black water tank problems that can make your RV toilet smell. You must figure out what the problem is before you can remedy the situation.

Here are the most common reasons and their remedies:

1. Bowl Seal Not Sealing

Just like a sticks and bricks house toilet, RV toilets have a seal at the base that disallows any leakage onto the floor.

If this seal is broken, your camper smells like sewage, almost guaranteed.

The Fix

The fix should be self-explanatory. Replace the seal, and your RV sewer gas smell should immediately disappear.


2. Blocked Black Tank Vent Pipe

Every RV black tank has a vent pipe that goes from the top of the black tank up to the roof of the RV. This is to allow gases to escape and vents the tank when dumping.

The waste tank vent pipe can get clogged. Be it mud daubers or something else; if it's clogged, you'll get a horrible smell coming into the RV when you flush.

The Fix

Run a garden hose into the roof pipe. Turn on the water. Make sure the water drains into the black tank. If it backs up and comes out of the pipe, the waste tank pipe is clogged with some solid waste.

The water may unclog it. If not, try using the garden hose to push the clog through. If that doesn't work, get creative or take it to an RV service center.


3. Leak In Sewer Pipe Or Broken Black Tank

There could be a crack in the sewage line leading from the toilet to the black tank. Also, there could be a crack in the black tank itself.

My advice here is to get rid of the RV. LOL! I'm kidding.

Anyway, unless you can see the sewage waste dripping out at the leak point, this can be one of the more challenging problems to figure out.

The Fix

Best case scenario, you find the waste leak and can patch it. Worst-case, and this is the more likely case; you should take your RV into a service dealer. Sewage waste a very messy job that can go very wrong.


4. Clogged Black Waste Tank

This not-so-rare problem is a real pain in the butt to take care of. The clog is often due to using not enough water and putting too much RV toilet tissue down the tank.

Using regular toilet paper or using too much toilet paper most commonly causes a stoppage in your black waste holding tank.

If you didn't know not to leave the RV black tank valve open when parked with a sewer connection, you'd have the notorious 'poop pyramid' clog.

What happens with a poop pyramid is that gravity pushes the liquids down into the sewer. At the same time, the solids (poo and toilet paper) remain behind, forming an eventual pyramid that plugs the tube coming down from the toilet. A leaky waste tank will have this same effect.

The Fix

The pile of poo must be punctured so that you can get water through. Once you have unblocked it (can try using a bendable tube) fill it with water. Then, drive around a little to shake/stir things up. Then try dumping again. Repeat until it works.

You can also try using tank treatments explicitly made for breaking through a clog. However, this might not work on the most stubborn clogs.

Lastly, you can try using an RV black tank flush system to flush out the clog. One that goes down into the toilet is probably the most effective type. As long as you can get the apparatus through the clog and down into the tank.

If none of your methods works, get professional help.


5. Your Toilet Is Dirty

This is the easiest fix of all. Some RV toilets don't rinse particularly well. If that's the case, the urine smell accumulates pretty quickly and turns rancid right there in the toilet bowl.

Look under your toilet seat, too. Sometimes there's a buildup of urine there. Keep that toilet clean, and you won't have odors.

The Fix

RV owners, this is so easy- clean your RV's toilet! Be thorough about it.


6. Toilet Flange Seal Is Not Working

This one is pretty easy to diagnose. If your toilet is not holding the little puddle of water in the bowl between flushes, your toilet flap seal is leaking.

This is what stops the RV toilet odor from coming into your RV. Once the seal is broken, there's nothing stopping the odors from coming in.

The Fix

You can remove the seal and try cleaning it off and maybe moisturizing it. Replace it and see if that fixed the leak. If it does not, you should replace the seal gasket—a cheap and easy fix.

Note: On some toilets (such as Thetford) you have to disassemble the toilet to get to the seal. If you are going to this trouble, just install a new seal. They are cheap and you don't want to be disassembling your toilet more than you have to.


7. Hot Weather

There's something about camping in sweltering weather that causes the black tank to reveal itself in the worst of ways. It has to do with the heat causing the bacteria to go overboard in production.

The more the bacteria digest, the more gases they produce. The more gases they make, the smellier it gets. Sometimes it seeps into the RV.

The Fix

Get an odor-destroying treatment for your tank and use it consistently. We like Happy Camper RV tank treatment for eliminating odors in your 'sewer system.'


8. Leaving The Roof Vent Fan On When Flushing

This is the easiest of fixes. And this mistake is one you probably won't make more than once! The lesson comes hard and fast.

If you have a ceiling fan such as a Fantastic Fan or Maxxair Fan, ESPECIALLY if it's right there in the bathroom, TURN IT OFF before you flush.

Otherwise, once you flush and open the opening to the black tank, the toilet smells will immediately get sucked up out of the waste tank and into the entire RV.

It's horrible, and the camper smells that come from it are hard to get away from once they enter the living area of the RV.

The Fix

Turn off the roof fan before you flush the toilet!


FAQs About Sewer Smell In An RV

If your camper smells like sewer, something is going on that needs correcting. Any holding tank odor existing inside the RV living area indicates a problem.

Airstream travel trailer parked at campground campsite

Here are some questions with answers plus ways to avoid having camper toilet smells in the first place.

Why Does My RV Bathroom Smell Like Sewer?

Your RV bathroom may smell like a sewer for several reasons. The possibilities are listed above.

Be aware that your gray water holding tank might be the culprit of the tank odor.

Why Does My RV Smell Like Rotten Eggs?

If your RV smells like rotten eggs, you likely have one of these three problems:

  1. Your hot water heater needs to be cleaned out/anode replaced.
  2. You have a propane leak. Find it and fix it ASAP.
  3. Overcharged lead-acid battery. The battery is probably bad and should be replaced.
Truck Camper

What Causes Sewer Smell In My RV?

There are many causes of why your RV toilet smells like sewage. We list them above. Here are some preventative measures for how to keep your RV toilet from smelling.

  1. Clean your RV toilet regularly to avoid a smelly RV toilet. Give it a good scrub. Use some toilet bowl cleaner. Also, always rinse the bowl well after urinating.
  2. Use an RV septic tank treatment or chemicals to avoid bad smells.
  3. Don't put your toilet paper down the toilet, OR be sure to use septic-safe toilet paper. Your RV doesn't have a septic system, but it DOES hold sewage. TP is the biggest factor in RV tank clogs in most cases.
  4. Add plenty of water to the bowl, especially when you go number two. The more water, the better.
  5. Do an occasional cleaning and flushing of your black tank to deep clean and possibly eliminate unpleasant odors.
  6. NEVER have your roof vent fan on when you flush your RV toilet. This causes big-time RV toilet smells when flushed. And your tiny home is a very small space- that tank odor can easily encompass the entire RV quickly! It's something you will likely only make the mistake of doing once.

Why Does My RV Shower Drain Smell?

If your RV shower drain has a nasty stink, it may be time for a good cleaning. If cleaning doesn't help, you're probably RVing in high heat.

High outside temperatures can cause the black and gray tank to become so stinky it seeps into the cabin area.

Kelly's RV shower

We recommend finding a good liquid or powder biodegradable RV holding tank treatment made to kill odors.

Treat both tanks for RV black water tank odor control as well as gray RV holding tank odor control.

Toilet paper roll on top of RV toilet

My RV Toilet Smells When Flushed. Why?

Often this happens if you leave the roof vent fan on while flushing.

If that's not it, your black tank vent pipe could be clogged. See above how to check for a vent pipe clog.

Kelly's Opinion On Why/How You Don't Need Any Tank Treatment Unless For Odor Control

So, I RV'd full-time for 5.5 years. Full-on full-time, it was my only home, and I only boondocked, stayed in a campground fewer times than I have fingers.

At first, I used Happy Camper tank treatment. However, I stopped shortly after hitting the road. Why? There are a few reasons.

Looking Into The Black Tank

Not everyone can, but I can see directly down into my toilet's black tank. I flush, the flapper opens, and bam, my pipe leads straight down. So, with just a flashlight, I can see the inside of a small section of the bottom of the tank.

Interestingly, while dumping, I would go inside and flush for a few seconds or more to get any last bits out of there.

And every time, I saw a spotless bottom of the tank. No buildup, no leftovers, nothing. It looked slick and shiny as if it were brand new.

Kellys travel trailer in the desert

Fear-Inducing Claims From Manufacturers

Therefore, it makes me wonder when I read different tank treatment manufacturer's claims that without using a biodegradable tank treatment, there will be all these problems. I have read you'll have 'a buildup and the solids will not disintegrate,' or 'bad bacteria will build up and cause odors,' or 'if you don't use this, you'll certainly get buildup/ a clog/ a poop pyramid.'

I read these statements and cringe a little. I have used NO treatments (Except for my 5-month stint in Florida, where the heat caused some smell.) and have had NO issues.

The Best Recreational Vehicle Toilet Hack Ever

THAT SAID, I also DO NOT put toilet paper down my RV toilet. This is the #1 cause of clogging. Still, without any tank treatment, I have had zero issues.

Toilet Paper Roll team over

My tank is always perfectly 'clean' after I dump. I look down into the black tank every time. There are no residual bits, nothing. I flush for 20 seconds or so, and there's nothing left in there that I can see, AND I have never had any issues.

Simple Solutions

My point is that I don't exactly believe in tank treatments.

Sure, they will help break down toilet paper, but there are ways around needing to. Just rip it up a little before using it, use septic-safe TP, or better yet, don't put it down your tank at all.

Follow these tips, and in my opinion, there is zero need to use a treatment unless using it to eliminate RV toilet stinks.

Kellys rig at roadside pulloff

Conclusion

A properly working black tank should never emit odors into the interior of recreational vehicles. (Except for extreme heat- this sometimes makes black tank smells so bad you do smell them inside.)

In the rare case that you do have odors, you must figure out what the problem is and then take the proper action to correct it.

It's not a fun job, but fixing a problematic RV black tank smell is something that should be taken care of immediately. Nobody wants to endure a camper sewage smell.

If you can't figure out why your RV smells like sewer yourself from the tips above, get some professional help at a service center.

I hope you don't have any problems with your black holding tank, but if you do, good luck with it!

Kelly Headshot

Hello! I'm the co-founder of Camp Addict, which my biz partner and I launched in 2017. I frigging love the RVing lifestyle but in December of 2020, we both converted to part-time RV life. Heck, I lived in my travel trailer for over 5.5 years, STRICTLY boondocking. I learned a lot about the RV life and lifestyle during those years. Now we share what we know with you here at Camp Addict.

After that many years of wonderful full-time travel, it was time for something new. These days, I'm often found working from my new Az home, and sometimes plotting and scheming whether or not to start collecting farm animals (or plotting my next RV trip!).

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