It can be difficult to determine exactly where disagreeable smells are emitted from while in a motorhome or travel trailer. This is especially true for newbie RV owners who are not fully familiar with their various RV systems.
One thing is for certain though, when an RV bathroom starts to smell, it smells bad, and in a space as small as an RV, most people want to rid themselves of those toilet odors as soon as possible.
So, today I want to educate my readers on how RV toilets function, the most common causes of bad odors in an RV bathroom, and some solutions for resolving those issues. Additionally, I’ll give some tips on preventative measures that can be taken to ensure you never have to endure the dreaded smelly RV toilet.
How RV toilets work
RV toilets function in a different manner than the vast majority of toilets found in American homes and businesses. There are a few different types of RV toilets on the market, but for the purposes of today’s topic, I’m going to focus on the common gravity flush RV toilet. As the name implies, these widely used toilets utilize gravity to dispose of solid and liquid waste in the toilet bowl.
Looking into a clean and unused gravity flush toilet, most people immediately notice how little water is in the bowl. This water is pooled on a small plastic or rubber flap that completely covers the output hole in the bottom of the bowl. When the RV toilet is flushed, the flap opens downward, allowing the pool of water and whatever else was in the bowl to drop into the black water tank below.
An RV black water tank, frequently referred to as the “black tank”, is a waste collection tank mounted on the bottom of an RV that exclusively holds RV sewage.
While flushing, water from the RV’s fresh water tank is released into the toilet, rinsing the inside of the bowl and keeping it fresh and odor-free. Many RV toilets flush via a pedal on the floor, while some use a switch that is pressed by hand.
The small pool of water that collects on the toilet flap serves two purposes. First, it aids in cleanly sweeping waste down into the collection tank. Secondly, it creates an airtight seal that prevents sewage gasses from the RV black tank from entering the RV. Without this small, sealing pool of water, RV bathrooms would perpetually smell.
Reasons why your RV toilet stinks
Alright, here’s the point in the article where we dive headfirst into why your RV toilet smells. Almost all RVers have run into at least one if not all of these issues at some point in their RVing career.
So, don’t get down on yourself if you realize you’ve been skipping out on a bit of important RV maintenance. It’s easy to forget about and doesn’t mean you are a gross person.
What can I say, sh!t happens!
RV vent fan is turned on
Well, starting with the simplest possibility first, RV ventilation fans have the ability to pull sewer gasses from inside of the black tank, into an RV. This occurs when a vent fan in the RV is turned on, and a person using the toilet flushes. In the second or two that the toilet flap is open while flushing, the vent fan pulls smelly gas from the waste tank into the RV.
Surprisingly, the vent fan doesn’t even need to be in the bathroom to cause this. Any vent fan in an RV has the ability to cause this unfortunate issue. So, if you consistently find that your RV toilet smells when flushed, you might be leaving too many vent fans on while you do your business.
What to do
To check if this is causing your RV toilet odors, you’ll need to perform a simple smell test.
Start this smell test by turning on the vent fans that you normally have on while using the restroom. Enter your RV bathroom and (without relieving yourself first) put your face down near the toilet bowl. Flush the toilet and cautiously inhale through your nose.
If your RV vent fans are pulling sewer odor into your RV, you’ll most likely be blasted in the face with the smell of your own waste. Gross, but necessary.
The solution? Turn off all RV fans before using the toilet.
RV toilet is dirty
Okay, I stand corrected, this has got to be the most simple cause of RV toilet odor.
Surprise, surprise, toilets get dirty. This is especially true when the toilet is frequently used by men who stand while urinating. Standing to pee is not clean or hygienic, and results in a whole lot of urine splattering onto the floor, walls, and toilet. That’s the truth of the matter.
But let’s be honest, it doesn’t matter if you sit, squat, or stand, everyone makes a mess in the bathroom. If you don’t stay on top of cleaning your bathroom and toilet, it will eventually start to smell.
What to do
Clean your bathroom!
And clean it well. I’m always shocked at how deep some of the contours of a toilet can be. Get into the hard-to-reach corners with powerful cleaning agents and some pleasantly scented soaps.
Sniff around for smelly areas. If your RV has seen some days, it might be time to replace some of the bathroom trim or wall paneling, as they may have become infused with yucky bathroom gunk.
If a fully clean bathroom does not rid you of your RV toilet odor, you can move on knowing that the cause lies elsewhere.
Leaky toilet flange
Do you remember that flap I described earlier? The one that covers the toilet bowl hole, and, with the aid of a small pool of water, keeps sewer smell from entering your RV?
Well, that little flap-sometimes called the toilet flange seal-can becomes misaligned, warped, or cracked over years of use. When it fails, it fails to hold the important pool of water up, resulting in a gap that black tank gas can potentially escape.
What to do
This issue is easy to diagnose, and not too hard to fix.
If you consistently find that your toilet bowl is dry of any water, despite the little water pool refilling after you flushed last, then the flap is almost certainly not sealing and should be realigned or replaced.
If you feel confident in your DIY capabilities, this project should be fairly easy to complete with a few hand tools and a replacement part. If you are not as confident in making RV plumbing repairs, a local RV technician will be happy to help you out.
Blocked vent pipe
All RV black tanks have a ventilation pipe that travels from the black tank itself, through the floor and walls, and out the roof of the RV. This vent pipe allows noxious, and potentially harmful gasses to safely vent out of the black tank and the RV. Vent pipes terminate on the roof of an RV so that the gasses can safely disperse above people’s heads.
Occasionally, a black tank vent pipe can become blocked or clogged in some way. In extreme and rare circumstances, the blockage is caused by human waste in the black tank itself (gross!). Typically though, the clog is an accumulation of natural plant debris that has worked its way into the top of the vent pipe.
Another cause of a blocked black tank vent pipe can be from nesting critters or bugs such as mice, squirrels, or bees.
What to do
Checking if your vent pipe is clogged is quite easy if you have access to a hose and running water. With care, climb on to the RV roof. Have another person hand you the end of a water hose and feed it down into the top of the black tank ventilation pipe. Instruct your helper to turn the water on and watch the top of the pipe.
If it quickly overflows, then you almost definitely have a clog that will need to be cleared and cleaned. If it doesn’t overflow within a minute or two, or if you can hear the water splashing into the black tank, the vent pipe is clear.
Note: Very seldom do RV vent pipes actually become clogged. A person can spend years traveling in an RV without ever encountering this issue.
Clogged or overfull black tank
An RV’s black tank is a shockingly delicate environment. Black tanks require frequent maintenance, must be thoroughly cleaned several times a year, and, if neglected, can become quite disgusting.
That brings us to my least favorite RV topic to write about: the “pyramid of poo”.
A pyramid-shaped pile of solid waste can build up in a camper’s waste tank if the RV owner does not fill the tank with a sufficient amount of water, or if the tank has a leak. Without enough liquid in the tank, solid waste builds up until it clogs the toilet hole.
This can cause a myriad of issues, from the inability to properly flush, to faulty tank level sensors.
The primary cause of black tank clogs is people using too much toilet paper, and not using toilet paper made for use in a camper. RV toilet paper is safe for use in RVs and residential septic systems. When searching for RV toilet paper in a store, look for a label that says, “septic safe toilet paper”.
What to do
Over the years, RVers have discovered many clever ways to bust up a black tank clog. Some are quite involved, messy, and extraordinarily effective, while others are simpler but might take a few repetitions to do the job.
My favorite method is on the simple side of the equation. Using a stick, or flexible tube, do your best to bust a hole through the pile of waste. Make a hole that is big enough to allow you to fill your black tank with water via the toilet hole.
Fill your clogged tank approximately 1/3 full of water and then drive your camper around for 5 or so minutes. Aim to make turns that will intentionally slosh around the contents of the black tank and bust up the pyramid. Next, dump the black tank at a proper RV dump station. If the clog has not fully broken up, repeat the process until your black tank is fully clear.
How to prevent RV toilet stink
It is easy to avoid RV toilet smells by staying on top of toilet and tank maintenance. If you perform the following tasks consistently, you should have no problem keeping your RV toilet from smelling:
- Clean your RV toilet and bathroom
- Maintain a healthy black tank environment
- Dump black and gray tanks regularly
- Use septic safe toilet paper
- Clean and winterize your black tank before extended period of disuse
Frequently Asked Questions
Take a peek at what our readers want to know about RV plumbing systems.
What is a gray tank?
An RV gray tank is a waste collection tank similar to a black tank. Gray tanks collect used liquids and store them to be dumped later. RV showers and sinks drain into the gray tank. They are not meant to collect or store solid waste.
Can hot weather make my black tank smell worse?
Yes, hot weather tends to make RV sewage systems smell worse than normal. In extreme heat, bacteria in the black tank go into overdrive and produce higher-than-average levels of waste gas.
Fear not, your RV will not always smell like a toilet.
Give your rig’s plumbing system the inspections described above, and I’m sure you will be able to suss out the source of any smells. If, despite your best efforts, your RV toilet continues to smell foul, then it’s probably time to take it into the shop.
An RV technician will be able to find the source of the smell and repair it. Try not to be embarrassed about bringing your rig in for a stinky reason. Trust me when I say that your local RV tech has smelled worse.