Learn How To Eliminate Holding Tank Odors This Summer!

My RV Toilet Smells When I Flush

June 11, 2020

My RV Toilet Smells When I Flush Image of RV Toilet Bowl With Gross Smells Coming From The Bowl


  • Your toilet smells because “bad” anaerobic bacteria from your stomach are breaking down the urine, toilet paper, and poop in the holding tank. In that process, they’re releasing hydrogen sulfide gas, which causes that all-too-familiar poop smell!
  • To eliminate this toilet odor, you need to stop the “bad” anaerobic bacteria from creating the hydrogen sulfide gas.
  • You don’t want to kill the bacteria inside your holding tank because without them, solid waste will collect, clog your tanks, and cause your sensors to read improperly. Instead, you want to replace the “bad” bacteria with “good” aerobic bacteria.
  • To do this effectively, you need to use a high-quality bacteria-based treatment. Not all treatments are created equal, so make sure you choose the best. We recommend Unique RV Digest-It.
  • Besides using the right bacteria-based treatment, you need to follow the proper tank-maintenance procedures. We recommend that you follow our proven, comprehensive guide: The Unique Method.

Nothing ruins an RV camping trip like nasty odors coming from your RV’s toilet! Whether your RV toilet smells when you hold down the flush pedal, or the smell entirely pervades your living space, awful odors in your RV can be frustrating, disgusting, embarrassing, and even dangerous. Luckily, there is an easy solution to controlling RV toilet odor. (More on that later!)

But first, what causes RV toilet odor? The nasty odors emanating from your holding tank are a result of “bad” anaerobic bacteria (from your stomach) breaking down the urine and solid waste — toilet paper and poop — inside your holding tank and releasing hydrogen sulfide gas (that horrible rotten egg smell). If these “bad” anaerobic bacteria aren’t controlled, you’ll be stuck dealing with awful odors.

Inside your stomach, anaerobic bacteria are essential in the process of breaking down food, acting as a crucial component of digestion. Their main objective is to break down solid food. Anaerobic bacteria thrive inside your digestive tract because they don’t require oxygen to survive. But this lack of oxygen is problematic, because it causes these bacteria to be unable to release oxygen as they break down the waste. Instead, they break down the waste and release hydrogen sulfide gas in the process. When you pass gas or burp, it’s normally from the over-production of gas from these anaerobic bacteria doing their jobs. They need to break down the waste, and the gas they release has to go somewhere.

When you use your RV’s bathroom, these anaerobic bacteria enter your holding tank and continue to break down solid waste. As mentioned above, this process emits hydrogen sulfide gas. When you flush your RV’s toilet, the valve slides open and momentarily allows all those foul-smelling gasses to seep into your RV. Also, if your tank’s seals are disintegrated, odors may leak up into your RV.

Now that you understand exactly why bad RV toilet smells occur, what are the solutions?

The best way to control RV toilet smells is to eliminate “bad” anaerobic bacteria. There are three basic options for doing this:

  1. Kill the anaerobic bacteria with caustic chemicals or formaldehyde
  2. Cover the smells with strong fragrances
  3. Replace “bad” anaerobic bacteria with “good” aerobic bacteria.


Killing The Anaerobic Bacteria

Let us be clear about this right off the bat: You never want to just kill the bacteria inside your holding tank with caustic chemicals or formaldehyde-based products. The bacteria in your tank are extremely crucial in the process of waste breakdown. If you kill them, it can and will lead to an excessive accumulation of solid waste in your black water tank. As a result, a pyramid plug will almost certainly develop. And beyond this, it becomes all the more likely that you will experience other clogs and disgusting odors in your toilet.

Besides being problematic inside the holding tank, we also recommend that you avoid formaldehyde products because they are simply not safe for people, pets, or the environment. This alone should give you pause the next time it’s recommended that you use an "old-school" chemical cleaner or formaldehyde product. They’re pretty much bad all round!

Covering The Toilet Smells With Fragrances

A close cousin to the old-school formaldehyde treatments are those that contain overpowering fragrances. These products simply cover one bad smell with another. If a product comes with an overpowering fragrance, you can automatically assume that product isn’t very good at truly eliminating odors or breaking down the waste at its core. It’s just a mask for the real problem!

Replacing The Bad Bacteria With Good Bacteria

The best way to solve toilet odors (without causing clogs and backups) is to replace the “bad” anaerobic bacteria with “good” aerobic bacteria.

If you’re like most RV owners who don’t want caustic chemicals inside the small living space of their RV, then this third option is honestly the only suitable option! 

And, as it turns out, it’s probably the easiest and definitely the most effective! To start off, treat your tank with a high-quality bacteria-enzyme product. We strongly recommend RV Digest-It. This product is the best RV holding tank treatment available today and comes in liquidscoopable powder and drop-in pod formulations. 

RV Digest-It works so well because it supplements your holding tank with “good” aerobic bacteria. Every treatment infuses your tank with literally billions of these “good” bacteria. Like we said above, instead of emitting smelly hydrogen sulfide gasses, aerobic bacteria release only carbon dioxide and water when breaking down waste, which leaves your holding tank odor free.

Again, not all bacteria treatments are created equal, so make sure you’re not throwing money down the drain by buying overpriced and underwhelming treatments. Most bacteria / enzyme treatments available today use old technology and watered-down formulations that will not solve your odor or waste problems. You can learn more about selecting the right treatment here.

Implementing the Right Habits

So we’ve established that  filling your holding tank with overpowering fragrances and killing the bacteria with chemicals isn't exactly the most effective way to rid yourself of RV toilet odors. Hopefully, you’re now convinced that a high-quality, bacteria-based holding tank treatment is the all-round best option! 

But there’s actually more to the equation. Even if you are using the best treatments like RV Digest-It, if you don’t implement the correct black water care habits, you may still experience problems.

Think of it this way: It won’t matter if you buy the best toothpaste and toothbrushes if you are constantly scrubbing your ears with them! It might seem obvious, but if you want something to work like it’s supposed to, you have to use it the way it was meant to be used. 

This is where proper black water care habits come in. To make sure you’re treating your holding tanks correctly, we recommend following The Unique Method, our comprehensive wastewater treatment guide we’ve developed from thousands of conversations with RVers all over the country.

Basic implementation of The Unique Method includes the following steps:

  1. Always keep your black tank valve closed, unless you’re dumping your tank.
  2. Always treat your holding tanks with a high-quality bacteria + enzyme treatment each time you dump. We suggest Unique RV Digest-It.
  3. Always fill your toilet bowl with water before you use the toilet. This will help waste to flow effectively down the line.
  4. Use ample amounts of water each time you flush your toilet. Water is a huge component of proper tank maintenance. We recommend holding down your flush pedal for ten full seconds each time you flush your toilet. This will hydrate the good bacteria inside the tank and allow them to adequately break down solid waste. It will also ensure that all of the solid waste inside your tank is covered by water, which will help suppress odors.
  5. Always keep several inches of water in your toilet bowl. This will prevent foul smells from seeping into your RV.
  6. Keep your tank temperatures below 85 degrees. If you believe the tank is exceeding 85 degrees, use more water with each flush and consider increasing the treatment dose.
  7. Ideally, you should dump your tanks every 3-5 days for optimum odor control. If you extend the time between dumps, treat your tanks every 4 days with your bacteria + enzyme treatment and keep plenty of water in your holding tank. Doing so will boost the microbial count inside your tank and allow the bacteria to work in this non-optimal environment.
  8. Flush your holding tank for 20-30 minutes every 3-5 dumps with a built-in tank-rinser, external tank-flusher, or wand. This is crucial, because waste (no matter how well it gets digested by your tank treatment) will collect and accumulate in the low spots of your holding tank if your RV isn’t parked 100% level (and most RVs are always parked ever so slightly out of level). In this case, waste cannot gravity-drain when you dump your tanks, so it must be manually flushed out.
  9. Never clean your toilets with chemicals or bleach. Use only RV toilet cleaners, like Unique RV Toilet Cleaner. Using chemicals or bleach will kill the active bacteria that are doing their part to keep your holding tank systems working properly.
  10. Perform a deep clean on your black tank twice per year. Unique Tank Cleaner is specially designed for biannual tank treatments. This will flush out the system, remove waste from the sidewalls and tank floor, remove debris that may have collected on the sensor probes, and lubricate your valves and seals.

We can’t overstate how crucial it is to use plenty of water in your holding tank. This hydrates the aerobic bacteria, helping to break down waste. Also, using plenty of water in your holding tank creates a barrier over the waste. This can drastically help to control those bad RV toilet odors. 

Don’t think it’s important to cover waste with water? Just step inside a porta-potty that contains a large mound of uncovered poop, and the stench will be unbearable. But if water covers the poop, the smell will not be so bad. The same thing applies to your holding tank! In addition to keeping plenty of water in your tank itself, we also recommended that you fill your toilet bowl with a few inches of water (just like your toilet at home), creating yet another barrier between you and those disgusting smells.

Why does my RV toilet smell in hot temperatures? And what can I do to remedy this?

These are great questions. It’s very true that hot temperatures can make RV toilet smells even worse. Here’s why: High heat allows the “bad” anaerobic bacteria to flourish instead of the “good” aerobic bacteria. So if you are experiencing odors in hot weather, you simply need to use more water in your holding tank. This will help the “good” aerobic bacteria from RV Digest-It to thrive. If the odor issue is especially persistent, we also recommend adding more RV Digest-It to increase the “good” bacteria in the tank.

To increase the amount of water inside your holding tanks, simply hold down your toilet flush pedal longer with each flush. It can also be helpful to dump your holding tank more often (every 4-5 days in hot weather).

Finally, in excessive heat, you may want to include a mineral/salt product like Unique Tank Odor Eliminator into your normal treatment regimen. This product is designed to eliminate tank odors in high heat situations, but it will not break down waste, so it should be used in conjunction with RV Digest-It, not in place of it. (Important note: We like to be completely transparent about all our products, and Unique Tank Odor Eliminator is no exception. With that being said, this product is especially unique, and using it may involve some minor risks. To find out more about Tank Odor Eliminator, please read our full transparency report!) 


Now that you have the tools to prevent disgusting RV toilet odors from ruining your adventures in the great outdoors, please feel free to read our additional articles. If you need more assistance, or have any further questions, please feel free to reach out to us at support@uniquemm.com. We’re here to help, always. 

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