My RV Toilet Smells When I Flush

Key Points:

• Odors Come from the Black Tank – Smells rise through the toilet pipe when flushed, caused by anaerobic bacteria breaking down waste.
• Best Solution: Bacteria & Enzyme Treatments – Aerobic bacteria push out odor-causing bacteria while breaking down waste effectively.
• Chemical Treatments Can Make Things Worse – They kill all bacteria, stopping waste breakdown, increasing clogs, and are illegal in some states.
• Deodorizers Only Mask Odors – Strong fragrances don’t eliminate smells and often contain chemicals that disrupt waste breakdown.
• Hot Weather Intensifies Odors – Heat evaporates liquids, exposing solid waste and making smells linger longer.

No one enjoys walking into a bathroom right after someone has taken a big ol’ number two, but at least the smell can fade quickly. Now, imagine that same scenario in your RV—except the odor lingers for hours, days, or even longer. This is a common frustration for many RVers searching for a solution to persistent toilet smells, and probably the reason you’re here. In this article, we’ll explore the causes of these odors, effective ways to eliminate them, and tips for managing smells in high temperatures.

Why Your RV Toilet Smells When You Flush

The toilet is the gateway to the black tank in your RV. Every time you flush the toilet, there is a pathway for odors from the black tank to rise up through the toilet pipe. The reason for a stinky black tank is obviously the human waste that is put in there. Inside your stomach, anaerobic bacteria break down food as a part of digestion, expelling the materials the body doesn’t need in the form of solid waste and gas. This bacteria continues breaking down waste inside the black tank because they are expelled every time you poop. This means the odor creating bacteria are trapped in the black tank with all the waste, which is paradise for them because that’s what they need to thrive. 

The trick to getting rid of that smell is to add a type of bacteria that doesn’t create odors. Aerobic bacteria, when added in the right concentration, are like bouncers who push out the odor-making bacteria, eliminating tank odors.

Note: For more information on how both types of bacteria work in your holding tanks, refer to our guide on Why Bacteria and Enzymes Are Good for Your RV Holding Tanks.

By mentioning aerobic bacteria, we are shamelessly foreshadowing our recommendation for the best way to fix a stinky RV toilet. Lets review some methods used to fix odors that may exceed your expectations and others that are popular, but really aren't as effective as you might hope.

How to Fix a Toilet Odor Problem

There are several ways to fix an odor problem with your RV toilet, but not all of them are methods we would recommend. Some may seem like they are fixing the problem when they actually can make it worse.

Note: For more detailed information on getting rid of odors, refer to our Series on RV Toilet Odors.

Kill the Anaerobic Bacteria

Lots of tank treatments out there are nothing but strong chemicals that kill all the bacteria in the tank. Killing the stinky bacteria won’t stop smells because odor molecules will still be slowly released from the waste as it’s softened by the liquid in the tank, and there will be no bacteria to continue waste breakdown, so the risk of developing a clog goes up too. Chemical treatments or zinc/mineral products halt waste breakdown and are on the risky end of the scale (not to mention illegal to use in some states).

Cover The Smells With Strong Fragrances

Any time you see the term “RV Tank Deodorizer” or “RV Toilet Freshener,” be careful. Most deodorizers don't eliminate smells, they just mask them with more powerful fragrances that may smell better in theory but are usually so strong that they become just as annoying as the stinky smells. In addition to this underwhelming solution, most deodorizers include caustic chemicals that will kill the bacteria. So, not only are you adding an equally powerful smell, but you are also encouraging clogs by stopping the waste breakdown.

Use Bacteria and Enzyme Treatments

This is the best option and the one we recommend because these products eliminate odors, promote waste breakdown, and the risk if you are exposed to it is low; you can take care of potential odor issues and prevent clogs all with the same treatment. High-quality bacteria and enzyme treatments (like Unique RV Digest-It Ultra) add a blend of aerobic bacteria and enzymes that breaks down waste without producing odors. 

But make sure you choose a bacterial treatment that is high-quality and draws upon various bacteria strains to harness the most effective breakdown results. High-quality treatments include bacteria strains that are sourced with the greatest care and quality in mind, so the resulting product returns powerful results.

For the most comprehensive information on eliminating poop smells in your RV, read through our Series on RV Toilet Odors.

Why are Toilet Smells Worse in Hot Weather?

Hot weather primarily causes more pungent smells because heat causes liquid to evaporate much quicker, removing the odor barrier and exposing solid waste. Evaporation also causes the odor molecules to travel into the air with the evaporated water, allowing odors to linger much longer. Water is one of the most important elements to add to your holding tank when camping in hot weather. For more information on camping in hot weather and the importance of water in your holding tanks, refer to our guides on How to Control RV Holding Tank Smells in High Heat and Why Using Lots of Water in your RV Toilet and Holding Tanks is Crucial.

Review

Odors are never an invited guest on your RVing adventures, but our Series on RV Toilet Odors will help you avoid odors before they develop. Let’s briefly review what we covered in this article:

• Poop smells when you flush are rising up from your holding tank through the toilet pipe; if this is the case, you probably don’t have enough water covering the waste in your tank.
• There are several ways people try to zap toilet odors in their RV:
  • Use bacteria and enzyme treatments to get rid of stinky bacteria – this is the option we recommend because bacteria and enzyme treatments are approved for use in every state, and are much more effective at both waste breakdown and odor elimination.
  • Kill the bacteria with chemicals or mineral treatments – we do not recommend this option because certain chemical and mineral products are illegal in some states, can be dangerous to humans if exposed, and halts all waste breakdown, increasing the likelihood of clogs and additional odors.
  • Cover the poop smells with deodorizers – we do not recommend this option either as most RV toilet deodorizers contain harsh chemicals and end up adding their own strong fragrance that is typically no better.
• Poop smells are worse in hot weather because evaporation exposes solid waste and causes odor molecules to become airborne for longer. Ever wonder why farting in the shower smells way worse? This is why.

If you ever have any questions, or need help with your holding tanks, we have trained and certified RV technicians in-house for this exact reason! Please reach out if you have persistent problems or burning questions. In the 30 years we have spent helping RVers with their holding tanks, we see the same struggles time and time again. So if you are having trouble, odds are someone else has had it too, and odds are, we have helped them through it!