Key Points:

• Your toilet smells because anaerobic bacteria from your gut produce odors while they break down the waste.
• Odors smell more prominent when the toilet is flushed because the odors are able to travel up the toilet pipe from the black tank.
• There are many products out there that can help you deal with odors, but some are more effective at eliminating odors than others.
• Odors will worsen and waste breakdown will stall in hot weather if you're not using enough water in your holding tanks to cover the solid waste.

It's never fun to walk into a bathroom right after someone else has dropped a number two, but the smell usually dissipates pretty quickly. What if that same scenario cropped up in your RV but the smell stuck around for hours, days, or even years? This scenario has been reality for many RVers desperate for a solution to stinky RV toilets. In this article, we will briefly discuss what causes toilet odors, some resources for fixing them, and some additional recommendations for controlling odors 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 (bad) bacteria break down food as a part of digestion, expelling the materials the body doesn’t need in the form of solid waste. This bacteria continues breaking it down inside the black tank because they are expelled along with the waste every time you poop. This means the stinky bacteria are trapped in the black tank with all the waste, which is paradise for them because that’s what they feed on. The trick to getting rid of that smell is to add bacteria that doesn’t create smells. Aerobic (good) bacteria are like bouncers who push out the trouble-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 (good) bacteria, we are shamelessly foreshadowing our recommendation for the best way to fix a stinky RV toilet. In the next section we'll review some methods used to fix odors that really aren't as effective as you might hope and others that may exceed your expectations.

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 with caustic chemicals

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 to push out odor-producing bacteria

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 Plus) 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:
  • 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.
  • 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.
• Poop smells are worse in hot weather because evaporation exposes solid waste and causes odor molecules to become airborne for longer.