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Article 3 of 4 in Series: RV Toilet Odors

Read series from the beginning

Key Points:

• Toilet smells are really coming from your wastewater holding tanks; aerobic bacteria are the best all-around odor-fighting organisms to have in your tanks
• Odors can become a problem when you’re not using enough water in your holding tanks, your tanks are too hot, you’re using counter-productive treatment products, or your ventilation system is not working properly
• Consider the type of care habits and treatment products you are using; some products help eliminate odors effectively and others do little good or add their own overwhelming odors

“How do I get rid of odors coming from my RV toilet? I never have this problem at home.” Plenty of RVers (even seasoned pros) have struggled with this question, and because the issue of RV toilet odors is so prevalent, it's easy to give up and assume that there is no workable solution. So know that this is a common problem and you’re not alone; whether you’re new or experienced, toilet odor problems can happen to anyone.

There are many “solutions” offered by fellow campers, online forums, RV service technicians, and websites that claim they will eliminate RV toilet odors, but we know from talking to thousands of RVers that these solutions provide very little odor-zapping power. We want to help you unpack the misconceptions out there about RV toilet odors and the most effective ways to combat them. The tips and care practices in this guide will show you how to eliminate RV toilet odors, so don’t let anyone (even yourself) tell you that you just have to live with a stinky RV.

Why Your Toilet Stinks

Let's clear up a slight confusion: almost every time you've experienced RV toilet odors, it's coming from the wastewater holding tank(s), not the toilet itself. After all, that is what the holding tanks are for: holding liquid and solid waste until you dump it. We all know what a strong smell can linger after we use the bathroom, but in an RV it can be worse because it's not being flushed away into an underground septic or city wastewater system; it's being moved from the toilet bowl to a tank under the RV floor. Until you're able to dump it, odors can always be a potential problem. Ideally, solid waste will be nearly liquefied while sitting in the tank because when you dump the tank, waste flows out using gravity; if the waste is too solid, it cannot flow out. The only way waste becomes nearly liquefied is because of the presence of lots of water and a healthy presence of bacteria and enzymes. Bacteria are like the scavengers of the microscopic world and break solid waste into its smallest possible size. So bacteria and enzymes are a very good thing in your tanks because they reduce the size of the waste.

Okay, but what's making the smell? Bacteria is the reason for the smell, so if you’ve read any of our other articles, you might wonder why we constantly encourage you to have bacteria in your holding tanks. Not all types of bacteria produce smells. In fact, the smell is caused by the anaerobic (bad) bacteria that resides in your stomach. Whenever you use the bathroom, some of that bacteria comes out with the waste and it continues releasing odors even while in your RV's holding tank. The solution to pesky odors is not to kill the smelly bacteria, but to replace it with bacteria that does not cause odors: aerobic bacteria. Each of these bacteria types perform the same function in different ways.

• Aerobic bacteria (odor-free bacteria) must have oxygen-rich, water-filled environments, emitting only carbon dioxide and water as they break down human waste and toilet paper.
• Anaerobic bacteria (odor-causing bacteria) don’t need oxygen or water to survive or thrive and release smelly hydrogen sulfide gas (the poop smell) as they break down waste.

Both of these types of bacteria will break down solid waste, which is an important process to control odors, but aerobic (good) bacteria is the one you want working en force. Aerobic bacteria make it into your tank(s) when you add it by way of bacteria-based tank products (like Unique RV Digest-It Plus). Both types of bacteria will eat solid waste inside the tank(s), but only the aerobic bacteria can consume waste without creating unwelcome odors. In fact, they overtake the smelly bacteria, which means they actually eliminate odors. Knowing how bacteria contribute to waste breakdown in your holding tanks, you should also know that the type of cleaning products you use on your toilet, your dishes, and other areas where it will end up in the tanks can either destroy or boost the efficiency of the bacteria’s waste breakdown process.

Guide: Why Are Bacteria and Enzymes Good for Your RV Holding Tanks?

There is always the chance that toilet smells are coming from a toilet bowl that is dirty; in this case, clean the toilet bowl. But if cleaning the toilet bowl doesn’t reduce the smell, it’s probably your tank, not your toilet bowl. While a dirty toilet bowl is usually not the culprit in this situation, it’s still a good habit to clean your toilet bowl regularly.

How to Keep RV Toilets from Smelling

Now that you know that anaerobic (bad) bacteria is the source of RV toilet smells, we can cover some of the common reasons for odor problems to arise. The fact is, even if you are treating your tank with a good bacteria and enzyme product, you might still experience toilet odor issues, sometimes not related to your care habits or treatment choices.

With this in mind, we’ve compiled a list of some common toilet odor issues RVers experience and our recommendations for solving them. These issues can be persistent and in some cases seem unsolvable, but most of the time, using the right products and following The Unique Method will do the trick; however, if you are dealing with an especially persistent problem, please reach out to our customer support team.

The primary reasons for RV toilet smells boil down to four things:

1. Not enough water in your RV holding tanks
2. Tank temperatures outside of the ideal range
3. Bad tank treatment or cleaning products
4. Ventilation issues

Not Enough Water

Water is an essential part of a healthy, non-smelly RV holding tank. We go through several water-related issues that can cause smells to develop and worsen over the course of a trip:

1. The poop in the black holding tank(s) is not covered by water
2. Your toilet bowl should always have water in it (unless driving)
3. The odor-free bacteria can’t survive and thrive
4. High heat is causing water evaporation or adverse environments for aerobic bacteria

1. The poop in the black holding tank(s) is not covered by water

Make sure the solid waste inside your black holding tank(s) is completely covered by water. If you’ve ever used a Porta Potty (and most of us have) then you know what we’re talking about. A Porta Potty that smells like death probably has poop stacking above the waterline, but one that has water covering the waste doesn’t smell so bad. The water acts as a barrier to the sewage odor, and the same thing applies to your holding tanks. The best, most convenient way to always have enough water in your black holding tank(s) is to hold the flush mechanism down for at least 10 seconds every time you use the toilet.

Guide: Why Using Lots of Water in your RV Toilet and Tanks is Crucial

2. Your toilet bowl should always have water in it (unless driving)

Your holding tanks aren’t the only thing that needs a healthy supply of water; you need to keep a moderate amount of water in your toilet bowl itself and refill it after every use, which adds yet another layer of odor control. You can add water to your toilet bowl by either partially holding down your flush pedal until the bowl fills or by applying the “fill” option on your toilet if your RV is equipped with this feature. 

3. The odor-free bacteria can’t survive and thrive

Use products containing good, aerobic bacteria (like Unique RV Digest-It Plus) in conjunction with ample amounts of water to push out the stinky, anaerobic bacteria. Aerobic (good) bacteria must have ample amounts of water to survive and reach the waste; if your flushing habits do not include allowing a lot of water into the tanks, the bacteria may not be working at their highest potential. The easiest way to ensure enough water in the holding tank is to hold down the flush pedal for 10 seconds every time you flush. By adding good bacteria and ensuring generous amounts of water in the tank(s), the waste will still break down, but you won’t have to deal with the smell! 

4. High heat is causing water evaporation or adverse environments for aerobic bacteria

Because excessive temperatures can cause water to evaporate from your toilet bowl and/or your holding tank(s), it becomes doubly important to use plenty of water. Water can evaporate at any temperature above freezing, but the higher the temperature, the faster water evaporates. After conducting brief tests, we found that you can simply take a temperature reading of the outside air to estimate the temperature of your holding tanks. This means if your own body is slowing down and getting tired because of the heat outside, the good bacteria in your tanks probably are too. In high temperatures, rapid evaporation will quickly lead to exposing solid waste above the water line and diminishing the vigor of the good bacteria. So if you know you will be camping in a place where temperatures get consistently high (above 85 degrees), it’s good practice to add more water to your black holding tank(s) than you normally would. Honestly, you can never use too much water (until you need to dump the tanks, of course). The more water you use, the less odors you will experience!

Guide: How to Control RV Holding Tank Smells in High Heat

Hot or Cold Holding Tanks

As we began to touch on in the previous paragraph, hot weather is something that can severely limit the effectiveness of the aerobic bacteria and increase odors. It's the perfect breeding ground for incredibly potent sewage smells. There are several reasons why hot weather makes smells worse:

1. Water evaporation: hot weather causes water inside the tank(s) to evaporate, exposing solid waste to the air, which increases smells; water covering waste is the best odor suppressor.
2. Energy reduction: aerobic bacteria are living organisms just like us, so when temperatures rise, their energy is sapped and they cannot break down waste and toilet paper as well, which will lead to odors.
3. Too much waste accumulated: obviously, the more waste that’s collected in your tank(s), the higher the potential for increased odors, especially in hot weather when evaporation can quickly expose waste in a very full tank; dump more often to stop these issues before they start.
4. Not using the right products and habits: we can’t say it enough...use The Unique Method as your regular tank care process; most problems can be avoided (even in hot weather) by stubbornly sticking to The Unique Method’s guidelines.

Couple heat with poop smells and you’ve really got a recipe for misery on your trip. We have an entire guide dedicated to why RV toilet smells are worse in high heat and how to get rid of them. Read about it in our next article on How to Control RV Holding Tank Smells in High Heat.

If you're camping in extreme cold, you'll likely experience similar problems with bacteria activity. When bacteria get too cold, they will start to work less effectively. Freezing sewage can also pose a problem since liquid expands when it freezes; a very full tank could crack or become warped during the freezing process. We recommend that you explore tank insulation options like wrapping your tank with insulated materials or using a tank heater. 

Guide: How to Keep Your RV Holding Tanks From Freezing 

Bad Treatment Products

The type of treatment and/or cleaning product you use can affect how much waste breakdown is happening in your RV holding tanks, which in turn affects the likelihood of increased odors. We walk you through several product-related reasons why smells are occurring:

1. Counter-productive tank treatments
2. Cleaning products that are neutralizing your bacteria-based tank treatment
3. Strong perfumes from your toilet odor solution

1. You’re using counter-productive tank treatments

Always use a high-quality product that will effectively break down waste and control RV toilet odors. The best product to accomplish this is a bacteria and enzyme blend (like Unique RV Digest-It Plus). A bacteria and enzyme blend will replace smelly, anaerobic bacteria with odorless aerobic bacteria that will both break down waste and eliminate odors. Enzyme-only treatments can help with waste breakdown, but enzymes alone cannot eliminate odors because all they do is break apart waste into smaller pieces; this solution may work for a short weekend camping trip, but extended trips may require different treatments.

Many chemical treatments kill bacteria as a by-product of covering the odor with a more powerful, but equally unpleasant smell and will also stop or severely limit waste breakdown, which can lead to clogs, sensor misreadings, and plenty of odors. These chemical treatments often include minerals (like zinc, bleach, and other substances considered toxic by some states) that could damage tank sensors, erode rubber seals, and can also negatively affect the environment and the human body. Some people employ varying homemade remedies, but our conversations with RVers have shown us that these homemade treatments often include chemicals, promise a lot but deliver very little, and should simply be avoided.

2. You’re using cleaning products that are neutralizing your bacteria-based tank treatment

If you’re using high-quality bacteria and enzyme tank products like Unique RV Digest-It Plus, sending chemical toilet cleaners and antibacterial dish soap down the drains will kill the tank-dwelling bacteria and negate their breakdown power (not to mention a waste of money). Use a bacteria-enhancing toilet bowl cleaner (like Unique RV Toilet Cleaner + Holding Tank Enhancer) instead of a bacteria-killing cleaner. We recommend using a bacteria and enzyme treatment in your gray/galley tanks as well, so if you decide to do this, it is also important to use non-bacteria killing soap (like Dawn Ultra) to clean your dishes and wash your hands.

Guide: What to Allow in Your RV Holding Tanks

3. You’re smelling the strong perfumes from your toilet odor solution

Be warned; many deodorizing treatments out there are just stronger, “less pungent” smells than the stinky poop odors you’re trying to remove. They often operate like a Glade aerosol spray or Febreze freshener spray does in a bathroom; it just fills the air with a smell that’s not as rancid as the bad smell but still makes your head swim. By using toilet odor control treatments that only mask odors, you’re putting a band-aid on the problem and potentially creating another if the deodorizing treatment contains bacteria-killing chemicals (and many of them do), which is the last thing you want to put into your bacteria-rich tank environment.

Improper Ventilation

Ventilation issues are the last thing most people think about when smelling odors, instead thinking there’s a problem with the tank or toilet. However, ventilation is a huge piece of keeping poop odors where they belong: far away from your sniffer. Some of the ventilation reasons for smells might surprise you:

1. Your RV is parked in a way that prevents sewer odors from properly venting
2. Vents weren’t installed correctly
3. Vents are clogged with debris
4. Leaks and broken seals can slowly release odors
5. Sewer gas is backing up into your RV through your black tanks (for hook-up campers)
6. Gray tank odors are backing up into your RV

1. Your RV is parked in a way that prevents sewer odors from properly venting 

If you position your RV a certain way, the wind will be able to blow vented odors back inside rather than allowing them to disperse into the outside air. For instance, some RVs have vents on the side, so you will want to make sure that side is facing the direction the wind is blowing. For other RVs where the vent is located on the roof, cyclone sewer vents can be attached to the top of the vent pipe. These vent supplements act like weather vanes, following the wind and creating a vortex that pulls odors up and away from your RV. 

2. Vents weren’t installed correctly

It may seem unlikely, but have your ventilation system inspected to ensure it was properly installed. Sometimes the hole in the ceiling of your RV where the vent would go was mistakenly never cut, which means none of the toilet odors can escape. Proper inspection and repair of your ventilation system can help to fix this issue.  

3. Vents are clogged with debris

Whether your vent is on the top of the RV or the side, debris can still collect inside, making it harder for odors to escape. If you are certain your vents were installed correctly and your RV is parked in a way that should allow odors to dissipate, you may need to check the inside of the vents. In high wind situations or simply over time, leaves, organic debris, and even living things can get stuck inside the vents. It’s good practice to check that all your vents are clear of debris as regularly as possible and certainly for seasonal campers, at the start and end of the season.

4. Leaks and broken seals can slowly release odors

Check your system regularly for damage to seals. Your tank ventilation system should be sealed completely from the inside living space of your RV, so if you are experiencing persistent odors despite adding water and more tank treatment, you may have some leaks or broken/fatigued seals. And this is no time to just add some deodorizing pods and move on, because if your ventilation system is compromised, it can cause damage to the tanks or eventually engulf the living space with overwhelming odors. So it’s important to inspect your seals regularly. The good news is that when you use Unique Camping + Marine products to treat your tanks, it helps soften the seals, extending their functional life.

5. Sewer gas is backing up into your RV through your black tanks (for hook-up campers)

Keep your black tank valve closed even while on hook-ups. If you’re following The Unique Method (and you should be), you’ll know that keeping your black tank valve closed is the cardinal rule of black tank care. Unless you’re dumping a full tank, your black tank valve should always stay closed. Otherwise, all the liquid will continually flow out of your tank, and you will be left with an exposed pile of stinking poop (which can develop into a pyramid plug) that cannot be efficiently digested by the odorless bacteria that needs water covering the waste. An open black valve even on hook-ups means that there is no barrier to stop gasses from the sewer hook-up from wafting backward into the tank and eventually the living space. Not only are these offensively smelly, but high levels can be hazardous because they contain methane.

6. Gray tank odors are backing up into your RV

For hook-up campers who keep their gray tank valve open, put a p-trap in the discharge hose to prevent sewer gas from backing up into your RV and deep clean your gray/galley tank(s) regularly. While you might think odors wafting from the hook-up line through the gray/galley tank would smell like sewage, many RVers have reported it’s more like a pungent garlic smell, which isn't much better than a poop smell; a p-trap uses water to block those odors from ever entering your gray tank(s).

For dry campers (boondockers) who have to keep their gray tank valve closed, odors can back up into your RV from accumulation of grease and soap scum waste inside your gray or galley tank. This is due to the residue not only from food grease, but also from soap, shampoo, conditioner, and even human hair that gets into the tank. It’s also important to make sure no solid food waste goes down the drain; always wipe your dinner plates before washing them and/or use a drain strainer to catch large chunks of food that could otherwise end up in your gray tank(s). Aside from good camping habits, you also need to treat your gray/galley tank(s) regularly with bacteria and enzyme treatments like RV Digest-It and deep clean them regularly with Dawn Ultra dish soap.

Guide: Deep Cleaning RV Wastewater Holding Tanks

Other Common Problems

1. Residual waste buildup inside your wastewater tank

Waste buildup can happen for a variety of reasons, many of which we’ve already covered: leaving your black tank valve open, lack of water in the tank(s), and using chemical treatments instead of high-quality bacteria and enzyme products. Additionally, if you’re not flushing/rinsing your tanks regularly (at least every 3-5 dumps), waste can hide in corners and crevices and start to fester. If your RV does not have a built-in rinser, you can use a backflusher or rinsing wand. It might seem like leaving a little bit of waste in your black tank(s) isn’t a huge issue, but letting a tiny piece of food rot in your refrigerator for years will stink just as much as a larger piece of rotten food. The same applies to your holding tanks. Even a tiny amount of residual waste can cause odors you’d think would only come from larger pieces, so it is crucial to regularly flush it out.

Guide: How to Flush Your RV Holding Tank

Guide: RV Holding Tank Shapes - Could Yours Cause Waste Buildup?

2. Stationary units accumulate residual waste in holding tanks because they’re out-of-level

This is another reason you should perform regular, long rinses on your holding tank(s); waste can accumulate in the low points of an out-of-level holding tank. Many people who live in RVs for extended periods of time will have issues with residual waste buildup. Your holding tanks use gravity to drain, but no matter how level you think your holding tank is, there is almost always a low point where waste can slowly build up until there is a block of poop stuck inside your tank, which can cause odors and clogs. Regular (typically biannual) use of a good bacteria-based deep-cleaner (like Unique Clean-It) along with regular, long rinses of your tank(s) should fix and prevent this sneaky problem. Rinse your tanks by using a built-in tank flush system, rinsing wand, or backflusher, or just fill your tank with fresh water and dump the tank several times.

Guide: Deep Cleaning RV Wastewater Holding Tanks

Evaluate the Care Habits and Treatments You Are Using

Proper RV wastewater tank maintenance is a 50/50 approach: 50 percent in the type of products you use and 50 percent in the care habits you practice. You need the best of both to achieve the aromatic bliss you desire in your RV. Adding a single bottle of treatment to the tank and walking away will just temporarily provide false peace of mind. If you're not pairing high-quality tank treatments with regular, healthy cleaning habits, problems will continue to emerge at the most inopportune times. Your goal is to control toilet odors and promote waste breakdown, but not every treatment product will deliver the all-encompassing results you are searching for.

Many of the top name brands or homemade treatment solutions tend to address only one problem like odors instead of controlling everything in one treatment (odors, waste breakdown, keeping sensors clear of debris, non-corrosive to tanks and seals, approved for use in all states, etc.). Waste breakdown and odor control are actually connected because nearly liquefied waste is always less smelly than piled up waste. But how exactly do you get waste to liquefy? The type of treatment product you use will either end waste breakdown or boost it, so be informed about the product you use in order to get the most effective waste breakdown happening in your tanks.

The primary product types used to treat RV holding tanks include:

• Bacteria and enzyme treatments (highly recommended)
• Enzyme-only treatments (recommended for certain camping styles)
• Chemical-based treatments (not recommended)
• Zinc and enzyme treatments (not recommended but effective for certain camping styles)
• Fragrance only treatments (not recommended as they often contain harsh chemicals)

We go through these treatment products in detail in The Unique Method. Get all the information you need to help you find the best product for your camping style by examining all the product choices.

Review

RV toilet odors are easy to avoid when you use high-quality treatment products and employ the right care habits. We’ve gone through a lot of detail in this guide, but the basic idea boils down to this:

• Use plenty of water in your wastewater holding tanks.
• Treat your wastewater tanks with high-quality, bacteria and enzyme products.
• Keep your tanks cool in hot weather.
• Ensure proper ventilation.
• Rinse your tanks often (every 3-5 dumps or after each trip).
• Follow The Unique Method consistently.

Now that you’ve had a very thorough walk through all the reasons why odors might be a problem in your RV, the next article will explore more deeply why smells become so much worse in hot weather.

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