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How to Control RV Holding Tank Smells in High Heat

  • 7 min read

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Article 4 of 4 in Series: RV Toilet Odors

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Key Points:

  • Odors are more potent in high heat because evaporation causes odor molecules to vaporize and linger in the air.
  • Evaporation of water in the black tank will expose solid waste and deprive the aerobic (good) bacteria of the water they need to survive and reach the waste.
  • There are several options for taking care of odor problems in high heat, and you’ll need to weigh your camping needs and the risk of using certain products to fix high heat odor issues. 

High heat can cause strong RV toilet odors to go from bad to worse in no time. Dealing with these odors is not only frustrating, it can easily ruin an RV trip. Thankfully there are solutions that allow you to camp in high heat locations without being flooded with those foul sewer smells. In this article, we’ll briefly review why odors are worse in high heat, and provide some simple solutions on ridding your toasty RV of odors. 

What Causes Odors to Increase in High Heat?

The reason for this is as simple as revisiting your high school science books. Like Newton’s third law (for every action there is an equal and opposite reaction), as heat rises in the holding tank, the water evaporates and is reduced. We all know heat causes water to evaporate, so if RV holding tank temperatures rise, water evaporates and begins to expose the solid waste to the air. When that happens, odors could have free reign in your RV. We recommend frequently checking that seals are strong, vents are working properly, and several inches of water is always kept in the toilet bowl because these are the primary areas where odors can slip by.

Aside from simple evaporation, heat actually provides more energy to odor-infused liquids to transform into vapors; basically, when liquid vaporizes, odor molecules become airborne and the humidity in the air from the evaporation causes them to linger longer and travel farther. Heat is something our bodies produce, meaning the odor-causing bacteria that comes from our poop was thriving inside our gut because the temperature of our intestines is a great environment for them. When they are deposited into a hot holding tank, it’s like they never left home and continue thriving, giving off their odors. As if all this wasn’t aggravating enough, heat also causes your nose’s odor receptors to be more sensitive, so as the temperature rises, you can actually smell odors more intensely.

For wise RVers who use bacteria and enzyme treatments in their tanks, know that high heat causes the good bacteria from the treatment to slow down and become less effective, just like humans do when we get overheated. But the stinky bacteria love heat because it gives them more energy to continue releasing smells. So really, heat helps the stinky bacteria thrive, and figuratively hamstrings the good bacteria, making it impossible for them to neutralize the odors from the bad bacteria.

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

Here’s a simple, condensed representation to help you remember the basics of maintaining odor-free tanks while camping in hot weather:

  • High heat + low water + stinky bacteria = increased odors
  • Moderate temperatures + plenty of water + odorless bacteria = odor-free RV

Knowing why heat causes odors to increase is great, but you want to know how to get rid of those odors when you’re adventuring in the hot outdoors.

How Do I Know When Holding Tank Temperatures Are Too High?

We knew this question would come up, so we conducted some brief testing of holding tank temperatures and found that when parked on concrete or asphalt, tank temperatures nearly match the outside ambient temperature but were 10 degrees cooler when parked on grass or dirt. This means simply attaching a thermometer on the outside of your RV will give you a pretty solid reference for what your tank temperatures might be; if it’s 95 degrees outside, that means it’s probably too hot in your holding tanks. It’s also important to note that while traveling on asphalt roads (especially at high speeds) the heat created from the vehicle or RV engine will pass under the RV and contribute to even higher tank temperatures, so be aware of this when moving your RV to a new location in high temperatures.

How to Control Odors in High Heat Environments

How you control odors increased by high heat heavily depends on your camping style and your willingness to use certain products. You have some different options when controlling odors in high heat camping situations, but not all of them will fit your situation well:

  • Use more water in your holding tanks to cool them down and cover the waste.
  • Add more bacteria and enzyme tank treatment (like Unique RV Digest-It Plus).
  • Dump more often.
  • Use a zinc-based product to control odors when water is limited (where legal)

Some of these options are what we recommend for every camping style, but we realize that sometimes the ideal solution doesn’t fit with your circumstance. The following sections will go into detail about why each of these options is good and why some of them may not be feasible for some campers.

Use More Water

A generous amount of water does three things in your holding tank:

  1. It keeps the good bacteria from a treatment like RV Digest-It Plus alive and effective.
  2. It keeps the tanks cool.
  3. It provides an odor barrier by keeping solid waste submerged.

As you’ll see in the next section, one of the primary ways to combat increased odors in high heat is to use a bacteria and enzyme tank treatment product. The bacteria in these products are called aerobic bacteria and they break down waste like the smelly kind does, but they don’t release odors. In fact, they actually push out the stinky bacteria so odors go away completely instead of being covered by flowery fragrances like some deodorizers do. But the good bacteria need water to survive, and water is also the pathway on which bacteria travel to reach the waste. If you allow too much water to evaporate, the bacteria will not be able to reach all the waste.

When tanks get too hot, adding more water will cool them down and give the good bacteria the jolt they need to thrive once again. Aerobic (good) bacteria respond to heat like humans do; when we get too hot, we move slowly and our energy is sapped quickly. Cooling down is what restores our energy, and the same is true of aerobic bacteria. When they are too hot, they slow down and do not attack waste as effectively. Adding water and even ice is the quickest, easiest way to start cooling down your tanks.

Water is also a natural odor barrier, which is why we encourage you to flush for 10 seconds after every bathroom trip and keep several inches of water in your toilet bowl. Even if you never used a tank treatment, using lots of water in your black tank will reduce the potential for odors simply because it blocks the odor molecules from rising. And keeping several inches in your toilet bowl at all times while parked is a secondary odor barrier in case evaporation in the tank happens faster than you expect.

Add More Bacteria and Enzyme Treatment

If you know you will be camping in a high heat environment, we recommend starting out your trip using a bacteria and enzyme tank treatment like Unique RV Digest-It Plus and having more on hand in case odors become a problem. The type of bacteria in RV Digest-It Plus and other products like it does more than break down solid waste without releasing odors; it actually pushes out the odor-causing bacteria that is already on the waste. Bacteria are efficient at breaking down waste, but the more there are, the more efficient they'll be, so if odors are becoming a problem in a high heat camping situation, add more bacteria and enzyme treatment. In addition to this, you may also want to add more water to ensure that the existing and added bacteria all have enough water and moderate temperatures to tamp down stinky odors.

Dump More Often

As much as we all hate dumping, that may be the best solution to an odor problem when camping in hot temperatures. Many campers who boondock in high heat areas are extremely conservative with their water usage precisely because they don’t want to fill their wastewater tanks too quickly or drain their freshwater tanks too soon. However, if you are dealing with severe odors in that situation, it’s unlikely that adding more bacteria and enzyme treatment will help because more water will probably not be added as well. There are some products out there that could provide a level of relief without adding much water, but we don’t recommend them in the interests of health. However, we want you to make your own decision about treating your tanks, so we are going to give you a brief look at those types of products in the next section.

Consider Zinc/Mineral-based Treatment Products (where permitted)

Zinc and mineral products will kill smelly bacteria, but in zinc-based products that also include enzymes, the waste will still be quickly broken down and the zinc takes care of any odors. We always recommend bacteria and enzyme treatments over zinc-based treatments because zinc is considered a nonbiodegradable toxic chemical according to the laws of some states and can cause serious damage to your skin, eyes, and lungs if exposed. So use it cautiously, and be sure to confirm that state laws do not prevent you from using this type of treatment.

In cases where frequent dumping is unlikely and water usage in tanks is limited, zinc and enzyme treatments will effectively take care of odors and waste breakdown, but even with this type of product, a certain amount of water is important; enzymes and the zinc itself use water as a pathway to break down waste or zap odors, so the more water in the tank, the more effectively odors will be suppressed (regardless of treatment type). 


Now that we’ve gone through in detail the options you have for controlling tank odors in high heat situations, you have all that you need to sweat to your heart’s content on your next trip without worrying about odors. But just in case you need a refresher, here’s a brief overview of what we covered in this article.

  • Odors increase in high heat because:
    • Heat causes evaporation, which leads to exposed solid waste, vaporized odor molecules that hang around too long, and ineffective aerobic bacteria.
    • Hotter temperatures cause the human nose’s odor receptors to be much more sensitive to smells.
  • Options for controlling odors in high heat situations include:
    • Using more water in holding tanks.
    • Increase the amount of bacteria and enzyme treatment in the tank.
    • Dump your holding tanks more frequently to reduce the amount of accumulated waste.
    • Consider using a zinc or mineral-based tank treatment to take care of an immediate odor problem (if permitted by the state where you are camping)

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