15 Most Frequently Asked Questions About Composting Toilets

ShopTinyHouses has been in the Tiny Living world for a very long time. We've matched thousands of people with the toilet of their dreams... ok, that's ridiculous... but we actually have sold thousands of composting toilets to every type of user imaginable (even one guy who bought the toilet for his private island). 

To this point we've answered hundreds of unique questions around composting toilets. These range from the standard "what is a composting toilet?" to the honest, but awkward "what if I have diarrhea?" and also the the super strange "can my cat use my composting toilet?" 

We took some time to compile the most common questions (and added a couple of the bonus "strange ones"). If you have a question you think should be on this list, please reach out and let us know! Even if we don't include it here, we will absolutely respond back with an answer.

So, to borrow a phrase from 1990s Radio Shack, "you've got [toilet] questions, we've got answers." (...please don't sue us, Radio Shack). Let's dive in. 

1. What Is a Composting Toilet?

A composting toilet is a type of toilet that uses natural processes to break down human waste into compost, which can then be used as a fertilizer for plants (don't use it as fertilizer for your vegetable garden, though).

Unlike a traditional toilet, composting toilets typically separate urine and solid waste into different compartments to help the composting process. Some models use electricity or ventilation to help speed up the composting process, while others rely solely on natural bacteria and airflow. Composting toilets are often used in areas without access to sewer systems, as well as in eco-friendly homes and buildings seeking to reduce their environmental impact. Plus, they're a lot easier than a septic tank and cost thousands less.

2. Do Composting Toilets Smell? Will it smell up RVs and campers or my tiny home?

Composting toilets are designed to minimize or eliminate odors through proper ventilation and aerobic decomposition of solid waste. If used correctly and maintained properly, they should not emit unpleasant smells. However, if the toilet is not well-maintained or used improperly, there can be odors emanating from it.

It's essential to keep the toilet clean, emptied, and maintained following the manufacturer's instructions to prevent smells. Regular cleaning and adding composting material as needed can keep any odor under control. 

3. How Does a Composting Toilet Work? What Are the Two Main Types of Composting Toilets?

As mentioned earlier, composting toilets separate liquid and solid waste and do not use water as a flushing mechanism. Some split the urine and solid waste before they mix (like with self-contained, urine-diverting toilet), while others do the work inside the storage container before evaporation occurs (like with split-system models). These are the two main types of composting toilets and both have their pros and cons.

The solids hanging out in your toilet tank break down thanks to aerobic bacteria. To balance out the carbon-to-nitrogen ratio needed for top-notch composting, you will use some compost mediums - options include peat moss, sawdust, and the our favorite - "coco coir." This process even kills off any nasties you would normally find in human waste, transforming it into a nutrient-rich compost perfect for sprucing up your landscaping. Just don't go tossing it in your veggie patch, according to both compost toilet manufacturers and those sticklers you invite over for dinner parties.

4. How Do I Empty the Composting Toilet?

Don't let the thought of maintaining a composting toilet scare you, it's not as gross as it seems! The upkeep is minimal, with only occasional emptying required. You don't even need any fancy tools or skills to handle the job. And if you've ever had the joy of emptying a black tank on an RV or boat, you'll appreciate how easy composting toilets are to manage.

Our recommended toilets have convenient composting systems and process for speedy disposal. Say goodbye to the hassles of septic systems and water hookups! Composting toilets really are not hard to maintain - no water, chemicals, or plumbing needed.

Some units have a removable solids chamber that you can dump directly into a trash bag, compost bin, or take to your compost pile if composting is complete. Others use internal bags that can be removed and tossed either in the trash (Dry Flush) or into your compost pile (Separett). Since these toilets are each a little different, you can decide which emptying process you prefer. 


Can my cat use my composting toilet?

Super weird. We couldn't tell if she meant "put the cat waste into the composting toilet" or if she had already trained the cat to use a regular toilet and hoped his skills would transfer...

Personally, I really hope the cat was trained to use the toilet. I feel like we all should live in a slightly more magical world where this is common.

To answer the question, YES - you can put pet waste in a composting toilet. In fact, some veterinary clinics have installed composting toilets for this purpose. Side note, if you have trained your pet to use an actual toilet, please let us know. That sounds incredible. 

5. How Often Do I Have to Empty a Composting Toilet?

This is one where the answer isn't so cut and dry. You have to consider a few key factors, like how often it's gonna be used, how much it can hold, and what kind of composting system it uses. If it's just going to be a couple of people using it, any of our recommended units should do the trick. Emptying the unit is in the 1-2x per month up to 1x every couple months.

If you have a whole squad or a family sharing the unit, you might want to opt for one of the higher-capacity models. Some of these composting toilets can be used continuously and go an entire season without emptying. Plus, all toilets listed on ShopTinyHouses come with easy-to-use emptying systems. Think of it like taking out the trash - is it fun? No, but it's not a big deal. 

6. How Do You Get Rid of the Solid and Liquid Waste?

The easiest option is to try using urine as a fertilizer. You can dilute it with water in an 8:1 ratio to make a great liquid fertilizer for your plants. Don't worry about the smell - there won't be any.

For getting rid of the compost from a composting toilet, it depends on the model you have. Some toilets available complete the entire composting process and can be dumped in your compost pile immediately. Others might need a bit more time to complete and could be stored in a spare compost bin or composting chamber until finished. It's also completely acceptable to dump it into a garbage bag and toss in the trash, although that's not as eco-friendly.

7. What Is the Most Important Thing to Consider Before Buying a Composting Toilet?

You've probably already considered this, but the most important thing to take into account is its capacity, location, and functionality. The capacity refers to the amount of waste that can be stored in the unit before emptying is required, while the functionality refers to the toilet's features and how you'll use it.

It is essential to determine the right size of the toilet based on the number of people expected to use it and the frequency of its use. If you have a large group using the toilet full-time, we would highly recommend one of the larger capacity models like Sun-Mar Centrex 2000/3000 or the Biolet 65A. If 1-3 people are using the toilet full time or even a few more people part-time, then any of the models will work well.

Beyond capacity, your space and location needs are really important. Is this your new RV composting toilet or is it for your tiny home or off grid cabin? Many composting toilets would work in LOTS of different locations. But if you plan to take it out and move it often, only a few composting toilets are also portable. Some models have electronic indicators to help you know when to empty the toilet, some models use electronic agitators inside of the toilet while others require manual turning. It really just depends on what you want. The truth is that if you're considering a composting toilet, you can find one that matches your needs.

8. Are Composting Toilets Legal in My State?

A great question. Clearly, we're retired lawyers who got into the Toilet Biz... In all seriousness, though, this is a very important question. We took some time and created a document that we update regularly. The answer is that for most states, YES, it is legal. However, some jurisdictions require specific permits. A few states still have not come around to the composting toilet world... looking at you, Indiana.


Will My Bidet Attachment Connect?

Well... yes, you can.

What makes this strange is that most composting toilets are usually waterless or dry toilets and users often do not have or want water hookups for the toilet. Also, you don't want the extra moisture in the composting solids bin. If you do want to hook up a bidet attachment, you need a way to handle the extra moisture that comes with it.

One option is to have a designated "bidet toilet" for your cleaning needs. And guess what? You can keep things easy breezy with a portable bidet that doesn't require a fancy running water hookup.

9. Is It Hard to Install a Composting Toilet? I'm not very handy...

This is a super common question. One of our team members is terrible with tools and has broken a thumb or two... but he still loves his tiny house.

Truth is, each brand is a bit different. Some require mounting to prevent the toilet from moving, which is especially helpful after establishing ventilation. Others only require mounting if you are using it in a moving unit such as a boat or RV. Some even offer additional lift kits or specialty options to customize for your needs. 

All of the composting toilets come with their own mounting hardware and kits. Every toilet unit that requires mounting has instructional guides and additional resources to help you install the toilet and any venting, if it is required for use. For some models, such as the Laveo Dry Flush, additional lift kit options are available separately as well.

10. Can I Use Toilet Paper in My Composting Toilet System?

Yes, all the composting toilets on the market that we recommend accept toilet paper... just like a regular flush toilet. Unlike some RV and camper toilet systems, you don't have to buy any special kind of toilet tissue paper either.

We do recommend using a single ply paper or tearing individual squares and stacking them rather than using a long combination of connected squares, though. For some models this won't matter, but for others (like Nature's Head or OGO), this will prevent the agitator from getting slowed down. 

11. Can I Build My Own? Why Do Composting Toilets Cost So Much?

You can certainly build your own! If you're really handy and have the time, then definitely go ahead and build one. Our advice is to focus heavily on the ventilation as smell might be a challenge.

Composting toilets tend to be more expensive than traditional flush toilets due to a few factors. First, they require a more complex design and technology to properly contain and compost human waste without producing undesirable odors or harmful pathogens. This often means that higher quality, more durable materials must be used in their construction.

It is important to note that upfront costs of composting toilets can be offset by long-term savings on water and sewage bills, making them a financially beneficial option in the long run. 

12. Do You Need Electricity to Use a Composting Toilet?

It depends on the type of toilet. Some composting toilets require power to run the ventilation fans and a few require power to display capacity levels or even to help flush the unit. If you don't have electricity, there are several composting units that don't require any power. 

13. Do You Need to Run the Fan All the Time?

Depending on the type of unit, yes. Your self-contained composting toilet may require running the fan frequently to ensure continuous ventilation, which can also help break down the waste.

Some models don't require ventilation, but if they do, the manufacturer will include ALL of the hardware you'll need, including any attachments, fan vents, tubing and more. They also include a power connectors if fans are required and we offer alternative power hookups if you need them.


Is the toilet seat a normal size?

Yes, like a typical toilet, composting toilets use a standard toilet seat size. All of our recommendations on ShopTinyHouses are weight rated up to 500 pounds or more as well. 

14. How Do I Keep the Bowl Clean?

We like to keep a spray bottle next to the toilet with a white vinegar and water mixture (2oz white vinegar and the rest water) and spritz the bowl after urinating. It works great for wiping the exterior as well and neutralizes any odors.

15. What Is the Best Composting Toilet for Your RV or Tiny House (or Camper, Boat, etc)

You will hate this answer... but it just depends on what you need. The right composting toilet in your RV might be different than the one I'm using. For example, I needed a compact composting toilet because my space was really tight so I got the OGO. For you, the Nature's Head with a Spider Handle might fit perfectly.

With a tiny home or off grid cabin, some of our customers prefer an entire composting system in a single, whole toilet (such as Nature's Head or OGO) while others prefer models that look like regular toilets (such as Dometic or Separett toilets). 

It just depends on you.

If you're looking for the best composting toilet, focus first on your specific circumstances. If you haven't taken our Composting Toilet Quiz, do that next (link below). If you think you know what you're looking for, but to compare toilets, check out our "Head to Head Mini Guide" series.