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Tiny House Toilets: way more than you’ve ever wanted to know

TinyHouseFran tiny-house-products 9 Comments

Warning: in talking tiny house toilets, we go into detail. We want to be as informative as possible, so in the following article we provide as much info as we can about everything related to tiny house toilets. This includes using and cleaning the discussed models of toilets. 

When talking to friends, family, and strangers about my tiny house, I constantly get asked about the toilet situation (typically after a few drinks). People are fascinated. While some make crazy assumptions, most have no clue what the options are for tiny house owners. I’m hear to spread as much knowledge as possible, and to also review my last two toilets.

tiny house toilet

First, let’s lay some groundwork and talk “types” of tiny house toilets. There are three major categories to choose from.

What are my options for Tiny House Toilets?

1. “Regular” flushing toilet

This is very common in recreational vehicles (RV’s), but not at all typical for tiny houses. For a flushing toilet to work, a “black water tank” is required.

When this tank is over 2/3rds full, it can be disposed of at a proper “dump station.”

We at TinyHousehold.com have very little experience with this type of toilet, so can’t intelligently speak to the advantages and disadvantages.

2. Incinerating toilet

As it sounds, this takes deposits and turns them into ash via an internal incinerator. During the process, it eliminates all pathogens. Typically, these are powered by gas, electricity, or dried waste.

Due to all of this burning action going on, these units require a significant sized ventilation system, which we see as one downfall. You can have the most advanced exhaust system installed, but we still have doubts that there will be no odor remaining form burning human waste. We’ve also heard feedback that between the incinerating process and exhaust system, that this type of tiny house toilet can be quite noisy.

Additionally, we’re a bit skeptical about introducing fire within an enclosed space… we’ll leave that to the oven. One last item of note is the maintenance. We’ve heard that the incinerating toilet can get a bit challenging in this department. Check out “incinerating toilets’ on YouTube at your own risk!

If you have one of these units, we’d love to get your feedback in the comments below. Don’t be shy – let us know what you think of our evaluation of the flaming toilet.

3. Composting toilet

We’re unabashedly biased towards this third type of tiny house toilet. The composting toilet is a “dry toilet” that uses an aerobic processing system to treat human waste by composting or decomposing it. These typically use little to no water. Waste is mixed with a decomposing agent like sawdust, cocoanut, or peat moss.

Of the composting toilet family, there are two siblings.

  • Non-Diverting toilets:  this catches both liquids and solids within the same tank. My previous toilet, a Sun-Mar Mobile, was of this variety.
  • Diverting toilets: this separates liquids and solids into separate tanks. My new tiny house toilet, the Airhead, is a diverting model.

Now that we have the basics down, let’s check out a comparison of the diverting and non-diverting models. I’ve personally owned both types of composting tiny house toilets – the diverting model (Airhead) and the non-diverting (Sun-Mar). I’ll compare the two in detail in hopes that you get a better idea of which you’d prefer.

Sun-Mar Mobile

Type: Compost, Non-Diverting

I used the Sun-Mar Mobile composting toilet for the first two years that I owned and lived in my tiny house. It’s a Non-diverting, composting model. Here’s the premise: 90% of toilet waste is water content that can be carried back into the atmosphere. As such, all liquid within the bulking material is drained into the “evaporation chamber,” and magically disappears through the ventilation stack and into the atmosphere. While this sounds simple enough, it actually takes a lot of care and attention, which we’ll later discuss.

sun mar tiny house toilet

Installation

The toilet unit itself comes fairly complete. I would have loved to document the “unboxing” process for our community, but it was during my Tiny House Nation episode, so I didn’t get the chance. However, I did have to install it myself, so I can pass on that wisdom as best as possible.

The unit isn’t so tiny in terms of weight, weighing roughly 40 lbs. As far as dimensions, the Sun-Mar Mobile measures 30′ in height, 19 1/2′ in width, and 23′ in depth, requiring another 38′ to remove drawer.

To fasten the toilet to the floor, it comes with two brackets. This is important if installing the unit in a boat or trailer that will be moving around a lot.

For power, a 12V 120 Watt plug is needed for the evaporation chamber and the fan will need a 5.4 (12V) hookup to take the toilet odors up and out to the birds.

Before committing to a permanent home for your new throne, know that there’s two very important exit points needed.

toilet ventilation

#1 Exit Point – Ventilation exit

For this, you’ll need to drill a 3 inch hole into your tiny house… scary, right?! But, scarier is having no ventilation for your tiny house bathroom. Once you get that PVC through the hole, you’ll need a flange to prevent water from seeping in. You can get this at any major big box store.

I have a couple pointers that you should really take into consideration if / when installing a similar tiny house toilet.

  • Do NOT have a 90 degree turn in your vent shaft! Keep it at a 45 degree angle exiting your house. This increases airflow, which is important for obvious reasons.
  • Make sure your vent shaft goes above your roof line! The last thing that you want is the fumes getting piped into the side of your house.

Below the exhaust fan will be a Zeolite and Carbon filter. The fan will require a separate 12V hookup. I was able to run mine under my trailer and back up to my converter so it would be powered on at all times.

The Zeolite and Carbon filters absorb the smell and will get saturated roughly every couple months. At that time, they’ll need to be swapped out before getting too stinky.

#2 Exit Point – Excess drainage pipe

This 1′ pipe (exiting through the floor) is necessary for any non-evaporated liquids that may overflow from your tiny house toilet. Without this essential exit point, YOU WILL experience some extremely foul smelling liquid finding its way to your bathroom floor.

Once you have the vent shaft installed and the excess drain in place, you can finally plug in the unit! The plug is attached to the heating plate on the bottom of the unit. This is there to evaporate any excess liquids from the bulking material.

NOTE: there will be excess liquids… especially after poker night with the guys.

Usage

Don’t worry, this isn’t about actually using the toilet, but rather the process before and after you’re able to do your business.

The Sun-Mar user’s manual is straightforward. You have options for bulking material that they provide. Once you’ve decided and have placed this in your drum, you’re ready to go. Both liquids and solids are deposited right into the bulking material.

You’ll need to add one scoop of material every day. NOT every time you use the toilet, but rather just once per day. This will prevent it from getting too dry.

Sun-Mar has a patented drum technology that separates the liquids from the solids. The solids stay in the drum and the liquids get directed to the evaporation chamber. You’ll need to rotate the installed drum handle on the unit every other day. Additionally, you’ll want to spray an aerobic accelerator and an enzyme every two weeks. The solids will decompose within the drum.

Once the drum is filled to the halfway point, there’s a piece that the user pulls while rotating the drum. This drops the content into a drying chamber where it sits for 4-8 weeks to decompose.

Maintenance

Moisture Levels

It’s somewhat of a delicate process to keep the proper level of moisture within the drum. If it gets too moist, it will begin to smell. If too dry, you’ll start to attract flies, which are very hard to get rid of. Again, I want to stress – you must have the drain for excess liquid hookup installed. This is vital to keeping sewage off of your floors.

When you see the bulking material look moist and glisten in the light, then you have a good moisture level. If the material becomes very dry, you’ll need to add warm water at the end of the day if the toilet hasn’t been used.

Rotating the Drum

It’s tempting to want to rotate the drum every time you use the toilet. We’re creatures of habit and are used to flushing, right? But, keep it to once every two days. This will allow for better decomposition. If you’re constantly rotating the drum, you’ll create balls of waste that won’t decompose.

sun mar tiny house toilet workings

Adding Spray & Microbe Mix

Every time you rotate the drum (remember… every two days), you should be spraying “Compost Quick” into the mixture. This introduces enzymes that allow for a quicker decomposition.

Every two weeks, you’ll be adding the “Microbe Mix.” You’ll see a little cup included with the mix. This helps to introduce important microorganisms to assist in the breakdown.

Very few stores sell these products. I order them online. You can find both on Amazon below.

tiny house toilet maintenance

Emptying the Tray

I know this is what you’ve been waiting for. It’s inevitable. There comes a time when you’ll need to empty your composting toilet and remove the hopefully decomposed material from your tiny house, sailboat, RV, or wherever you’ve been pooping.

The Sun-Mar toilet has a tray that sits under the entire assembly. It holds material dried out over a 4-8 week time period. To remove the tray, you need to first undo four plastic screws, then slide the unit out.

Remember: there is a 38′ space required to remove the tray. It would be terrible to install your tiny house toilet, use the bathroom regularly for 8 weeks, then find out you have no room to slide the tray out!

Once you slide that out, the contents are sitting there in the tray. Don’t trip. You’ll then empty the decomposed waste into a proper composting bin or other receptacle as allowed.

After that’s emptied, you can clean the tray but be sure to only use Compost Quick and water on that tray. Do NOT use common household cleaners! You’ve built up a special ecosystem here for breaking down waste and typical cleaners will wipe that out, which is not good.

Spray the lining of the tray with your Compost Quick and you can reinsert the tray. You can now start emptying the drum again.

Airhead Toilet

Type: Compost, Diverting

This is the tiny house toilet that I recently installed and have had in my home for just over a month now. The Airhead model that I have is a diverting, composting toilet. As described above, this means that the liquids are diverted to one chamber and solids to another. This is achieved through a retractable hatch (see image), which diverts liquids to the front of the toilet and into the designated chamber.

airhead diverting toilet

Installation

As you can see from the included images, the Airhead toilet was very neatly packed. The actual installation was incredibly simple and involves only two pieces. The Vent Hose Connection (with this piece, you’ll want to use both glue and three screws to make sure it’s secure) and the crank handle.

Once you’ve attached those two items, you’ll need to install the toilet itself into your tiny house (presumably in the bathroom). You’ll want to position the toilet in the desired location, then mark the exact spot for the brackets. These brackets are what hold the toilet down. Once marked, you’ll remove the toilet and screw these into place. The toilet should then slide right into these support brackets.With a few twists of the wing-nuts, it’ll be locked down. You’ll want to again remove the toilet to install the exhaust fan.

Unlike the Sun-Mar toilet, the Airhead is only venting air and not moisture. This means that the vent can actually point down and vent out of the bottom under your trailer (as long as there’s airflow under your trailer). If it’s on wheels, this is a perfect solution. This works very well for my personal trailer, which is a Tumbleweed Tiny House Trailer.

airhead ventilation

Once you find a good spot, use the appropriate drill bits to drill out the 2 1/4 hole in the floor. You can see this in action with the attached pics. I previously had a smaller hole for my Sun Mar and wanted to drill this out. To do so, I screwed down a larger piece of wood to create a continuous drill through the subfloor and out the bottom of the trailer. I inserted PVC and added a sealant around the PVC. After drilling the hole and sealing it, you just need to place the van shroud and gasket over it and screw it into whatever surface it’s touching. Now connect the provided hoses shown in the manual and that’s it, toilet ventilation!

The tricky part is done. Now you just need to place the top section of the toilet onto the bottom side and tighten those wing-nuts. Once in place, slide the liquids tank into place and mark the brackets. Repeat the same steps as before. Remove, mark and drill – and your toilet is now installed.

final installation

But, you’re not quite done yet. One more step. You’ll need to get power to the 12V fan. I had wiring previously in place from the Sun-Mar so I simply reattached the wires under the trailer up and next to my converter and connected them that way.

Usage

It’s very simple to use the Airhead toilet. Coconut coir (dehydrated coconut husks) is provided with the toilet for first usage. All you’ll need is a five-gallon bucket, water, and a little elbow grease to break apart the coir. The manual will provide the amounts needed and once all of the water is absorbed, you’ll add it to the toilet. Lastly, you’ll throw in the provided enzymes, and you’re ready to go.

With the Airhead toilet, you’re provided biodegradable coffee filters that are placed into the toilet to catch your solids and deposit them into the solids tank. I immediately ordered another 50 for $4. This may seem strange to discuss, but it’s part of the process. Doing this correctly will avoid messes, save cleaning, and stop the unnecessary usage of extra papers. Regular biodegradable coffee filters can be ordered on Amazon along with the coconut coir.

airhead toilet maintenance

You place one of the filters into the toilet bowl – have a piece of it under the toilet seat. Then, you do your business and open the hatch and lift the toilet seat. No mess. No fuss. No cleanup. Again, this may sound strange if you’re not familiar with tiny house toilets, but it becomes routine and isn’t overly involved after a few times.

The Airhead toilet diverts the liquids into the front of the bowl and to the liquids tank. Solids are contained in the rear of the toilet. Very little (if any) liquids get mixed with the solids.

Maintenance

Maintaining your new tiny house toilet will take some getting used to. When it comes to maintenance of diverting vs non-diverting models, there’s varying opinions. A non-diverting toilet is more difficult, but requires less frequent maintenance. Whereas, a diverting toilet is more frequent, but in a more interesting way (in my opinion).

Emptying the liquids tank

Regarding the liquids, this is where maintenance is a bit more involved. Your liquids container will need to be emptied every couple of days, depending on the usage. Urine by itself is sterile, so it can be used to water your flowers if you’d like. It can be diverted into a French Drain, which is used to distribute liquids, in many areas. As a rule, always research your area before dumping as rules often vary based on location. For oceans, lakes, and streams, there can be “NDZ’s” (no dumping zones) enforced.

Emptying the solids tank

On a weekly basis, you’ll need to scoop out 20%-40% of the compost and replace with hydrated Coconut Coir or Peat Moss. This will keep the toilet from filling and give your waste additional time to compost, allow you to dump the toilet less often. Because this contains no liquids, it’s acceptable to put this into a biodegradable bag and dispose of in a trash bin. If you’d rather not waste perfectly good compost and humanure, you can start a composting pile for your flowering garden beds and put it to good use.

sun mar vs airhead toilets

Final Verdict

In my opinion, the Airhead, diverting model wins the tiny house toilet competition. I’ve had this model for the past couple months and can say, affirmatively, that I enjoy it significantly more than the Sun-Mar. We hope that the info provided above helps you make your decision!

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Comments 9

  1. Ummm…..only two? Where is a comparison of, for instance, the Nature’s Head toilet? Two toilets isn’t much of a comparison…..or are more comparisons/links to comparisons coming later?

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      Author

      We wish that we could buy every major brand of tiny house toilet to show our readers, Athena. Unfortunately, we’re not able to do that. Hopefully the post was still helpful.

  2. Thanks! Great (and detailed) info on those you have personal experience with. I’ve seen reviews of Nature’s Head, which seems to be very common in TH’s, but not much on other models. The only other review of incinerating toilets I’ve seen mentioned the motor was noisy and significant power use plus (I think) it mentioned some odor of burning waste. I’ve wondered about diverting vs nondiverting, so appreciate your descriptions. Was a little confused after reading #3… I think you swapped brand names. The descriptions of each toilet cleared that up. Thanks again!

    1. Post
      Author

      Oops, you’re right. I accidentally switched those. That’s fixed now, so thank you so much for the help!
      Also, we appreciate the helpful info on the Nature’s Head model and the added potential downside of incinerating models. I just added that piece of feedback (the noisy motor) to the post. Again, thanks!

    1. Post
      Author
  3. Hi. I’ve used my Sun Mar probably for 5 years with great results. But now my household has become ‘we from me’ and I am ready to toss it to the curb side. We are having huge issues with the urine in the bottom not draining (which smells terrible!!!). Or the screen in the tub plugging. It has been apart more times than I care to report this past summer. My house smells like an outhouse. Besides that it takes up a huge amount of space in my bathroomeven with the tray not taken into consideration and it sits super high (even higher now that the toilet is elevated to help it drain because the drain outlet is about 2 inches up off the floor. If it doesn’t evaporate, the urine stagnates in the bottom. We have a non electric unit with a fan in the stack. We love the non electric, no water toilet. But Sun Mar is no longer an option. We are looking for another toilet.

  4. Hi, tiny house owner with an incinerating toilet here! We have an Incinolet RV model toilet that we love, and has an effective but not disruptive exhaust system built to release heat etc out of the side of our house (the wall behind the toilet). This was built by a certified electrician so I can’t speak too much to the nature of the installation but as far as I can tell was done flawlessly. The toilet is no louder than a small fan, and offers only a very faint burning smell AS LONG AS the ashtray is emptied weekly. If the ashtray is not emptied weekly (which we have learned by experience) it does get a little stronger of an odor. The ashtray is the easiest thing to dispose of, it’s just sterile ash with no hint of human waste in smell or appearance. The incinerating toilet is also super easy to clean and totally safe, the fire (totally contained in the metal incinerating chamber that only opens when you “flush”) only burns briefly and then the fan cycles on and off for 20-50 minutes to ensure total cremation of the waste. The only downside to the incinerating toilet for us is remembering to buy bowl liners (which can only be bought through Incinolet…and take about a week to arrive unless you shell out for rush shipping) we used freezer paper in a pinch once after reading up on any potential alternatives online but I would not recommend doing that. The bowl liners are relatively cheap if you fold them yourself (annoying, but worth it) and more expensive if you buy them pre-folded (I usually still get a box on hand for guests so I don’t have to explain how to fold AND then how to use the toilet…information overload!) Anyways, feel free to ask any questions!

  5. Very helpful information. We lived in our RV for five years and used the regular flush/black water tank system. It has the advantage of being much cheaper than the composter systems you just described. I was frankly really really shocked to find the composter is going to cost over one thousand dollars Canadian before installation. The disadvantage is you must have access to way to dispose of raw sewage. Reading your post I think the work of the backwater tank system is about the same as the composter system, less if you have a direct hook up to a sewer line. We currently live in a rural area in a tinier house (480 sq ft) with our own septic field except in winter. If we get to a place where repairing the septic field or switching to a simple holding tank and paying for that to be emptied is going to cost more than the composter, we’ll be switching. While we travel in our RV in winter, so many places are set up for the black water system, and so many dump sites are easily available, that I think we’ll stick to that. Meantime, really good to have that information for future planning.

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