homecatalogdealer locator


Learn how we build our toilets on How It's Made

SUN-MAR Toilets used for
Mars Mission

As seen on
Building Wild

See SUN-MAR on
Tiny House Nation

Look for SUN-MAR on HGTV's Tiny Luxury

Catch SUN-MAR on
Treehouse Masters


Producing no pollution and leaving no footprint SUN-MAR composting toilets are the future for a greener earth.
More on the environmental benefits


SUN-MAR composting toilets evaporate the liquids and odorlessly decompose the remaining waste into an inoffensive fertilising soil
More on how they work


Because people like to see a composting toilet before they buy, we have a large dealer network right across North America
Find a dealer near you






Toilets from $629 and up

Sun-Mar on TV

Sun-Mar in the News

Sun-Mar References
    Click Here to See Central  Composting Toilet Systems Click Here to see Self-Contained Composting Toilet Systems Click Here to see Self-Contained Composting Toilet Systems Click Here to See Central  Composting Toilet Systems

follow us on
social media


SUN-MAR has a composting toilet for every need.
- Electric or non-electric
- Waterless or 1 pint flush
- Small, medium, or large capacity units
More about our units


SUN-MAR's unique and superior composting toilet designs are covered by international patents and feature 3 separate independent chambers with Bio-drum for composting, finishing and evaporation
More on SUN-MAR's 3 chamber technology


What you should know before you buy a Composting Toilet
     Importance of NSF Certification

Only SUN-MAR's composting toilets are certified by the National Sanitation Foundation for residential and cottage use
   Official NSF Listing



 What SUN-MAR Composting Toilets do

SUN-MAR composting toilets recycle waste on-site by evaporating the liquids, and converting the solids to a fertilizing soil which is perfect for uptake by plants. SUN-MAR composting toilets use naturally occurring aerobic bacteria to convert the carbon atoms in the waste to carbon dioxide, and the hydrogen atoms to water. In this way the waste is oxidized and reduced to its essential minerals. Since waste is some 95% moisture, after the liquid has been evaporated and the solid waste composted, the residual is only about 3% of the starting volume. 

 This recycling process avoids the need for sewers and central treatment plants. It also avoids invasive on-site treatment systems such as septic systems.

SUN-MAR composting toilets are recycling marvels that are odorless, leave no footprint, do not pollute in any way, and can be installed anywhere a toilet is needed. Indeed a SUN-MAR is so obviously good for the planet that at SUN-MAR we wonder why everyone is not using them!

The First Generation Waterless Composting Toilet

The founder of SUN-MAR, Hardy Sundberg, developed the first self contained composting toilet in 1971. This waterless toilet had a fan and heater at the top, blowing hot air onto the waste pile which was agitated by mechanical mixers. As the compost in the bottom was agitated it fell though a screen into a collection chamber.

While at the time this toilet represented a big step forward in the development of composting toilets, in hindsight it can be seen to suffer from a number of weaknesses. Firstly, this composting toilet design was what we now call a single chamber unit, which means that the operating conditions were the same throughout the whole toilet and not optimized for the different needs of composting, evaporation or finishing. Secondly, the fact that heat was being blown in from the top meant that the compost tended to get dried out, while the liquid in the bottom was not evaporated efficiently. Thirdly, the compost in the bottom was not isolated and was subject to contamination from fresh waste.

Even today, over 30 years later, some waterless composting toilets can still be found which feature a top mounted heater with all the attendant problems this brings. However, subsequent SUN-MAR composting toilet designs have been successful in solving the inherent problems evident in this first waterless toilet design.

The Second Generation

In 1977, the second generation composting toilet was born. Known as the Tropic, this waterless toilet featured one highly significant improvement; the heater was located in a sealed compartment in the base of the toilet. This base heater was able to evaporate the excess liquid in the base, while allowing the compost pile to remain moist, an improvement which dramatically increased composting speed and ease of operation.

This heater arrangement therefore overcame the big problem with top mounted heaters, namely that in evaporating liquid they also dry out the compost pile. Drying out the pile has two undesirable affects. Firstly, aerobic microbes are reduced to the point where composting slows to a halt, and secondly the waste cakes to a consistency somewhat like an adobe brick where it becomes impossible to agitate the pile.

The First Central Composting Toilet System was Marketed

In 1977 SUN-MAR extended the concept of domestic composting by offering a composting toilet system that was outside and several feet away from the bathroom, but connected to a 1 pint toilet in the bathroom. This allowed users to have a ”normal” looking bathroom, while still having all the benefits of composting. The use of a low flush toilet meant that compost was much easier to keep moist. However because this toilet was not waterless, it was not always possible to evaporate all the liquid. Consequently, the small amount of excess liquid has to be handled by an old septic, recycling bed, or other approved system.

The Third Generation

In 1979, a further major improvement was launched. The difficulty of aerating and providing oxygen for the aerobic microbes was solved by replacing the pile and mechanical mixers by a Bio-drum. The Bio-drum had a door which when open allowed the waste into the Bio-drum, and when shut allowed the Bio-drum to stay sealed when rotated. This Bio-drum arrangement gave rise to a huge performance improvement because by rotating the drum compost could now be well mixed, and perfectly oxygenated, while also allowing the moisture to be evenly distributed throughout the compost.

This Bio-drum had a screen in the rear, which allowed any excess liquid to drain into the evaporating chamber in the base of the composting toilet, thus ensuring the waste did not get saturated. Saturated waste is undesirable in a composting toilet because it dramatically slows composting down by driving out the oxygen the aerobic microbes need to survive. A saturated compost provides good conditions for anaerobic microbes, which are slow and odorful.

Another major benefit to the Bio-drum arrangement was that by rotating the Bio-drum backwards, the Bio-drum door would remain open so that the compost would drop automatically into a finishing drawer. In the drawer, compost was isolated, no longer exposed to fresh waste, and was able to finish composting while gradually drying out. The drawer could be easily removed without exposing the user to liquid or fresh waste.

This was the first three chamber composting toilet, where composting was taking place in the Bio-drum, liquid was being evaporated in the evaporating chamber and compost was being finished in a finishing drawer. All these essential processes could now be optimized, a development which gave SUN-MAR the leadership position in the field of composting toilets-  one which it has maintained to the present day.

The Advantages of a Three Chamber Composting Toilet

Some of the advantages have been described above. Hopefully repetition will do no harm!

1. The three different chambers allow for optimizing the three different requirements for composting, evaporating and finishing.

2. The Bio-drum allows compost to be properly and completely oxygenated, rather than the partial aeration achieved by composting toilets with fixed mechanical mixers.

3. The Bio-drum ensures there is no excess moisture, since any excess is automatically drained to the evaporating chamber.

4. By being separated from any direct heat, the material in the drum does not dry out as it would in composting toilet designs where heat is aimed directly at the pile.

5. The drum offers simplicity of operation. Tumbling the Bio-drum ensures mixing is easy and complete( like a cement mixer or clothes dryer).

6. Removing compost is merely a question of rotating the Bio-drum backwards. There is no concern with sealed bases, secured by screws and there is no exposure to liquids and flooding.

7. The Bio-drum offers the ideal environment for aerobic bacteria to prosper.

8. The evaporating chamber is heated by a heater below it. The advantage this gives is similar to the advantage gained by heating a saucepan with an element beneath, as opposed to heating with a hair dryer from above.

9. The heater is on when there is liquid to evaporate and off most of the time when there is no liquid.

10. The evaporating chamber offers the ideal environment for evaporation.