Sun-Mar Composting Toilets Brand Review & Buyer’s Guide



Written by Oliver. Last updated:

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While it is certainly not the most glamorous subject, the decision to live off-grid will require you to put some thought into waste management. When you don’t have access to a standard plumbing network, you can’t simply install a regular flushing toilet, which is why you need to get a little bit creative.

Fortunately, composting toilets have come along as a practical and affordable solution. Not only can they function without flowing water, but they also do not even have to be connected to a sewage hookup or a septic tank, which means they are completely self-contained units!

Whether you travel by RV, boat, or camper van, or you simply own a fixed, off-grid dwelling, like a tiny house, cabin, or full-sized off-grid home, a composting toilet can be a practical solution when you do not have the option to install a flushing toilet.

How Can We Help?

If you are in a situation where you believe a composting toilet could be beneficial, you might be wondering which brands make the best models. To help you understand your options, we are going to offer an in-depth review of one of the current top brands in the industry – Sun-Mar.

Not only will we explore the brand’s history and its reputation within the industry, we will take a close look at some of their best-selling composting toilets. From there, we will offer our overall impression of Sun-Mar composting toilets and decide whether or not we would feel comfortable recommending their products to our readers.



Sun-Mar was originally founded in 1983, so they have been around for quite a long time, especially compared to their competitors. The brand’s origins can be traced back to when the founder, Hardy Sundberg, invented the world’s first self-contained composting toilet in 1971.

This invention meant that, for the first time, a self-contained toilet was capable of evaporating liquids and composting solids at the same time. This meant that living off-grid could have an indoor waste management system that was far more comfortable than a basic hole in the ground. The ability to have an indoor toilet that did not rely on municipal waste infrastructure was a major leap forward for off-grid living.

In 1979, Hardy added a three-chambered rotating drum to the compost chamber of his composting toilet. This greatly improved aeration and the rate of decomposition. In fact, all of Sun-Mar’s current models still incorporate this original design, which is a testament to its effectiveness.

In 1983, Hardy Sundberg decided to use the popularity of his composting toilets to form the backbone of a new company by incorporating and founding Sun-Mar. Today, the brand continues to operate out of its original headquarters in Ontario, Canada. They also have manufacturing and distribution facilities in New York, USA.

They now sell their various composting toilet models and accessories around the world through a network of thousands of trusted dealers. If you have used a composting toilet in the past, there is a good chance it was a Sun-Mar!

Brand Mission & Reputation

Sun-Mar proudly assembles and builds all of their composting and recycling products themselves, including their popular composting toilets. Not only is it important to them that they continue to support domestic jobs, they believe that composting is one of the best ways that people can do their part to protect the environment, which is why they continue to focus on chemical-free, waterless waste management solutions.

Today, all of their products are designed with the comfort of the user in mind, as well as preserving the natural world and protecting the environment. The brand continues to be motivated by their overarching desire to be one of the global leaders in recycling technology, an aim they hope to achieve through continued research and innovation.

In terms of its reputation amongst consumers, Sun-Mar is one of the most respected brands in the off-grid community. Their composting toilets work exceptionally well and find the perfect balance between affordability and quality. As we mentioned above, there is a good chance you have come across a Sun-Mar composting toilet if you have ever spent any time in an off-grid dwelling or mobile home.

Why Choose a Sun-Mar Composting Toilet?

We were curious as to why Sun-Mar composting toilets continue to be amongst the most highly regarded composting toilets in the industry. This is why we decided to take an in-depth look at what sets their products apart. After we have explored the reasons why Sun-Mar composting toilets are so popular and effective, we will take a closer look at some individual models.

Sun-Mar’s Unique and Patented Bio-Drum

One of the defining features of a Sun-Mar composting toilet is the addition of its unique Bio-Drum. In simple terms, the Sun-Mar Bio-Drum helps create the perfect environment for the decomposition of organic material.

It achieves this by regulating the temperature, amount of moisture, and level of oxygen within the drum. By spinning as the matter decomposes, the Sun-Mar Bio-Drum is able to maintain the ideal level of aerobic microbes, which work together to quickly break human waste down and convert it into a soil-like substance.

Effective Moisture Control

Whenever organic matter contains above 60% moisture, the liquid can start to drive out the oxygen required for decomposition. Sun-Mar composting toilets are specifically designed to drain away excess liquid through a unique screen system. The liquid is then driven to an evaporation chamber.

With that being said, the toilets do not completely pull all of the moisture out of the composting area, as this would also slow the composting process. A unique moisture control feature keeps everything in the ideal conditions, which means that their toilets help break matter down faster than a conventional composting toilet.

Consistent Oxygen Supply

The toilets also help to oxygenate the organic material as it is broken down. Unfortunately, most composting toilets that attempt to do the same generate unpleasant smells, however, thanks to the unique Bio-Drum, Sun-Mar composting toilets are able to pull in an appropriate volume of fresh oxygen, without emitting unpleasant smells and gasses.

You get all of the benefits of a highly oxygenated decomposition tank, without having to deal with any of the negative consequences.

Fully Off-Grid Operation and Ease of Installation

One of the main selling features of Sun-Mar composting toilets is the fact that they are designed to operate completely off-grid. Even if you opt for one of the models that feature an exhaust fan, you have the option to supply power to the fan using a solar panel.

While the fan is not required, it does help to reduce the presence of detectable odors, as it will help pull air from the toilet and force it outdoors through a vent.

Each of Sun-Mar’s composting toilet models is designed to be fully self-contained, which means they do not need to be hooked up to any sort of pipe network and they do not require water. You simply install the toilet in as little as an hour, then the job is complete. Since you do not need to hook it up to a power supply or make any plumbing connections, the installation process can be completed without any sort of professional assistance.

The Top Sun-Mar Composting Toilet Models

While all of their composting toilets follow the same basic design, meaning they all make use of the patented and effective Bio-Drum, Sun-Mar now has several models to choose from.

Their smaller models are ideal for RVs, boats, barns, pool sheds, cabins, and more. On the other hand, their central composting toilets are designed for larger indoor spaces and more frequent use. These models work exceptionally well for off-grid homes, cottages, cabins, warehouses, and so much more.

We decided to review three of their most popular models, which should help you discover why Sun-Mar composting toilets continue to be such a popular option.

The Sun-Mar Excel Self-Contained Composting Toilet

The Excel is Sun-Mar’s top seller and it also happens to be their flagship composting toilet. It is actually one of the best-selling self-contained toilets in North America, which is a testament to its performance capabilities and overall quality.

Like all of Sun-Mar’s composting toilets, it features a high-capacity Bio-Drum, which is incredibly easy to operate. The Bio-Drum gives the toilet the ability to deliver the same reliable results we have come to expect from a Sun-Mar composting toilet. The Excel also features a built-in exhaust fan, so you can choose to plug it in if you have access to electricity.

As it turns out, the Excel was actually the first self-contained toilet to ever get full certification from the National Sanitation Foundation, so when you choose the Sun-Mar Excel, you are choosing a composting toilet that has truly set the standard for the entire industry.

What we like most about Sun-Mar Excel is the fact that it is incredibly versatile. It has a large enough capacity rating that it can be used for just about any application, including installation in a full-time residence or a remote commercial space with light foot traffic. With that being said, it is still compact enough that it is a practical option for an RV or camper van.

The Excel is even available in two distinct colors, a classic white, and a cream/bone color. It is incredibly compact and even features a retractable stepping stool. When it is installed correctly, it looks just like a more compact version of a conventional flushing toilet, so it will not look out of place in any sort of dwelling.

Overall, it is an outstanding composting toilet that functions incredibly well. It is easy to maintain and empty. It also produces very little odor, so it is perfect for indoor use. We really can see why the Sun-Mar Excel is the brand’s best-seller.

You can click the following YouTube link to view Sun-Mar’s Introduction to the Excel Self-Contained Composting Toilet for more information.


  • Residential or continuous use – 2 adults or a family of 4
  • Seasonal or vacation use – 4 adults or families of 8

Venting Requirements:

  • Vent pipe – One 2” thin wall PVC pipe
  • Drains – 1” OD (This is optional unless you are planning on using the Sun-Mar Excel on a daily basis).

The Sun-Mar CENTREX 2000 NE (Non-Electric) High-Capacity Composting Toilet

The CENTREX 2000 NE is the non-electric version of the CENTREX 2000, so it is ideal for off-grid locations that require a composting toilet with a higher capacity rating. It is fitted with a 4” vertical vent stack, so it is fairly easy to install and can be positioned just about anywhere.

Like the Sun-Mar Excel, the CENTREX 2000 NE makes use of the patented Bio-Drum, but it is large enough that it is a practical solution for full-time dwellings that have multiple residents. Not only can it hold more waste, its larger capacity means that it can support a much longer composting cycle, so you will not have to empty it nearly as often as a typical composting toilet.

The CENTREX 2000 NE does not come with the actual toilet, so it is compatible with your choice of any low flush toilet. This allows you to outfit your dwelling with a normal-looking toilet, so you can have all of the comforts of the city from your off-grid home.

When you consider the many benefits it offers, there is no wonder why it is one of Sun-Mar’s top sellers.


  • Residential or continuous use – 3 adults or a family of 5
  • Seasonal or vacation use – 6 adults or families of 8

Venting Requirements:

  • Vent pipe – One 4” thin wall PVC pipe
  • Drains – 1” OD (This is required for all applications with the CENTREX 2000 NE)

The Sun-Mar Compact Composting Toilet

As the name suggests, the Sun-Mar Compact is the brand’s lowest-profile composting toilet. While it is much smaller than a conventional toilet, it has a completely normal appearance, so it will complement any bathroom.

Despite its small size, the Sun-Mar Compact still contains the effective Bio-Drum, which is thanks to the fact that their engineers were able to create a drum with a much smaller diameter. In fact, the drum is smaller at the front of the toilet and expands towards the rear.

If you are limited on space, the Sun-Mar Compact is the ideal solution. This is why it has proved so popular with RV enthusiasts, those who travel by camper van, and those that are looking for a practical marine toilet for their boat. With that being said, it would still work just as well in any land-based, off-grid dwelling.


  • Residential or continuous use – 1 adult or a family of 2 with more frequent empties
  • Seasonal or vacation use – 2 adults or families of 4

Venting Requirements:

  • Vent pipe – One 2” thin wall PVC pipe

Drains – ¾” OD (This is optional, but should be used for full-time residences).

Pros & Cons for Sun-Mar Composting Toilets


  • Moisture control helps speed up decomposition and manage unpleasant odors
  • Unique Bio-Drum helps with aeration and the maintenance of a healthy bacterial balance, both of which help speed up the rate of decomposition
  • Incredibly easy to empty the liquid and solid tanks when necessary
  • The brand continues to manufacture its composting toilets in Canada and the United States, rather than in low-cost, off-shore facilities
  • Three chamber system works incredibly well
  • All of their toilets can function completely off-grid, meaning no septic or sewage connection is required
  • Operates without chemicals, water, or any other additives
  • They maintain National Sanitation Foundation (NSF) Certification, which means their products are tested every 6 months through an independent testing laboratory under strict conditions. This means all of their composting toilets are completely odor-free, even while operating at maximum capacity!
  • Variety of sizes and styles, so you can choose an option that works for you

They have been involved in the composting toilet industry for over 35 years


  • Some of the larger models, like the CENTREX 1000 and the CENTREX 2000 NE, only come with the composting system, so you need to purchase a toilet separately. However, this allows you to pick the exact toilet that meets your preferences

Certain models function better with the motorized exhaust fan, so you may need access to electricity for the best possible results. With that being said, the electric motor draws very little power, so you can get away with a small solar power system, or a compact solar generator, like the EcoFlow RIVER MAX

Our Final Impression of Sun-Mar Composting Toilets

After taking a deep dive into the Sun-Mar brand and looking at some of their most popular composting toilets, we found ourselves fairly impressed with what they have to offer. When you consider that they have been around longer than just about any composting toilet company and their products remain as popular as ever, it really becomes difficult to argue with the fact that they are a very trustworthy brand.

We like that they offer so many different models in varying capacities, as this makes it easier for consumers to find the perfect composting toilet for their particular living space. Whether you are looking for a compact composting toilet for your RV or tiny house, or you need something with a much larger capacity rating for a cabin or off-grid home, you will be able to find exactly what you need by shopping Sun-Mar’s impressive product catalog.

Their unique three-chamber system and patented Bio-Drum really help to speed up the rate of decomposition, which means you do not have to empty a Sun-Mar composting toilet nearly as often as you would have to empty a similarly sized toilet from another brand. For RV enthusiasts, this means far fewer stops.

The increased rate of decomposition also helps with odor control. As with any indoor composting toilet, odor management is one of the most important factors you will want to take into consideration when assessing your options. Fortunately, we could not detect any sort of unpleasant odor when we examined our Sun-Mar composting toilet, even after it had been used for several days. If anything, the smell is reminiscent of soil and it is only detectable when the toilet lid is up and you are standing right beside it.

Overall, Sun-Mar composting toilets hold up extremely well and we believe the brand is certainly worthy of our recommendation.

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