Sun-Mar Composting Toilets – The World Leader in Composting Toilet Systems Since 1971

Sun-Mar composting toilets are the global standard that every other composting toilet in the market is measured against — and the reason is both the track record and the engineering: The Excel is the best-selling composting toilet unit in North America and for good reason — it is a high-capacity Bio-drum toilet that is very simple to operate, features well-proven technology, and is extremely reliable. The Excel was the first ever self-contained composting toilet to be certified by the National Sanitation Foundation. Sun-Mar has been a world leader in composting toilets for over 40 years — a 40-year track record of residential, cottage, cabin, and off-grid composting toilet installations across North America that no competitor can replicate. Sun-Mar's product lineup covers every composting toilet application an off-grid or sustainable property requires: the GTG urine-diverting unit for minimal space installations, the SpaceSaver for tight closet bathrooms, the Compact and Excel self-contained units for cabins and cottages, and the Centrex 1000, 2000, and 3000 central composting systems for full-time residential use and higher-capacity applications — all NSF Standard 41 certified, all backed by a 3-year warranty on parts. Adventure Motion carries the Sun-Mar composting toilet lineup for off-grid cabin owners, cottage builders, tiny home dwellers, sustainable property developers, and anyone building or upgrading a sewage-free waterless waste system. Contact Sun-Mar directly at 1-888-341-0782 for shipping quotes on specific models before placing your order.

✔ Over 40 Years as the World Leader — The Excel Was the First NSF-Certified Self-Contained Composting Toilet — The Excel was the first ever self-contained composting toilet to be certified by the National Sanitation Foundation. NSF Standard 41 is the toughest composting performance standard in the world — and only Sun-Mar self-contained units are listed for residential and cottage use by NSF.

✔ NSF Standard 41 Certified Across the Self-Contained Lineup — The Regulatory Approval That Matters for Permits — NSF Standard 41 certification is the approval document that local health authorities reference when issuing permits for composting toilet installations. Sun-Mar's NSF certification across the Excel, Compact, SpaceSaver, and other models means customers have the certification documentation needed for permit applications in jurisdictions that require it.

✔ Bio-Drum Technology — Patented Rotating Drum for Continuous Aerobic Composting Without Manual Turning — Sun-Mar's patented Bio-drum is the core technology that differentiates their composting process from static-pile alternatives. The rotating drum provides continuous aeration of the composting material — maintaining aerobic conditions that minimize odor and accelerate decomposition without the manual turning that static-pile systems require between uses.

✔ Self-Contained & Centrex Central Configurations — Self-Contained for Simpler Bathrooms, Centrex for Higher Capacity — Self-contained units contain the entire composting system within the toilet unit — no remote drum, no floor penetration, no separate installation below. Centrex central systems separate the composting unit to a remote location (basement, crawlspace, ground floor) and pair with a toilet above — providing the aesthetic of a conventional bathroom with the waste management of composting technology.

✔ 3-Year Warranty on Parts Across All Sun-Mar Models — Industry-Standard Coverage on Established Technology — All Sun-Mar composting toilets have a 3-year warranty on parts. Sun-Mar's 40-year track record and NSF certification history provide the institutional confidence behind that warranty coverage — manufacturer longevity that means warranty service is actually available when needed.

Sun-Mar Excel & Excel NE – The Best-Selling Self-Contained Composting Toilet in North America

The Excel is the best-selling unit in North America — a high-capacity Bio-drum toilet that is very simple to operate, features well-proven technology, and is extremely reliable. The Excel has enough capacity that it can be used just about anywhere: in residences, barns, and cottages. Composting capacity: 3 adults or family of 5 for residential use; 6 adults or family of 8 for weekend and vacation use. The Excel was tested by the National Sanitation Foundation at maximum capacity for 6 continuous months, during which the Excel produced no odor and produced clean, safe compost. The Excel NE (Non-Electric) version eliminates the electrical requirement entirely — operating without a heater or fan through a passive venting system, making it the correct choice for off-grid installations without electrical infrastructure. The Excel's 2-inch vent attaches at the top back and can be installed invisibly by running it through the wall and up the outside wall.

Best for:

• Off-grid cabin, cottage, and full-time residential owners who want the most widely proven, highest-capacity self-contained composting toilet available — the Excel's 40-year track record and NSF certification history that no competing self-contained unit matches
• Property owners in jurisdictions requiring NSF certification documentation for composting toilet permits — the Excel's first-ever NSF Standard 41 certification and continued listed status provides the permit documentation most authorities require
• Families of up to 5 for full-time use or up to 8 for seasonal use who need a single self-contained unit that handles the full household's waste without a central remote composting drum

Sun-Mar SpaceSaver – Smallest Self-Contained Unit for Tight Bathroom Installations

The SpaceSaver is a standard three-chamber unit designed specifically for situations where space is extremely limited. With a width of only 19" and depth of 22", even a closet or small corner can now be turned into a bathroom! Composting capacity: 1 adult for residential use; 3 adults or family of 4 for weekend and vacation use. The SpaceSaver is 30" tall, 19.5" wide, and 23" deep — weighing 43 lbs. The SpaceSaver's compact dimensions make it the correct choice for tiny homes, yurts, small cabins, pool houses, and any installation where a standard-footprint toilet doesn't fit the available bathroom space. The SpaceSaver is certified to Standard 41 with the National Sanitation Foundation. Installations include but are not limited to: cabins, cottages, homes, yurts, pool houses, cabanas, bunkies, camps, treehouses, and workshops. Safety drains should be connected as evaporation capacity is limited by the smaller heater and evaporating surface.

Best for:

• Tiny home, yurt, treehouse, and bunky installations where the standard footprint of the Excel or Compact doesn't fit the available bathroom space — the SpaceSaver's 19-inch width that fits even a converted closet
• Solo occupant or couple seasonal use cabins and cottages where the SpaceSaver's capacity for 1 adult full-time or 3 adults seasonal matches the actual use frequency and population without over-specifying for capacity that won't be used
• Off-grid pool houses, workshops, and outbuilding bathroom installations where a compact composting toilet provides functional sanitation without sewer connection or septic system requirements

Sun-Mar Compact – Mid-Size Self-Contained for Cabins and Cottages

The Compact occupies the mid-size position in Sun-Mar's self-contained lineup — larger capacity than the SpaceSaver and smaller footprint than the Excel, serving cabins, cottages, and residential applications that need more capacity than a single-person unit but don't require the Excel's full residential capacity. The Compact's three-chamber Bio-drum design mirrors the SpaceSaver's composting mechanism at a slightly larger drum size — providing additional capacity headroom for families and seasonal use that the SpaceSaver's single-person residential rating doesn't accommodate. Electrical and Non-Electric (NE) configurations are available — the NE version eliminates the electrical heating element and powered fan for passive composting operation in off-grid locations without power infrastructure. NSF Standard 41 certified.

Best for:

• Seasonal cabin and cottage owners with 2 to 4 adult weekend users who need more capacity than the SpaceSaver's single-person residential rating but don't require the Excel's full 3-adult residential specification
• Off-grid cabin builders who want the Compact NE (Non-Electric) for passive composting without electrical infrastructure — the version that operates entirely without power in remote locations where solar or battery systems aren't yet installed
• Replacement buyers upgrading a failing traditional flush toilet in an existing cabin bathroom where the Compact's dimensions fit standard bathroom rough-in spaces without requiring full bathroom reconstruction

Sun-Mar Centrex 1000, 2000 & 3000 – Central Composting Systems for Full Residential & High-Capacity Use

Sun-Mar's Centrex central composting systems separate the composting drum from the toilet — the composting unit installs remotely (basement, crawlspace, below the floor) and connects through a 3-inch drain pipe to a conventional-looking toilet above. The Centrex 3000 High Capacity Central Composting Toilet System is the largest central composting toilet system in the Sun-Mar lineup — capable of handling a family of 6 full time or up to 9 for part-time seasonal use. When used seasonally by up to 9 adults, compost will normally only need removing annually each spring. Centrex systems allow the use of Sun-Mar's Elongated Airflow (AF) waterless toilet or the AM Style II low-flush toilet above — providing the option of a true waterless system or an ultra-low-flush aesthetic that looks indistinguishable from a conventional bathroom. Centrex 1000 serves smaller households; Centrex 2000 serves medium capacity; Centrex 3000 handles the highest family and commercial capacity.

Best for:

• Full-time residential properties without sewer access or with prohibitive septic installation costs where the Centrex 3000's family-of-6 full-time capacity provides genuine household-scale composting sewage management
• Multi-bathroom cabin and cottage renovations where the appearance of a conventional bathroom above with the composting system below satisfies both aesthetic requirements and off-grid waste management needs
• Property developers and off-grid homesteaders building permanent residences who want the highest-capacity Sun-Mar system with annual compost emptying cycles and the flexibility of toilet choice above the composting unit

Sun-Mar GTG – Urine-Diverting Composting Toilet for Space-Efficient Off-Grid Use

The GTG is Sun-Mar's urine-diverting composting toilet — the smallest Sun-Mar unit, using the urine separation technology that modern composting toilet design has adopted as the standard for odor management in the smallest possible footprint. Urine diversion separates liquid from solid waste at the bowl, directing liquids to a separate container and allowing solids-only composting in the drum — the separation that eliminates the anaerobic decomposition of combined waste that creates odor. The GTG's design serves the most space-limited installations and lowest-use-frequency applications in Sun-Mar's lineup: individual outbuildings, seasonal hunting camps, remote tool sheds, and any installation where minimal footprint and the most accessible price point in the Sun-Mar lineup are the primary selection criteria.

Best for:

• Remote hunting cabins, fishing camps, and seasonal outbuildings where a urine-diverting composting toilet provides functional sanitation at the smallest possible footprint and lowest possible investment for infrequent low-season use
• Off-grid gardeners and homesteaders who want to capture urine separately for diluted garden fertilizer application — the urine diversion that makes the GTG's liquid output directly useful for garden nitrogen without the waste management required for combined sewage
• First composting toilet buyers evaluating the technology at minimal upfront investment before committing to the Excel or Centrex series for a larger installation

Who This Is For

• Off-grid cabin, cottage, and rural property owners in areas where sewer connection isn't available and the cost of a full septic system ($15,000 to $40,000 in many US regions) makes a Sun-Mar composting toilet the economically rational and environmentally superior alternative
• Tiny home, yurt, treehouse, and alternative housing builders who need NSF-certified composting toilets for building permit applications in jurisdictions that require certification documentation for non-sewered waste systems
• Sustainability-focused homeowners and property developers who want to eliminate water-flush sewage from their property entirely — reducing water consumption, eliminating septic maintenance costs, and producing usable compost from the household waste stream
• Seasonal cottage and vacation property owners who spend weekends and summer months at properties without sewer access — the Compact, SpaceSaver, and lower-capacity Sun-Mar models that serve seasonal population without the year-round infrastructure investment of a septic system
• Hunters, fishermen, and remote outdoor enthusiasts building permanent structures at remote land parcels where any sanitation infrastructure requires fully self-contained solutions
• Property owners experiencing septic system failure who need a certified replacement that doesn't require a new drain field installation — the Sun-Mar Centrex system that eliminates the septic entirely

How to Choose the Right Sun-Mar Composting Toilet

Self-contained vs. Centrex central by installation context — Self-contained units (GTG, SpaceSaver, Compact, Excel) contain the entire composting system within the toilet unit — the correct choice for new bathrooms, small cabins, and installations where a below-floor or basement composting drum isn't practical or desired. Centrex central systems require a remote location for the composting drum (basement, crawlspace, or exterior-adjacent space) and allow a conventional-looking toilet above — the correct choice for full-time residential use, multi-bathroom buildings, and situations where the aesthetic of a conventional bathroom matters. If there's no accessible space below or adjacent to the bathroom, self-contained is the correct format.

Electric vs. Non-Electric (NE) by available electrical infrastructure — All Sun-Mar electric models require a 110V AC power connection for the heating element and fan — the electrical components that accelerate composting and handle liquid evaporation. Non-Electric (NE) models operate through passive venting without electrical connections — the correct specification for completely off-grid installations without electrical infrastructure. NE models require more careful ventilation design and may have reduced liquid evaporation capacity — safety drains should be connected on NE models. If reliable 110V power is available, electric models provide better composting performance and greater liquid management capability.

Capacity by occupant count and use frequency — Sun-Mar provides specific capacity ratings for every model in two categories: residential continuous use and seasonal/vacation use. Residential continuous use ratings assume daily use 365 days per year — the most demanding specification. Seasonal use ratings assume weekend and vacation use patterns with lower daily frequency. Always select a model at or above your actual occupant count and use pattern — do not pick a unit that is below your capacity. Under-specifying capacity creates overloaded conditions that produce odor and require more frequent emptying.

Installation space by model dimensions — The SpaceSaver at 19" wide x 22" deep is Sun-Mar's smallest self-contained unit — fitting even a converted closet. The Compact and Excel require standard bathroom rough-in dimensions. Centrex systems require a separate accessible space for the composting drum connected by a 3-inch drain pipe through the floor. Measure the available bathroom space and confirm the specific model's dimensions fit before purchasing — Sun-Mar's product pages list exact dimensions for every model.

Permit documentation requirement by jurisdiction — Some US counties and municipalities require NSF Standard 41 certification for composting toilet permit applications. Sun-Mar's self-contained lineup — Excel, SpaceSaver, Compact — carries this certification. The GTG and Centrex systems' certification status should be confirmed with Sun-Mar directly for specific jurisdictions that require documentation. Contact Sun-Mar at compost@sun-mar.com or 1-888-341-0782 before purchasing if permit compliance documentation is required for your installation.

Frequently Asked Questions

Q: How does a Sun-Mar Bio-drum composting toilet work? A: Sun-Mar's patented Bio-drum is a rotating drum that holds the composting material — the rotating action aerates the material continuously to maintain aerobic conditions that minimize odor and accelerate decomposition. When the user turns the drum handle, fresh waste from the drum receives oxygen exposure while the composting material throughout the drum gets mixed. A heating element in electric models warms the drum interior to accelerate microbial activity; a fan draws air through the drum and out the vent pipe to remove moisture vapor and any residual odors before they reach the bathroom. The Excel's Bio-drum technology was tested by the National Sanitation Foundation at maximum capacity for 6 continuous months, during which it produced no odor and produced clean, safe compost.

Q: How does the Sun-Mar Excel compare to the Compact and SpaceSaver? A: The three models differ primarily in capacity and physical size. The Excel serves 3 adults or a family of 5 for residential use, or 6 adults or a family of 8 for weekend and vacation use — Sun-Mar's largest self-contained model with the highest capacity Bio-drum. The Compact is mid-range — larger capacity than the SpaceSaver at a smaller footprint than the Excel. The SpaceSaver serves 1 adult for residential use or 3 adults for weekend use at dimensions of 19" wide x 22" deep — Sun-Mar's smallest self-contained unit and the correct choice when bathroom space is severely limited. Choose based on occupant count, use frequency, and available installation space — the Excel is the correct choice when capacity is the priority; the SpaceSaver when physical space is the constraint.

Q: Is a Sun-Mar composting toilet NSF certified and does that matter for permits? A: Only Sun-Mar self-contained units are listed for residential and cottage use by NSF, whose Standard 41 is the toughest composting performance standard in the world. NSF Standard 41 certification matters directly for property owners in jurisdictions where local health authorities require certification documentation before issuing a composting toilet installation permit. Sun-Mar's 40-year history as the holder of this certification makes their models the default specification for permit-required installations — competing composting toilet brands without NSF Standard 41 listing may not be acceptable in those jurisdictions. Confirm your specific county and state's requirements before purchasing.

Q: What is the difference between the Centrex 1000, 2000, and 3000? A: The Centrex systems differ in composting capacity for different household sizes. The Centrex 3000 is the largest central composting toilet system in the Sun-Mar lineup — capable of handling a family of 6 full time or up to 9 for part-time seasonal use. When used seasonally by up to 9 adults, compost will normally only need removing annually each spring. The Centrex 1000 serves smaller households; the Centrex 2000 serves medium capacity between the 1000 and 3000. All three Centrex models install the composting drum remotely — in a basement, crawlspace, or accessible space below the toilet — and connect to either a waterless AF toilet or the AM Style II low-flush toilet above. Choose based on the number of full-time or seasonal occupants using the system.

Q: Do Sun-Mar composting toilets require electricity? A: Sun-Mar offers both electric and Non-Electric (NE) versions of most models. Electric versions require a standard 110V AC power connection for the heating element that accelerates composting and the fan that manages odor and liquid evaporation. Non-Electric (NE) versions operate entirely through passive venting without electrical connections — the correct specification for completely off-grid installations. On NE models, evaporation is limited by the smaller heater and evaporating surface, so safety drains should be connected. Electric models provide better composting performance and liquid evaporation management — choose electric when reliable power is available; choose NE only when electrical infrastructure is genuinely unavailable.

Q: How often does a Sun-Mar composting toilet need to be emptied? A: Emptying frequency depends on the model, use intensity, and whether the installation is electric or non-electric. The finishing drawer — the output chamber that receives fully composted material — is the emptying point. For the Excel at full residential capacity of 3 adults, the finishing drawer may need emptying every 3 to 4 months with regular rotation. For the Centrex 3000 at seasonal use of up to 9 adults, compost will normally only need removing annually each spring. Less frequent use and larger capacity systems extend emptying intervals; heavier residential use of smaller-capacity models requires more frequent attention. Sun-Mar's website includes detailed maintenance guides for each model's expected emptying frequency under different use scenarios.

Sun-Mar has been the world standard in composting toilet technology for over 40 years — and the reason the Excel was the first composting toilet NSF Standard 41 certified, and the reason Sun-Mar self-contained units remain the only models listed for residential and cottage use by NSF, is the engineering commitment to a composting process that genuinely works at the capacity levels real households demand. From the GTG urine-diverting entry model through the SpaceSaver, Compact, Excel, and Centrex 1000/2000/3000 central systems, Sun-Mar's lineup covers every off-grid and sustainable property's composting toilet need at every capacity level. Adventure Motion carries the Sun-Mar composting toilet lineup for off-grid cabin builders, tiny home dwellers, cottage owners, and sustainable property developers. Browse the complete Sun-Mar Composting Toilets collection and find the right system for your installation.

For help choosing between Sun-Mar models for your specific property, user count, electrical availability, or permitting requirements — contact the Adventure Motion team and we'll help you select the right unit before your installation begins.

Also explore these related collections: Composting Toilets — The complete composting toilet category including Sun-Mar and other brands for every off-grid, van life, and cabin waste management application. Camping & Outdoor — Outdoor essentials, camp furniture, and adventure gear that complete the off-grid property and outdoor lifestyle that Sun-Mar composting toilets serve.