Sun-Mar Centrex Central Composting Toilet System

Unlike self-contained units like the Excel, Sun-Mar Centrex systems are central composting toilets. The composting chamber (Centrex unit) is installed in a basement, crawl space, or outside, and connects via a toilet flange to a separate bathroom toilet unit like the Sun-Mar Sealand or Ultra-Low Flush toilet.

There are three main Centrex sizes:

• Centrex 1000 Series – Designed for seasonal or light use. Compact size, ideal for 1–2 people part-time. Uses a smaller Bio-Drum™ and evaporative tray.
• Centrex 2000 Series – Mid-size, suitable for 3–5 people full-time or 6–8 part-time. Uses a larger Bio-Drum™ and evaporating tray. Available in Electric (2000), Non-Electric (2000 NE), and AC/DC versions.
• Centrex 3000 Series – Largest system for 6–8 people full-time or 10+ part-time. Offers larger composting volume and evaporation surface. Ideal for large families, retreats, or lodges. Also comes in Electric, NE, and AC/DC.

Electric models include a heating element and fan for maximum composting speed and evaporation. Ideal if you have reliable power.

Non-Electric (NE) models use a 4" vent stack and rely on natural draft (no fan or heater), making them ideal for off-grid cabins or solar setups.

AC/DC models include both 110V power and a 12V fan, allowing you to switch between electric and off-grid/solar as needed.

Here's a quick guide:

• Centrex 1000 – Weekend cabin or seasonal use (1–2 people)
• Centrex 2000 – Full-time small household (up to 5 people)
• Centrex 3000 – Large family, retreat center, or full-time home (up to 8 people)

If you’re fully off-grid, choose the NE or AC/DC versions.

No. Centrex systems are designed to be completely odor-free. Electric models use a small fan to draw air up through the vent stack continuously, while NE models use natural draft. Proper installation of the vent is key to eliminating odor.

You’ll need a compatible Sun-Mar Ultra-Low Flush Toilet or a Sealand 510 Plus toilet. These are specifically designed for central composting systems and use very little water. A traditional toilet will not work with Centrex composting units.

Yes! The Centrex 2000 and 3000 systems can be connected to multiple toilet bowls if properly plumbed. You’ll just want to make sure your model can handle the user load. We’re happy to help size your system—just reach out!

This depends on the model and usage. For full-time families, the solids bin may need to be emptied every few months. The compost drawer makes this a simple process. Liquid is evaporated or drained off.

Sun-Mar Centrex systems are NSF/ANSI Standard 41 certified and legal in many jurisdictions. We recommend checking with your local health or building department for approval before purchasing.