Sun-Mar Centrex 3000 Composting ToiletThe CENTREX 3000 composting toilet is unique among the Sun Mars Central units. It utilizes a continuous flow design for very heavy cottage or medium residential use. With a continuous flow system, rotation of the drum moves compost along the larger and longer CENTREX 3000 drum, before it drops automatically into the collection housing at the end of the unit. Under normal operating conditions, the drum will not have to be turned backwards for emptying.