The Centrex 3000 AC/DC composting toilet system is a continuous "auto-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 series 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. When used seasonally by up to 8 or 9 adults, compost will normally only need to be removed annually at the beginning of the following season. The Centrex 3000 AC/DC features a 370 watt 120 volt thermostatically controlled heater in a sealed compartment beneath the unit coupled with the standard Sun-Mar 30 watt turbo fan and 2" vent stack. The heating system reduces the amount of effluent from the unit, and the fan removes any fresh odors, ensuring odor-free operation. The Centrex 3000 AC/DC also features a 4" vent stack which may be used to vent the unit when no electricity is present. Included with the unit is a 12 volt 2.4 watt fan that we strongly suggest installing in the vent stack, especially if you need to put a bend in the vent as shown in the diagram. All 3000 series units are supplied with a 1" drain hose which should be connected to the 1" drain at the bottom left of the unit