The Centrex 2000 A/F NE (Air Flow Non-Electric) is designed for use with a Sun-Mar Dry Toilet (purchased separately). This unit is ideal for those who do not have water, but still want the composting action to take place outside of the bathroom area. The Centrex 2000 A/F NE is the non-electric version of the Centrex 2000 AF, and is fitted with a 4" vent stack. Installation of a 12 Volt fan is required on this model, and one is included in the box. The Centrex 2000 A/F NE is supplied with a 29½" pipe piece (10" diameter). This is long enough if the floor of the bathroom is up to 38" above the surface that the composter is placed on. The pipe piece can be cut to size and additional pieces ordered if necessary. With the lower evaporating capacity that comes with the lack of an electric heater, the overflow drain should be installed with this unit as there will be overflow liquid. Please click here for more information on handling excess liquid