The Nautilus Earthship System Gene showed a video of Michael Reynolds' Nautilus Earthship. The Taos structure is unorthodox for an Earthship in that it is not buried at all. Its rear walls are built of tires, with straw bales on the outside and stucco over all. Gravity feeds the water to a pump, then to filters, and finally to a pressure tank. At this point the water system operates exactly like its conventional counterpart with typical fixtures, vents, and traps.
Water is heated by solar and on-demand gas heaters.
Once the water runs down the drain, everything changes. The bulk of water treatment is carried on indoors so that the system can work year-round. A filter strains out grease and particles. The planter itself is 2.5 feet deep and filled with topsoil over pumice. Bacteria in the pumice eat bacteria in the water and help clean it up.