Effluent Sewer Design Manual

With an Orenco Sewer, raw sewage flows from a house or business to a watertight underground tank. Only the filtered liquid portion is discharged (by either pump or gravity) to shallow, small-diameter collection lines that follow the contour of the land. Solids remain in the underground tank for passive, natural treatment and only need to be pumped every 10 to 12 years (depending on the number of residents and the tank volume).