Design of Small-Diameter Variable-Grade Gravity Sewers

摘要

An Alabama community uses modified septic tanks to produce clarified effluent that is transported in small plastic lines to a lagoon. Variable-grade gravity sewers as small as 2 inches in diameter transport effluent almost 1,000 feet without problems. The sewers were installed following the profile of the land, without manholes and for less than $2 per linear foot. Cost per family for the complete system (tanks, sewers, and lagoon) was comparable to the drainfield systems. This report describes a successful application of the concept of variable-grade gravity sewers and provides engineering guidance for the design and installation of similar systems.