Issues in Hydraulic Design of Sanitary Sewers

Abstract

Various protocols are used in the hydraulic design of sanitary sewers, with key differences related to the assurance of self-cleansing, and the selection of Manning’s n. Analyses reported in this paper show that (1) self-cleansing of sewer pipes should not generally be assessed based on a specified full-flow velocity, (2) the typical Manning’s n values for specified pipe diameters recommended by ASCE are not generally appropriate, and (3) an exact analytic relationship between the minimum self-cleansing slope and the minimum flow rate can replace the empirical relations recommended by ASCE.