Manhole Junction Flow

by Jiri Marsalek, Resident Sci.; National Water Research Institute, 867 Lakeshore Dr., Burlington, Ontario, Canada L74 4A6,

Serial Information: Civil Engineering—ASCE, 1987, Vol. 57, Issue 1, Pg. 68-69

Document Type: Feature article


When a sewer surcharges, a basement floods, or sewage overflows, the likeliest source of the problem is sewer junction manholes. Poorly designed ones act as bottlenecks. Study of a few, relatively small residential storm sewer systems suggests that junction losses typically account for 20-30% of total head losses. This article describes two ways to reduce junction head losses—benching and flow smoothing within the manhole, and increasing sewer diameter near the manhole. Optimally designed benching can reduce headlosses about 25%, and enlarged pipe diameter, up to 50%. The article summarizes the report Head Losses at Selected Junction Manholes, published by the American Public Works Assn., Chicago.

Subject Headings: Head loss (fluid mechanics) | Manholes | Basements | Floods | Sewage | Overflow | Storm sewers | Pipelines | Chicago | Illinois | United States

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