Each change of a flow parameter or of the sewer geometry requires a manhole. If no changes occur, a manhole is needed after about 100 sewer diameters for inspection and rehabilitation purposes. In this chapter, the latter type of standard manhole is described, whereas the following two chapters refer to special manholes.
The recommended standard manhole is characterized by benches up to the pipe vertex, to obtain completely guided flow across the manhole. The manhole flow for both free surface and pressurized flows is described and loss coefficients in terms of manhole geometry are specified for pressurized manhole flow. The choking features of manhole flow are also considered.