Define the following sewage/drainage terms:- (i) Manhole (ii) Benching (iii) Half channel – NABTEB QUESTION

ANSWER:

(i) A manhole is an inspection chamber exceeding 900mm in depth. There are iron steps or ladder built in the manhole wall at 300mm height to provide access into the manhole where the depth is.

(ii) Benching is a weathering construction made at the sides of the invert of a manhole or inspection chamber to control the flow of sewage and to allow a man to stand.

(iii) Half Channel is a pipe cut along its length either in half and used at the internal bottom of the inspection chamber or manhole. It may also be formed with concrete.