Q. What do you mean by Manhole loss?
Manholes are provided in locations where there are changes in direction, size and gradient of gravity pipelines. Generally practice for straight pipelines manholes have to be installed at a certain spacing to facilitate the maintenance of pipes. With the introduction of manholes, there are numerous reasons that account for the manhole loss:
(i) Sudden expansion of inflow into manholes and sudden contraction of flow out of manholes lead to major energy losses.
(ii) It isn't uncommon that numerous pipes may be connected to the same manhole. The intermixing of flow takes place inside the manhole and this results in head losses.
(iii)Flow inside the manholes can be designed to change directions that contribute to further losses.