Should we cater for manhole loss in design?

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Manholes are provided in locations where there are changes in size, direction and gradient of gravity pipelines. In normal 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 various reasons which account for the manhole loss:

(i) The sudden expansion of inflow into manholes and the sudden contraction of flow out of manholes lead to significant energy losses.

(ii) It is not uncommon that several pipes may be connected to the same manhole. As such, the intermixing of flow takes place inside the manhole and this leads to head losses.

(iii) Flow inside the manholes may be designed to change directions which contribute to additional losses.


This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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