Question

As per Manual on Sewerage and Sewage Treatment, Central Public Health and Environmental Engineering Organization, Ministry of Urban Development, Government of India, when a sewer connects with another sewer having a difference of 600 mm in level between the water lines (peak flow levels) of main line and the invert of branch line, the connection may be provided using a
1. Side entrance manhole
2. Junction manhole
3. Flushing manhole
4. Drop manhole

Answer 1

Correct Answer - Option 4 : Drop manhole

Concept:

As per Manual on Sewerage and Sewage Treatment, CHAPTER 3, 2013, the vertical drop may be provided only when the difference between the elevations is more than 60 cm, below which it can be avoided by adjusting the slope in the channel and in the manhole connecting the two inverts.

Important Point:

According to depth, the manholes are classified as shallow manholes, normal manholes, and deep manholes.

Shallow manhole: It is about 700 mm to 900 mm in depth and it is constructed at the beginning of branch sewer or at places which are not subject to heavy traffic. It is also known as an inspection chamber.

Medium manhole: It is about 900 mm to 1500 mm in depth and it is constructed of 1000 mm × 1000 mm or 800 mm × 1000 mm size.

Deep Manhole: It has a depth of more than 1500 mm.