Testing of sewer pipes may involve
Manholes are generally located
When a sewer line is dropped below the hydraulic gradient line to pass it through an obstruction, the arrangement is known as
An inverted siphon is a sewer section constructed lower than the adjacent sewer sections, and it runs full under gravity with pressure greater than the atmosphere. An inverted siphon is usually made of siphon tubes or pipes made of cast iron or concrete.
The slope of a 1.0 m diameter concrete sewer laid at a slope of 1 in 1000, develops a velocity of 1 m/s, when flowing full. When it is flowing half-full, the velocity of flow through the sewer will be
For d/D = 0.5; v/V = 1.0
where d is depth of flow
v is flow velocity at depth d
D is diameter of sewer
V is flow velocity at full flow
∴ v = 1.0 m/s
Self-cleansing velocity is
In the design of storm sewers, “time of concentration” is relevant to determine the
Time of concentration (tc) is the time taken by water droplet to reach the catchment outlet from farthest part. So whole catchment contributes to runoff only when the time of rainfall is greater than 'tc' it is used to determine critical rainfall intensity.
The maximum flow occurs in an egg shaped sewer when the ratio of flow depth to vertical diameter is
Match List-I (Unit) with List-ll (Purpose) and select the correct answer using the codes given below the lists:
A. Leaping weir
B. Gutter inlet
C. Inverted syphon
D. Catch basin
1. To prevent grit, sand, debris, etc. from entering the storm sewer.
2. To carry the sewer below a stream or railway line
3. To drain rain water from roads to the storm sewer
4. To 'separate storm water and the sanitary sewage
A B C D
(a) 4 3 1 2
(b) 4 3 2 1
(c) 3 4 2 1
(d) 3 4 1 2
A sewer is commonly designed to attain self- cleansing velocity at
If a sewer X is to be designed to generate equivalent self-cleansing action as in sewer Y, then
Velocity and discharge are functions of tractive force intensity which depends upon friction coefficient as well as flow velocity. For equal self cleansing tractive force intensity should be same in both sewers.