Design and Construction of Sewers Notes

3.1 Sewer and its function: Open and closed channel flow.

3.2 Shapes of sewers: Circular and non-Circular sections (Merits and demerits).

3.3 Sewer materials: Requirements; Types (Salt glazed stoneware, cement concrete, cast iron, vitrified clay, wooden, PVC, CPVC, HDPE).

3.4 Design criteria of sewers:

3.4.1 Specific gravity of wastewater.

3.4.2 Design period and selection criteria.

3.4.3 Minimum and maximum velocities; Self-cleansing velocity.

3.4.4 Sewer size and gradient range.

3.4.5 Hydraulic design of sewers by Manning’s, Chezy’s, and Hazen Williams formulae.

3.4.6 Hydraulic elements of sewers for partial flow condition.

3.4.7 Partial flow diagrams and its significance.

3.4.8 Design of sewers of separate and combined systems.

3.5 Introduction to storm water drainage system.

3.6 Construction of sewer: Desk study; Setting out; Alignment and gradient; Excavation of trench; Timbering of trench; Dewatering of trench; Laying and jointing; Testing of sewer (Straightness, obstruction, water, and air tests); Backfilling of trench; Maintenance.