A 350 mm diameter sewer is to flow at 0.35 m depth on a grade ensuring a self-cleansing equivalent to that obtained at full depth at a velocity of 0.8 m/sec. (n = 0.014)
Proportionate area = 0.31, proportionate wetted perimeter = 0.47
Proportionate hydraulic mean depth (r/R) = 0.77
1
Required grade of sewer is 4.2 × 10-1
2
Velocity generated is 0.765 m/sec
3
Required grade of sewer is 4.2 × 10-3
4
Velocity generated is 0.765 m/min