According to IS 1742 : 1983, in the design of gravity drains for building drainage under ruling gradient, the minimum self cleansing velocity and the maximum velocity of flow to be adopted are respectively:
1
0.3 m/s and 1.5 m/s
2
1.0 m/s and 3.8 m/s
3
0.75 m/s and 2.4 m/s
4
0.5 m/s and 3.2 m/s