(1) All sewers, other than cast-iron sewers, having less than 300 millimetres clear cover over the socket of the pipe shall be adequately protected by encasing in concrete not less than 100 millimetres thick, having a composition not inferior to 50 kilograms of cement to 100 cubic decimetres of fine aggregate to 200 cubic decimetres of coarse aggregate, Grade 10.

(2) Where, in the opinion of the local authority, sewer-pipes may be damaged by vibration or external pressure, they shall also be encased in similar concrete.