Section 6(c) in The Chennai Metropolitan Water Supply and Sewerage Board's Sewerage Regulations, 1988
(c)(i)The sewer shall be of adequate size. - In no case shall it have an internal diameter of less then 100 mm nor more than such size as may be necessary for the flow or as may be approved.(ii)The standard gradient for the sewer shall normally be 1 in 40 for 100 mm diameter and 1 in 80 for 150 mm diameter sewer.(iii)Missing.(iv)Every change of direction should be formed by properly curved pipes or channels with means by building a manhole at the change point. Manholes shall have side walls with brick in Cement Mortar 1:3 to a minimum of 23 cm thickness and foundation with concrete 1:3:6 for a minimum thickness of 15 cm and with an inter opening of 45 cm square(v)Stoneware pipes with socket spigot joints shall be joined using cement mortar with 1 part cement and two parts of sand measured by volume over initial packing with spun yam soaked in tar or cement and caulked.(vi)Every pipe shall be securely bedded on firm ground and filled round with selected material free from large stones, watered and well rammed into place. Where any sewer traverses softer yielding ground or where subsoil water is met with such sewer shall in addition, be bedded in or completely encased with concrete to a minimum thickness of 130 mm.(vii)Every sewer line be tested to a hydrostatic pressure heed of 1.5 m of water over the highest point of the sewer. The sewer shall show no signs of leaking or oozing after the pressure has been maintained continuously for 1 hour and no pipe shall be covered up until it passed this test to the satisfaction of the authority.(viii)Bends and junctions shall be grouped together and wherever possible provided with means of access by building manholes around them.(ix)All fittings shall be placed on a bed of concrete for a minimum thickness of 100mm.(x)The terminal manhole of the sewer within the premises shall have benching and channelling so done as to connect to the Board's sewer obliquely in the direction of flow of the Board's sewer and avoid any right angled junctions either vertical or horizontal.(xi)No sewer shall be laid under a building, but wherever inevitable, shall be laid in a straight line for whole stretch with cast iron pipes properly joined with lead. If the authorised authority permits, stoneware pipes encased all round with cement concrete to a minimum of 150 mm may be used.(xii)Wherever a sewer is laid across a water main of line, it shall be provided with encasing by concrete as in sub-clause (xi) above.
