This code lays down the design, layout, construction, and maintenance guidelines for surface water drains and sewage systems outside buildings. It details the requirements for pipe sizing, gradients, manholes, and the hydraulic principles needed to ensure self-cleansing flow.
Provides guidance on the design and construction of surface water drainage systems outside buildings.
Quick Reference Values
Minimum diameter of domestic drain pipe100 mm
Minimum diameter of public sewer150 mm
Gradient for 100 mm diameter pipe1 in 60
Gradient for 150 mm diameter pipe1 in 100
Maximum manhole spacing for pipes up to 0.9m diameter30 m
Minimum concrete cover for pipes under roads150 mm all around
Key Formulas
Q = A * V — Continuity Equation for flow
V = (1/n) * R^(2/3) * S^(1/2) — Manning's formula for pipe flow
Practical Notes
Drains should strictly not pass under a building. If unavoidable, use cast iron pipes with mechanical joints or completely encase the pipe in reinforced concrete.
Always provide a manhole or inspection chamber at every change of alignment, gradient, or diameter.
Ensure pipes are laid to appropriate gradients to maintain self-cleansing velocities and prevent siltation.