IS 1742:1972 Part 2 is the Indian Standard (BIS) for drainage (outside buildings) - part 2: foul water drains. This code provides comprehensive guidelines for the design, layout, construction, and maintenance of foul water building drainage systems. It establishes standard practices for pipe sizing, determining gradients to maintain self-cleansing velocities, and the proper placement of manholes and inspection chambers.
Provides guidance on the design and construction of foul water drainage systems outside buildings.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Minimum Self-Cleansing Velocity (Pipes) | 0.6 m/s (for drains up to 300 mm diameter) | 0.75 m/s (for storm sewers at design flow) | BS EN 752 |
| Minimum Gradient Approach | Prescribes minimum gradients based on pipe size (e.g., 1 in 120 for 150mm pipe). | Performance-based: Gradient is calculated to achieve the required self-cleansing velocity. | ASCE MOP 77 / BS EN 752 |
| Minimum Pipe Diameter (Main Line) | 150 mm | 200 mm (8 inches) often recommended for public storm sewers to minimize blockages. | ASCE MOP 77 |
| Manning's 'n' (Smooth Concrete Pipe) | 0.015 | 0.013 (for modern precast concrete) | ASCE MOP 77 |
| Maximum Manhole Spacing (e.g., 200-300mm pipe) | 30 metres | Up to 90-120 metres, depending on access for modern cleaning equipment (jetting/CCTV). | BS EN 752 |
| Design Storm Return Period (Urban) | Not explicitly defined, often taken as 2-5 years in practice. | Typically 1-in-20 to 1-in-30 years for no surcharge, with flood routing checks for 1-in-100 years. | BS EN 752 |