IS 14961:2001 is the Indian Standard (BIS) for guidelines for rain water harvesting in hilly areas by roof water collection system. This standard provides guidelines for planning, designing, and implementing roof water collection systems for rainwater harvesting in hilly areas. It covers aspects like estimating rainfall runoff from roofs, sizing of system components like gutters and tanks, and maintaining water quality for domestic use.
Guidelines for Rain Water Harvesting in Hilly Areas by Roof Water Collection System
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| First Flush Diversion Criteria | Qualitative: Recommends diverting first 10-20 minutes of rain, often interpreted as 0.5-1.0 mm of rainfall. | Quantitative: Recommends diverting 0.02 gallons per sq. ft. of catchment area (approx. 0.8 L/m² or 0.8 mm of rainfall). | ARCSA/ASPE/ICC 805-2022 |
| Runoff Coefficient (Smooth Tile Roof) | 0.8 - 0.9 | 0.9 (for pitched tiled roofs) | BS EN 16941-1:2018 |
| Runoff Coefficient (Metal Sheet Roof) | 0.7 - 0.9 (for GI Sheets) | 0.9 - 0.95 | ARCSA/ASPE/ICC 805-2022 |
| Water Requirement for Sizing (Potable) | Prescriptive: 10 litres per capita per day (lpcd) for drinking & cooking. | Performance-based: Designer to determine demand based on intended use and local occupancy data; no prescribed value. | ARCSA/ASPE/ICC 805-2022 |
| Tank Inlet Design | Inlet pipe above maximum water level, fitted with a screen. | Specifies a 'calmed inlet' to deliver water to the bottom of the tank without disturbing sediment. | DIN 1989-1:2002-04 |
| Mains Water Top-up Safety | Not explicitly detailed. | Mandates a physical air gap (Type AA or AB per EN 1717) to prevent backflow into the public water supply. | BS EN 16941-1:2018 |
| Tank Overflow Mesh Size | Recommends wire mesh to prevent mosquito entry. | Specifies corrosion-resistant screen with openings no larger than 1/16 inch (1.6 mm). | ARCSA/ASPE/ICC 805-2022 |