This standard provides guidelines for planning, designing, constructing, and maintaining rainwater harvesting (RWH) systems. It covers various components like catchment, conveyance, filtration, and storage/recharge, aiming to promote sustainable water management for both new and existing buildings.
Provides general guidelines for the design, construction, and maintenance of rainwater harvesting systems.
Quick Reference Values
Runoff coefficient for concrete/tiled roof0.80 - 0.95
Runoff coefficient for paved areas (bitumen/concrete)0.70 - 0.85
Runoff coefficient for lawns (sandy soil, <2% slope)0.05 - 0.10
Recommended first flush diversion volume0.5 to 1.0 mm of rainfall
Typical filtration rate for slow sand filters100 - 200 litres/hour/sq.m
Key Formulas
Harvestable Rainwater (m³) = Catchment Area (m²) × Rainfall Depth (m) × Runoff Coefficient
Practical Notes
Always install and maintain a 'first flush' device to prevent the initial, more contaminated runoff from entering the storage tank.
The runoff coefficient is the most critical variable in calculating harvestable water; choose it carefully based on the actual surface material and slope from Table 1.
Regularly clean catchment surfaces, gutters, and filters, especially before the monsoon season, to ensure good water quality and system efficiency.