Rainwater Harvesting Pit

Roof-top rainwater recharge pits: annual yield, peak inflow and pit size.

CGWB, IS 15797

Open Rainwater Harvesting Pit

Open it at /civiltechstudio/rainwater-pit/app. Status: live.

Quick start

Size a rooftop recharge pit for a 120 m² roof in a 1,000 mm/yr rainfall area, on soil that infiltrates 25 mm/hr.

  1. Under Design Code / Country, select India (CGWB / IS 15797).
  2. In Catchment, enter Roof area 120 m², Annual rainfall 1000 mm and Runoff coefficient 0.85.
  3. In Storm & Soil, enter Peak rain intensity 50 mm/hr, Soil infiltration rate 25 mm/hr and Storage buffer 30 min.
  4. In Pit Geometry, enter Pit depth 2 m and Filter media porosity 0.4. Leave Count base infiltration (CGWB manual) unticked.
  5. Select Size Pit.

Codes and standards

  • CGWB recharge guidance, IS 15797, rational method (Q = C·i·A)

Inputs

  • Roof area, rainfall, runoff coefficient, soil infiltration rate, pit depth, storage time, fill porosity.

Outputs and exports

  • Annual harvestable volume, peak inflow, pit dimensions, infiltration check.
  • Exports: PDF and Excel report.

Limits

  • Sizing follows CGWB guidance whichever country is selected.