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This is a rooftop rainwater harvesting calculator which provides you with information about the potential of rainwater harvesting (RWH) for your specific building to avoid water shortage in the summer and become water-sufficient. Most of the rainwater can be collected during the monsoon season and store for later usage. Be part of the ‘Water heroes’ movement in Chennai and start saving water!

This tool is inspired by the effort of Shanta Sheela Nair, known as the water woman in Chennai who made RWH an important solution to cope with Chennai’s recurrent water crisis.

Credits :

1. Daily rainfall data sourced from Indian Meteorological Department (IMD).
2. Actual rainwater collection is assumed at 75% of potential by considering runoff co-efficient, first flush, filter efficiency, etc.
3. The process calculation is based on the urban water balance model and does not take into account the evaporation factor as rainwater collected from the rooftop is assumed to drain directly in the underground sump.
4. The RWH recommendations are based on the highest probability of occurrence over 46 years of historical rainfall data.
5. Underground sump capacity suggested is the optimum size from the given roof and number of residents of the building.
6. Groundwaterrechargewell capacity suggested considered the daily overflow volume from the underground tank.
7. The implementation of rooftop RWH system for household water supply requires a watertreatmentsystem for drinking water and cooking, first flush system, filter chamber, piping and overhead tank.
8. It is advisable to test periodically the quality of rainwater in the underground sump.
9. This tool is for residential buildings, apartments and individual houses with a flat roof.
10. Daily water consumption per person for Chennai varies between 40l/d/c to 135l/d/c.
11. List of RWH Contractors, Entrepreneurs, Agencies, Equipmentsuppliers, Manufacturers and any Organizations listed in this tool are from the public domain information and are not the recommended/endorsed list of their capabilities/authenticity/financial transactions.

1. Supplier info #1
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