Irrespective of the complexity, rainwater harvesting systems will have the following 5 basic components:
- Catchment : the surface from which rainwater is collected for storage. This could be a rooftop, a paved flooring surface or a landscaped area. Catchment area is the area of that surface, usually calculated in square metres.
- Gutters and Downtake pipes: lead the water from the catchment surface to the storage tank
- Filters and first flush devices: remove grit, leaves and dirt that the rainwater may transport from the catchment, before the water enters the storage tank. When it rains after a long gap, the rooftops are usually very dirty and the rainwater also carries with it a lot of dissolved air pollutants. A first flush device diverts the water from the first rain so that it does not enter the storage tank.
- Storage tanks: These can be above the ground or below the ground.
- Delivery systems: Piping systems that convey the stored rainwater till the point of end-use. It is not recommended to use harvested rainwater for drinking, cooking and dishwashing unless water quality issues are verified and necessary treatment or purification systems installed.
Figure 2.1: Components of a rainwater harvesting system
Source: Rainwater Harvesting - Trainers’ Manual published by Karnataka Urban Infrastructure Development and Finance Corporation
1Catchment is the surface from which rainwater is collected for storage. This could be a rooftop, a paved flooring surface or a landscaped area