Rooftop Rain Water Harvesting

Rooftop rainwater harvesting involves collection of water from the roof and storing it for potable or non potable use.

The rooftop rainwater harvesting has 3 main components.

1. The piping or gutter system

This is the conduit mechanism for transmission of water from rooftop to the collection via a pre filter and a filter. Different pipe Cross-sections and gauges are used depending on the catchment area, height of the building and pressure requirements. Gutters are provided in case of sloped buildings.

2. Pre filter or First rain separator

First rain separator or FRS is a piping arrangement to segregate the first few minutes of water during every rain. By this arrangement, it is ensured that the rooftop (catchment) is washed in every rain. The dust particles collect in the bottom of the FRS which can be flushed out manually or automatically. The FRS also acts as a by-pass arrangement. In case there is a catchment maintenance or if rainwater is not required for some reason, the water can be let out by opening the FRS.

3. Filter

When the catchment /Rooftop is clean and if the FRS is maintained well, there is hardly any contamination in the water. However, for separating physical contamination of the next order, a filter is recommended.

Two types of filter are used.

Modified sand filter

This is the most conventional and time tested filter. It contains 3 layers of graded metal and raw charcoal in a designed proportion (Sometimes Activated carbon is also used). Each layer is separated by a nylon mesh. The graded metal is used to sieve the particles. The dirt particles get trapped in the pores between the metal. A layer of charcoal is provided to adsorb any gas or smell in the water. The minute pores in the charcoal section also help in trapping fine dust. These filters can be built on the ground or can be underground as well.

Cartridge filters

These are wall mountable modern day filters. Many modules of cartridge filters are available. Most cartridge filters work on swirling mechanism of water. During the swirling movement of water inside the cartridge, the heavy particles and dust are thrown out and the relatively clear water flows into the collection tank.

After the water has passed through the filter it is directed towards the underground tank for daily usage .

For more Information, watch the below video.