Rainwater Harvesting: Minimum requirements

What BWSSB guidelines say

Rainwater storage (surface tank / underground sump) and ground recharge (RCC precast ring well) of minimum 20 litres / square meter of roof area and a minimum of 10 litres/sqm of paved open space. The open well/recharge well should be 3-metre deep (minimum) with a minimum diameter of 0.9 metres without fillings (aggregates, jelly, sand etc.).

Rainwater can be stored in a tank/sump or used for ground recharge. A combination of the two can be used to achieve the stipulated capacity of ‘X’ litres. (X = Roof area in sqm x 20 + paved open area in sqm x10).

The open well should be of minimum 3ft diameter and 10ft deep. Groundwater recharge should not be attempted in places where the groundwater level is very high, and in spots where hard rock strata exists at shallow depths. A shallow sump could be built or a surface tank installed to store harvested rainwater.

Rainwater from the roof and through a filter should not be allowed directly into a live borewell. The filtered rainwater could be directed to an open well beside the borewell.

In case of a failed or very low yielding borewell, a portion of overflow can be allowed from the tank/sump that collects filtered rainwater from the roof.