A rainwater harvesting system collects and uses rainwater to meet some or all of the water requirements for business or general domestic use.

If correctly dimensioned, it enables cost savings to be made by reducing the amount of drinking water used. Furthermore, the rainwater is not drained away into the sewer system; and therefore incurs no sewer charges. Rainwater can be used for many purposes: flushing toilets, in washing machines or for watering gardens. See Fig.1 Rainwater harvesting system

The use of rainwater harvesting systems also reduces the risk of flooding in many sealed areas with sewerage systems, since an extreme increase in water level as a result of sudden heavy rain can be delayed or completely prevented.

Fig. 1 Rainwater harvesting system: Example of rainwater harvesting

Source: KSB Centrifugal Pump Lexicon, https://www.ksb.com/centrifugal-pump-lexicon/rainwater-harvesting-system/192436/