Collection of rainwater for usage in water systems independently from the main water system. One of the most popular usage of it is in irrigation systems as its natural composition is ideal for watering plants.

Rainwater is collected in underground or rarely oveground tanks on a gravity way so for doing that a separate collection pipework needs to be installed around the house. Retrospective installation of a rain harvesting system can be very costly because of strict levelling, avoidance of existing structures and service supplies around the house.

Return side when the collection surfaces are quite large and a good-size harvesting tank can be installed with minimal effort, the rain harvesting can be an alternative to main water irrigation.