The term “rainwater harvesting” refers to the process of collecting, storing, and using rainwater as a complementary or alternative source to mains water. A garden water butt is a simple example of a basic rainwater harvesting system, which is used to capture and store rainwater to be later used in a domestic garden.
Harvested rainwater is currently commonly used for washing cars, watering plants and flowers, washing clothes, and flushing toilets.
Direct-Pumped Rainwater Harvesting Systems
As well as water butts, there are several other types of rainwater harvesting systems. These include direct pump (submersible) systems, which are often used in domestic properties and small commercial installations. The pump, located within the underground tank, can help send the water directly to washing machines and toilet cisterns, for example.
In a direct-pumped (suction) system the pump is within the control unit in the property, rather than inside the tank, making it easier for the pump and filter to be cleaned.
Indirect Gravity Systems
In this system, mains water is supplied to the header tank rather than the harvesting tank. The header tank then uses gravity to feed the outlets, and the header tank must be full for the pump to work.
Indirect-Pumped Systems
Similar to an indirect gravity system, an indirect-pumped system doesn’t rely on gravity to feed the outlets, instead using a booster pump to send the pressurized water to the outlets. Due to this, the internal tank can be located at any level in the building in which it is installed.
Gravity Only Systems
This rainwater harvesting system is rarely used. It does not deploy pumps, relying solely on gravity; as such, those committed to energy transition, such as Pierre-Mary Bachelet, know that it’s a very energy-efficient option. The tank needs to be placed higher than the outlets but lower than the gutters.
In-Ground Storage Systems
Most frequently found in regions where rainfall occurs predominantly in one season, in-ground storage systems use electric pumps to send the stored water to the outlets. As the tanks are insulated, the evaporation rate is low compared to other options.
Retention Ponds
Retention ponds collect surface run-off water. Mud or concrete is used to line the bottom of the pond, and the harvested water can be used for irrigation, livestock watering, and groundwater recharge
Take a look at the embedded PDF for information on choosing the best rainwater harvesting system.