Harvesting rainwater helps conserve our most precious of natural resources: water. Why use drinking water to flush your toilets, wash your clothes or water the garden?
Systems are sized based on the roof area and estimated annual rainfall combined with the likely demand. Typically, the rainwater is stored in a tank buried in the garden. A pump then transfers it when required directly to the toilet or washing machine, or into a storage tank in the loft. A loft tank uses gravity to generate the pressure, so a higher pressure can be delivered for garden hoses etc with a directly pumped system.
Rainwater harvesting is simply collecting rain which falls onto roofs, then storing it and using it as a free resource.
Rainwater Harvesting Systems can be very simple such as a water butt located under a down pipe from your guttering that you use to fill a watering can or connect to an inexpensive syphon hose to water your garden.
At the other end of the scale these systems have large above or underground tanks, filters and pumps which will not only feed to your garden irrigation and car wash but also into all the non-potable uses inside your home such as toilets, washing machines and showers/baths.
Some of the larger systems even have PV panels to generate the power to drive the pumping and water management systems that ensure that the system is topped up by mains water when rainwater is scarce.
These systems can be subdivided into two types; Header Tank Systems and Direct Pump Systems.
Header Tank Systems as the name suggests require a header tank to be installed in the loft, have a high reliability, can easily revert to mains supply if rainwater is scarce and the control system is simple and inexpensive. However the pressure may be too low for some washing machines and flush toilets may take a while to fill.
Most commercially available systems are Direct Pump Systems that do not require a loft tank and generate a good pressure suitable for washing machines that are used to the pressure from a direct
Rainwater recycling involves collecting rainwater from a building’s roof or from any other surface, including nowadays permeable pavements and garden lawns. The rainwater then passes through a filter, which eliminates debris, and is stored in a holding tank placed either underground or the side of a building or in the loft.
This saved water can be pumped to places where it is needed. Since the water collected by most rainwater harvesting systems in the UK is not drinkable (without treatment), plumbing regulations dictate that the collected rainwater be passed through a dedicated pipe system, and not the building’s drinking water system.