| The rainwater harvesting industry is always trying | | | | necessary to run a rainwater harvesting system |
| to find ways of making rainwater harvesting | | | | in a typical family home. In the unlikely event of |
| more practical and economical. Rainwater | | | | the panel not providing enough charge to the |
| harvesting can save between 30% and 50% on | | | | battery, mains electricity is used as backup. |
| mains water consumption, and we are all now | | | | Furthermore, unlike normal chargers, the standby |
| under strong government pressure to do this. | | | | mode of the mains charger takes no current at |
| The Code for Sustainable Homes recommends | | | | all, not even a trickle. |
| rainwater harvesting for its higher target levels | | | | So in such a system, the powerful mains-electric |
| (maximum of 80 litres per day per person) and | | | | pump is replaced by a small 12 volt pump which |
| new Building Reg Part G 17K coming in this April | | | | pumps to 8-10 metres high, enough to feed a |
| will, for the first time, make water consumption | | | | header tank on a two story house. One or more |
| limits a legal requirement in new buildings. | | | | relay pumps, with supplemental solar panels, can |
| Rainwater harvesting does, however, in most | | | | be added for taller buildings. It should be noted |
| circumstances use an electric pump to take the | | | | that this system does not provide enough |
| stored rainwater to where it is needed, and this | | | | pressure for garden sprinkling but gravity fed |
| pump needs power. Steps have already been | | | | irrigation is fine. |
| taken to reduce this pump energy use. There are | | | | For quite a while, solar pump kits have been |
| now specially-designed gravity feed systems | | | | available allowing rainwater to be moved without |
| whereby a rainwater header tank is only refilled | | | | the need for mains electricity and without having |
| when empty rather than every time water is | | | | to turn on and off manually. Water can be |
| drawn. This stops the pump hunting, considerably | | | | moved, for instance, from a low level garden |
| reduces pump activity and, consequently, reduces | | | | collecting tank, or even at the end of a polytunnel |
| energy use. To use solar energy to power the | | | | or greenhouse, to a higher level storage tank. The |
| pump is the next logical step. | | | | applications are numerous in allotments, equestrian |
| A gravity-feed rainwater management system | | | | properties, market gardens and for water |
| can now be powered by a solar panel the size of | | | | features. These kits can supply a drip feed |
| small car windscreen. The solar panel, in | | | | watering system through a header tank (so that |
| combination with a submersible 12 volt pump in | | | | water is available for gravity feed at any time, |
| the main storage tank and a battery ensure | | | | even through a time switch). In more |
| rainwater can be pumped to the rainwater header | | | | sophisticated kits, when the float switch detects |
| tank without any use of mains electricity. Both | | | | water, it starts pumping, then when the header |
| the control mechanism of the system and the | | | | tank is full, it turns the pump off. |
| pump are powered by the battery which is kept | | | | Using solar energy to power the pump is a big |
| topped up in daytime by solar power. Even on a | | | | step forward in making rainwater harvesting an |
| cloudy day, tests show that the most up-to-date | | | | attractive sustainable proposition by saving water |
| solar panels can give six times the charge | | | | while not using extra power to do so. |