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Rainwater harvesting is a way of saving the rainwater which would normally flow off a roof and down the drain, and using it as piped water to flush toilets and for the garden watering, yard washdown, vehicle and car washing, instead of treated drinking (potable) water.
How does rainwater harvesting work?
A storage tank is fitted to your stormwater drain from your roof, and falling rain enters the tank through a filter which removes leaves and other matter. The storage tank is usually buried under car or vehicle parks, a garden or under the entrance access or drive, and contains a pump which pumps the rainwater to the building where it is piped to the toilets, and to the outside taps.
How much water can a system save?
Depending on your normal usage, it can save 30 to 50% of the treated drinking water from the mains in houses and up to and up to 80% of the treated drinking water in a business or commercial building.
How much would this save on water bills?
Depending on your normal usage, it can save 30 to 50% for the domestic user and 80% for the commercial user of the treated drinking water from the mains. Having metered water is the best way of appreciating the difference.
How much rainwater does a system collect?
This depends on the area and angle of your roof, and your rainfall. Averages of 100,000 litres per household are commonly quoted, much more for large roofed commercial buildings.
What can you use the water for?
Filtered, untreated rainwater should only be used for non- drinking or bathing purposes: toilet flushing, gardens and vehicle or yard wash downs
Is it only for houses?
No, bungalows and commercial premises are also very suitable, the only limitation is the area of the roof to capture rain, compared to the number of users; this puts a limitation on flats and apartments.
Where is it installed?
The tank should be buried under a car or vehicle park, landscaped area, garden, patio or drive, with space left for the round access cover. Most systems are designed so that they can accept cars driving over them if suitably installed.
How much does it cost?
Domestic systems can cost from about £2500 up to £4000 plus including installation costs, depending on size of tank. Commercial systems can cost a lot more depending on size and requirement, but usually have a much quicker 'pay back' period due to the size of roof and high usage
What happens when there is no rain?
When there is a prolonged spell without rain, the water level in the storage tank will fall to a minimum level. At this level, a float switch will open a valve from the normal mains supply and keep the storage tank topped up, until it is filled by rain again. Normal system design should allow up to a week without rain, given normal usage.
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