Why Rainwater Harvesting?
Rainwater harvesting and recycling has been embraced on mainland Europe for many years now. Recently the lack of water (notably in the South of England) means it is becoming a more attractive proposition in other areas too…
RWH systems are available for a range of uses: – domestic / social housing, supermarkets / shops, hospitals / nursing homes and industrial / commercial… in short, anything where non-potable water is required.
Using collected rainwater that would otherwise be a demand for mains water reduces costs and is kind to the environment. An additional benefit is that these systems divert some of the UK’s annual rainfall away from the sewerage system, thus helping to reduce the flooding risks which have featured so largely in the news lately. Why not combine storm water attenuation with RWH systems?
How does it work?
With RWH it is possible to save in excess of 50% of our daily mains water consumption, but what about the electricity cost of running such a system?
Naturally, this depends on what type of system we may require: – Domestic, Commercial, Education, Industrial. Each system can be set up to use different pumps to match individual flow rates etc. However, take a look at the domestic example below: -
• Five-bedroom, 2-story detached house with 3 WCs in Manchester for example
• Occupancy: 2 adults and 4 children
• Average daily use of potable mains water prior to fitting a RWH system: – between 780 – 900 litres per day (284700 – 328500 litres per year)
• Average daily use of potable mains water with a RWH system: – around 390 – 450 litres per day (a saving of between 142000 – 164000 litres per year)
• Pumping costs are low – a standard domestic submersible pump will pump 60 litres per minute at 18mtrs head which means it only takes 7 minutes to pump 450 litres per day
• United Utilities (the local services supplier) charges £0.18554 per kW/hour at the higher rate (February 2011)
• A 1.1kW domestic pump’s total daily cost based on the above scenario is therefore less than 2 pence per day (£9.12 per year)