A harvest for the world
June 05th 2006 Less than 1% of the water treated by public water systems is used for drinking or cooking. Surely there must be a better way of getting water for the other 99% of the time when it is not crucial to have water at such a high level of purity. The answer may be to use rainwater.
A significant proportion of our water needs can actually be met by collecting and using rain from the roofs of our homes or places of work. This saves money, reduces water demand, reduces the pressure on the environment and makes perfect common sense.
So how does it work?
There are a variety of systems on the market, but the general concept is always the same:
• The rainwater is first collected (usually from the building roof), filtered and then stored
• Water is then pumped either directly to the points of use or to an internal break tank
• If the system runs low on rainwater a mains-water back up unit will guarantee continuous supply feeding mains water into the system
• When it rains again, the system changes automatically back to the rainwater supply
Rainwater is free of charge and can be used for any commercial application where there is a high demand for non-potable water. Typical examples are shopping centres, sports venues, hotels, workplaces, distributions centres (vehicle washing), schools and hospitals.
The capital cost payback period for commercial use can be extremely short, with non-potable, harvested rainwater being substituted for expensive mains water.
In the first a Community Centre in Kent with a 950 sq metre roof was fitted with a 26 000 litre storage tank and associated system components at a cost of £5500; the purpose of the system is to supply washing machines and toilets. With an average annual rainfall of over 700mm, and a water harvest potential of more than 500 000 litres per year, the yearly saving on metered water is more than £1700. This gives a capital cost payback of a little over 3-years. More articles from Rainwater Harvesting Association: | 
