Making hay when the sun doesn’t shine
March 04th 2008

The use of rainwater for non-potable applications in commerce and industry not only saves the cost of purchasing high-grade drinking water when it’s not needed but also it reduces sewerage costs and the strain of the drainage system that can lead to flooding in times of heavy rainfall

There are about 326 million trillion gallons of water in the world. 97.5% of it is salt water, leaving a mere 8.15 million trillion gallons (2.5%) as fresh water. Although North America, Europe and Russia are unlikely to see a serious threat to water supply by 2025, most of the rest of the world will see some kind of shortage. Even in a stereotypically soggy country like the UK supplies are no longer guaranteed, largely because the rainfall has become unreliable.

In 2007 UK rainfall in June was 202% of the same month in 2004 - 2006, and July was 226% compared to the same period. August 2007 was 79% of the 2004 - 2006 figure; September was 67% and October just 53% – one of the driest autumn’s on record.This is particularly stark in the south of England, where the water available per capita is already less than that of many Mediterranean and Middle East countries.

The growth of the UK population will add further pressure to water supplies – from 60 million people in 2006, the Office for National Statistics predicts 63 million by 2011 and 71 million by 2030.

Environment Agency field trials have shown that while a domestic rainwater harvesting system can reduce consumption by around 50%, the saving can be as much as 80% in office blocks and commercial buildings with a large roof area and a high demand for water for things like flushing toilets or washing fleets of vehicles.

For every 100 m2 of roof area around 75,000 litres of water can be harvested each year, and under the ‘enhanced capital allowance’ scheme business owners can claim 100% tax relief for rainwater harvesting systems on the Water Technology List.Unfortunately, too few buildings in the UK have systems installed each year to allow for cheaper ‘bulk buying’ prices like those in Germany, where the rainwater harvesting market is 300 times that of the UK.

That said, the UK market for rainwater harvesting systems has tripled in the last 2 years, with a further 100% or more growth forecast for next year. This is a trend likely to continue, given the Governments review of national water management policy, and the support given to rainwater harvesting in the recent report of the House of Lords Science & Technology Committee.

Today rainwater is often considered a flood risk issue,but rainwater harvesting aims to change this by persuading businesses that retaining the water for non-potable use can make it an asset not a problem.Rainwater is free, the systems can pay for themselves in a few as three years and can be used for any commercial application where there is a high demand for non-potable water. The steady increase of industrial uptake in systems suggests that UK PLC is finally catching on.

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