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Senior Water Consultant Graham Mann examines the case for rain water harvesting.

Rainwater collection or rain water harvesting as it is better known in the market appears to be gathering pace, up to more recently I was of the opinion paybacks for installation of the rainwater harvesting kit were re-paid over many years, this is not to say some projects are not long paybacks. However, I have examined some case studies provided by one of the leading rainwater harvesting companies StormSaver, they have kindly provided some actual case studies of a selection of projects which I must say overall are producing very attractive paybacks for example: –

A development of multi use with sustainability a priority an integrated approach has enabled an achievement of a BREEAM Excellent rating and ‘A’ energy performance rating. Rainwater harvesting has been included to ensure efficient water usage.

Building 1  – Tray washing –   Water used for tray washing – Collecting from a 12000m² roof area – Massive 168,000 litre tank – 63% efficiency – £ 18,329 financial saving per annum – Payback period just over 1 year.

Building 2 – Office with 31wc’s and 14 urinals – Collecting from a 2150m² roof area – a  20,000 litre tank – 44% efficiency – £ 2,950 financial saving per annum – Payback period 5 years.

Building 3 – Industrial use – Collecting from a 21000m² roof area – Massive 288,000 litre tank – 16% efficiency – £ 32,501 financial saving per annum – Payback period 1 year.

Case study North Chadderton Academy.

The above ground rainwater harvesting system is one of the many sustainable aspects that were incorporated within the part re-build and part remodel of the existing school premises. The system is also connected to an interactive BMS system which has the capability to convert consumption to costs and provide out of profile alarms for all systems. The system is super-efficient and should have paid for itself in les than three years!.

Statistics – Collecting from a 8143m² roof area – 50,000 litre above ground tank – potential rainfall collection 2,817,000 litres per annum – non pressurised system – BMS monitoring – 75% efficiency – £ 6,450 financial saving per annum – payback period 2.5 years.

In both of the above case studies the paybacks are pretty attractive, much is dependant I guess on the amount of water collected, however rainfall is increasing substantially which will reduce payback periods with water and waste water charges increasing and technology improving in leaps and bounds within the rainwater harvesting industry it is now well worth a feasibility study.

There is money available through environmental investment companies for projects of this nature.

Thank you to StormSaver for providing the case studies.

Feedback on this story is welcomed and much appreciated.