Pilot schemes show rainwater harvesting could yield significant savings in a country where the resource is both reliable and plentiful

By 2018 it is expected that water conservation initiatives and rainwater harvesting will reduce per capita water consumption from the current daily levels of 147.17l/hd to 82.75l/hd, representing 44% potential savings as compared to 1997.

In order to further evaluate the implications of installing rainwater harvesting devices, the Department of Environment commissioned two pilot schemes on which the Dublin Institute of Technology is conducting the research.

Rainwater harvesting clearly has a great role to play, both in initial design
stages and as a retrofit option. Payback times vary according to size, type and metering costs but typically six years is regarded as a reasonable break-even for a 2,000 litre tank in a four-bedroom house.

Basic water recovery systems without filtration can even get a payback time of one to two years while larger scale filtration
systems can take 10 years. In the United States rainwater harvesting was found in some instances to actually be a lower cost option than connecting to the mains.

The Pentagon installed such a system for that very reason. Connecting to themains would have required hand digging 200 feet of trench
over other utility lines buried under asphalt.

Other benefits include reduced storm water runoff from the roof, and
are maximised when used in conjunction with other renewable energy systems such as photovoltaics. In the Pentagon’s case the PV system
provides automatic pumping for the evaporative cooling stages and drain
down of the storage tank for winter freeze protection.

Some initiatives include innovative applications as well. For instance Harvard University uses rainwater to clean as many as 250 University-owned vehicles a week in a bid to reduce pollutant loading into the river. The system basically reduces the runoff from the nearby river, saving 25,000 gallons of water a year.

Rainwater runoff carries pollutants into the river and by harvesting it at the source, the river was found to be less affected. The first DIT pilot project is agricultural and is located in a farm in Clonalvy, County Meath.

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