The Future For Rainwater Harvesting

Everyone working in the built environment across the UK knows that sustainable development is increasingly at the core of all building projects given the `green light,’ especially the larger commercial new-builds.

As water resource management, from surface run-off, to rainwater harvesting is now a challenge that every Site Manager or Architect has to address during the development process, Lutz Johnen managing director of Aquality Trading & Consulting and Chairman of the UK’s Rainwater Harvesting Association, asks where the industry is heading in the UK.

So where are we with rainwater harvesting in the UK? To put it simply, the UK remains behind other European countries when it comes to adopting these new technologies. But will it be the carrot or the stick that helps move the industry forward?

Here in the UK, some 5000 rainwater harvesting systems are installed last year, which when compared to say Germany, where some 100,000 systems per annum are installed, shows how far behind we are.

Why such a difference? Arguably it comes down to grants and regulation, or rather a lack of both in the UK construction sector. It is interesting to note that although current, and past, UK governments have set up various subsidy schemes for wind and solar power projects, there is currently little hard cash available as an incentive for adding rainwater harvesting technologies, especially in larger commercial, industrial or public buildings.

If the same grants were awarded for choosing to install rainwater harvesting technology as are currently available for home heating (£1250 for a ground heat pump, £950 for a biomass boiler) or solar power (£300 for solar water heating panels), then it is likely that the construction industry as a whole would feel the initial benefits and people in UK would start to think much more seriously about sustainable living.

In the commercial sector, similar action is needed to stimulate new thinking. For example, it is not required that a new public building install rainwater harvesting, so those which choose to do so must weigh up the likely savings from metered water supply against the extra costs involved in construction or refurbishment of large offices, hotels or industrial units.

Maybe the adoption of rainwater harvesting is not high on the political agenda because of the perception that Britain has high levels of rainfall and minimal issues with surface water flooding? Experts claimed that 2007 was an especially bad year for flooding in the UK and treated it as a `one-off.’ However in 2010 we saw water use restrictions introduced in the dry summer across some parts of the UK, whilst 2011 got off to a parched start with 11% less rainfall than average in the opening quarter. Cambridgeshire for example saw just 3.5mm of rain in March 2011 – the lowest since 1929 and officially a drought zone.

Localised water supply, rainfall patterns and flash flood risk are increasingly becoming much harder to predict and the common sense solution is to plan for both dry spells and severe downpours during the planning and construction phases on any new project.

One salient fact from the 2007 floods is well worth noting; two thirds of the 57,000 UK homes affected by flooding suffered that damage via overloaded local drainage systems.

Rainwater harvesting technologies are used in other countries to help manage issues of drought and surface water run-off from a site. Both of these areas are being examined by the UK government but currently any adoption is voluntary, although it is likely that they will become mandatory particularly on larger scale developments where surface water run-off poses a serious issue.

The Government has stated its targets in the UK Code for Sustainable Homes where it calls for a reduction in average consumption from 150 litres of piped water per person, per day, to 80 litres by 2016. When coupled with the SUR1 restrictions on surface water run-off it looks as if some important steps are being taken – although they are largely voluntary on behalf of the developer.

The commercial sector seems to have a larger carrot attached as rainwater harvesting can save substantial sums on the day-to-day facility overheads. Saved rainwater can be used to flush toilets, cleanse urinals, fill washing machines, vehicle power washers, irrigate gardens or even supply a fire sprinkler system. The cost savings in say a typical multi-occupancy office building, where up to 80% of the water used is solely for flushing toilets can be considerable.

Aquality’s work at the Westfield shopping development in London is a good example of this cost-saving strategy and environmental benefit in practice.

In 2005 the Waterman Group looked at the existing plans for rainwater harvesting at Westfield. The goal was to supply all 200 toilets within the facility using harvested water. By taking a joined up approach and using attenuation tanks to store water for use in the building significant savings and efficiencies were achieved.

Severn Trent Water’s Coventry HQ was another showcase project, with water recycling high on the agenda. Mains water supply being used only for drinking water and washing facilities.

Every water appliance in the Severn Trent building needed to be low consumption and instead of a mains piped back up, Severn Trent used a combined borehole, rainwater harvesting and greywater recycling system as a reserve supply for the water harvesting tanks.

The latest figures from the Environmental Agency show how the pressure on developers is likely to increase. By 2050 the UK may have a rise in its population by around 20 million people, which when coupled with a forecast 10% reduction in supply from some key sources, highlights obvious potential shortages.

What needs to happen now is for the government to work its carrot and stick in tandem so people are encouraged to adopt water efficient measures while also being incentivised for doing so.