Neil Smith, Group Research and Innovation Manager, NHBC, said “While grey water recycling and rainwater harvesting systems can reduce domestic water consumption, they can also lead to increased energy use and carbon emissions.

“New homes built to current building regulations already deliver a much better level of water efficiency than existing homes. Therefore, from an overall perspective of saving water in a simple and affordable way, installing water meters in more existing homes would have a far greater impact on reducing overall consumption without these unintended consequences than additional measures in the relatively small number of new homes.”

New homes are currently built to comply with water use targets set out in Part G of the building regulations, which specifies a limit of 125 litres per person per day – and deliver significant water savings well in excess of the UK average consumption of 150 litres per person per day. In addition, water metering is standard in new homes, whereas only about 40%* of existing homes have one fitted.

Although further improvement to the water efficiency of homes can be gained through grey water recycling (the re-use of bath and shower water) and rainwater harvesting – normally for flushing toilets – there are broader environmental issues that need to be taken into account. A study undertaken by the Environment Agency, the Energy Saving Trust and NHBC Foundation in 2010, Energy and carbon Implications of rainwater harvesting and greywater recycling, demonstrated that these systems can increase energy use and carbon dioxide emissions due to the energy used in their manufacture, installation, operation and maintenance.