21. Water Efficiency - NEW SECTION

There is widespread agreement across governments, water companies and the water industry regulators that concerted action needs to be taken to conserve potable water. Action is needed to minimise water abstraction from rivers and other water bodies; to protect the environment; reduce energy-related carbon use and to ensure adequate water supplies. Current estimates of water availability compared with projected use in 2050, paint an alarming picture with a shortfall predicted by DEfRA of some 5 million litres per day. The inadequacy of our infrastructure is already impacting growth in key areas where housing is needed, such as North Sussex, Cambridge and East Anglia. In the case of North Sussex the progress of the Local Plan towards adoption has been halted by Environment Agency concerns regarding the impact of water abstraction.  

For housebuilders there are serious implications. Firstly, they must navigate a credits scheme that offers discounts on infrastructure charges given by water companies to developers who provide accurate water efficiency calculations for sustainable water use, based on the method in Approved Document G Sanitation, hot water safety and water efficiency (ADG). The regulations also permit planning authorities to set higher standards through planning conditions. Secondly, a progressive reduction in household water use for new homes will mean that greater water saving measures will likely need to be introduced at five-year intervals to 2035.  

The water efficiency requirement in ADG follows either a ‘fittings’ or ‘calculations’ approach and this is likely to continue, with the fittings approach being based on Minimum Water Efficiency Labelling (MWEL), and the calculations revised as recommended by a Future Homes Hub (FHH) working group in their water efficiency road map. A balanced view that also influences consumer behaviour and looks at the wider infrastructural issues (methods of extraction, control of leakage and water recycling) is needed. The new technologies that are emerging for aerated devices and air-assisted WCs, which feature in the FHH roadmap, will need to be appraised in a wider context, for instance their interaction with the sizing of drains in the surface water and sewerage infrastructure in our streets and the wider issues to do with consumer acceptance.   

A recurring concern for housebuilders is the acceptance of low-flow devices and their customers’ expectations for comfort and enjoyment. This is reasonable: nobody would expect a shower in a new home to have the trickle of water that they associate with an outdated electric shower. Even the new generation of electric showers, which have inherently low flow rates and energy consumption, are increasingly being superseded by power showers and mixer showers. 

A variety of water efficient showerhead devices are becoming available in the UK market. In particular, low volume showerheads that use air entrainment or atomising methods to reduce the water flow rate and are claimed to provide a very comfortable shower experience. 

Factors influencing perceived comfort are temperature consistency, spray force (flow rate for non-aerated showers), spray pattern and soap removal. Some manufacturers have taken the initiative in achieving independent verification of energy performance and water consumption from organisations such as the Energy Saving Trust. However, the method for achieving recognition in the Government’s energy calculator used for compliance with Part L, the Standard Assessment Procedure (SAP) is time consuming and costly. Meanwhile, to help establish a level playing field, the industry is lobbying for standards that can assure consumer performance based on metrics such as spray force and spray coverage. 

Things that can go wrong:

• Dual-flush WCs not being operated as intended, or providing inadequate flushing; 

• Manufacturers taking recognition in SAP/HEM as demonstrating that system performance meets all other testing standards; 

• Customer expectations. 

Future-proofing recommendations:

• DESIGN: Specify fittings to meet water saving and comfort expectations; 
• MAINTAIN: DEFRA have also proposed measures in order to ensure WCs don’t waste water when they malfunction (e.g. faulty flush valve seals and design of dual flush systems).