20 December 2024

A credible approach to making new development more water resilient, but what will it cost to install?

With 5 billion litres of extra water per day needed in England by 2050, there is a need for a wide range of solutions. New reservoirs and leakage reductions, yes, but also measures like water reuse. The Enabling Water Smart Communities (EWSC) project has just released a report exploring the costs of water reuse installations for greywater and stormwater reuse, at community scale and for individual plots.

Water reuse at the property and community scale in the UK remains something of a niche approach. There therefore isn’t much evidence to show what the costs of installing the necessary equipment and pipework might be. We are not aware of any similar study being done on these shores in recent years.

Water reuse in new housing: Understanding the business case presents the capital costs for external pipework, storage and treatment equipment, and internal pipework. These costs were sought from appropriate providers including treatment equipment suppliers, water companies, self-lay pipework providers and plumbing contractors.

Despite a small sample size, the range of costs received demonstrates that reuse is a credible approach to significantly reducing average household water consumption and increasing resilience – particularly where councils are challenged by water stress. This is a scenario that is likely to become more commonplace as we build more of the homes that are needed and as climate change advances.

The need for evidence that water reuse works to reduce water consumption

Historically, where local planning authorities have attempted to include planning policies that encourage reuse, the Planning Inspectorate has dismissed them on the grounds of a lack of evidence. The financial burden associated with developments meeting such a policy has also been mooted.

The EWSC project considered the costs of both greywater and stormwater reuse. It also sought to understand whether there were certain development scales at which the cost per-unit of installing reuse became cheaper for either on-plot systems or community-scale systems.

Greywater recycling or reuse captures water from sinks, showers, baths, washing machines and other ‘wash water’ sources (but not from toilets, which would still discharge to the foul sewer). Greywater is usually more heavily contaminated than stormwater and hence will require the greatest amount of treatment to bring it up to appropriate standards for use. Greywater recycling is not affected by seasonality and climatic variances, but instead by the volume of greywater produced.

Stormwater harvesting captures rainfall running off rooftops and other hard surfaces in developments, such as pavements, driveways and so-on. This water will usually contain a wider range of contaminants and so may require higher levels of treatment, depending on the development of regulation for such water sources. However, there is scope to capture greater volumes of water than rainwater harvesting only and the approach – by virtue of having the potential to store more water – can provide more resilience to seasonal and climatic variances.

Findings of the Water reuse in new housing report

Findings indicate that:

• community-scale stormwater reuse is the most cost-effective type of water reuse, even for smaller sized developments of 40-50 homes;
• by comparison greywater reuse is more expensive, but more data is needed to reduce uncertainties;
• there is a significant fall in costs with development size up to around 100 units;
• higher density development sites yield lower costs.

This work represents a first step to fully understanding the costs of community water reuse. There will be a need for further work to:

• refine cost ranges and provider greater certainty by engaging a wider pool of product suppliers and supply chain contractors;
• understand the ways in which the costs of community-scale reuse might be reduced, for example by optimising drainage design at site level to capture water for reuse;
• investigate the operation and maintenance costs of reuse, and to compare total costs with alternative options for achieving water resource resilience.

With government recently reemphasising its commitment to significantly speed up the rate at which new housing is delivered, the issue of water availability will come under greater scrutiny. Bold action will be needed to deliver new water resources infrastructure but also improve water efficiency.

Water reuse will almost certainly become a necessary tool in the resilience box. This research helps to improve the understanding of how accessible on-plot and community-scale reuse is as a measure for planners, developers and the wider water sector.

Read the water reuse in new housing report here.

Author: Alastair Chisholm is director of policy at CIWEM.