Open letter: Making Water-Smart Buildings the New Normal

On behalf of its members, partners and supporting organisations, Future Water has written an Open Letter (below) which needs your support.

England faces a growing public water supply deficit, and building 1.5 million new homes will push demand higher. Water-smart buildings, using water efficiency, rainwater harvesting and greywater reuse, can cut demand for drinking water with technology that already exists. We're calling on Government to make them standard practice.

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‍Open letter: Making Water-Smart Buildings the New Normal

We write as members and partners of the Future Water Association, together with organisations from across the built environment, facilities management, education, healthcare and innovation sectors. We share a common view that the UK must make better use of the water resources it already has if it is to meet its ambitions for housing, economic growth and climate resilience.

The Government is rightly focused on delivering economic growth, addressing cost of living pressures, increasing workforce participation and fulfilling its commitment to build 1.5 million homes during this Parliament. At the same time, England faces a projected public water supply shortfall of around five billion litres per day by 2055 if action is not taken. The Climate Change Committee has repeatedly highlighted water efficiency as a critical component of climate adaptation, particularly as the country faces hotter, drier summers and increasing pressure on water resources.

Recent analysis published in Bricks and Water: Building the Case for Water Efficiency and Reuse highlights that water efficiency and water reuse must become a central part of housing delivery if England is to meet both its housing and water resilience ambitions. The report concludes that reducing demand through more efficient homes and wider adoption of non-potable water systems can help alleviate pressure on stressed water resources while enabling sustainable growth in areas where water availability is already a constraint.  

Addressing this challenge requires a balanced approach. Leakage reduction and improved water efficiency must remain the primary tools for reducing the supply-demand deficit. Water companies, regulators and government are already investing significant effort in these areas. However, these measures alone are unlikely to be sufficient. Water reuse, through rainwater harvesting and safe greywater recycling, provides an additional practical and proven tool that can help close the gap while reducing pressure on drinking water supplies.

Water-smart buildings are based on a simple principle: use high-quality drinking water where drinking-quality water is required and use appropriately treated non-potable water where it is not. Rainwater and treated greywater can safely supply toilets, irrigation systems and other non-drinking applications, reducing demand for treated potable water without compromising public health.

Importantly, much of the infrastructure and expertise needed already exists within industry. Government's role is to provide the policy direction, regulatory clarity and market signals necessary to enable wider adoption and remove barriers to implementation.

The technologies are available today. The evidence base continues to strengthen, and the Drinking Water Inspectorate has already established a framework for managing risks associated with non-potable water systems. We therefore urge government to work with industry to make water-smart buildings a standard feature of new developments and to create practical pathways for retrofit across existing building stock.

What We Are Asking Government To Do

1. Support Water-Smart New Development

The Government's commitment to deliver 1.5 million new homes presents an opportunity to embed water resilience into future communities from the outset. In many water-stressed regions, housing delivery is already constrained by concerns over water availability. Water-smart development can help remove those constraints while improving long-term resilience.

As highlighted in Bricks and Water, new homes must be both housing-ready and water-ready. The report identifies water efficiency and water reuse as critical enablers of sustainable housing growth in water-stressed regions.  

We therefore propose that all new developments should be designed to accommodate non-potable water systems from the outset.

This should include:

• Rainwater harvesting systems where technically viable, designed in accordance with BS EN 16941-1:2024.

• Non-potable pipework infrastructure for toilet flushing and irrigation.

• Appropriate commissioning, backflow protection, identification and inspection regimes.

• Centralised rainwater or greywater systems within larger multi-occupancy buildings where scale supports viability.

• Monitoring and disclosure of performance to build the evidence base.

Evidence from the Affinity Water and WRc Project Zero programme suggests that dual-plumbed developments could reduce potable household water demand by approximately 23%, with separate non-potable supplies used for applications such as toilet flushing. The programme found that around a quarter of household water demand does not require drinking-water quality and can be supplied through properly managed non-potable systems.  

Research undertaken through the Project Zero programme also indicates that rainwater harvesting systems designed to current British Standards can continue to meet the majority of non-potable demand under future climate scenarios. While supplementary mains water may still be required during prolonged dry periods, these systems represent a practical and proven mechanism for reducing reliance on potable water supplies.  

Embedding water reuse readiness within Part G of the Building Regulations would support both housing delivery and long-term water resilience.

2. Create Practical Retrofit Pathways

Although new-build requirements are essential, existing buildings will continue to account for the vast majority of water demand for decades to come.

Government should therefore establish clear expectations for water-smart upgrades during major refurbishment programmes, including:

• Bathroom and kitchen replacement cycles.

• Major roof works.

• Estate modernisation programmes.

• Public sector procurement and estate upgrades.

A phased "water-smart ladder" approach would enable adoption according to opportunity and cost.

At the simplest level, households and businesses could install water butts and rainwater diversion systems. Planned maintenance cycles could incorporate higher-efficiency fixtures and appliances. Larger refurbishment projects could support communal rainwater harvesting and greywater reuse systems where these offer economic and operational benefits.

This approach aligns water reuse with normal asset management cycles rather than creating unnecessary disruption.

3. Align Water Efficiency Standards and Water Reuse

Water efficiency and water reuse should not be treated as competing solutions. The greatest benefits will be achieved when both work together.

We therefore support the introduction of mandatory water efficiency labelling and the continued development of minimum performance standards for water-using products.

Alongside this, government should review regulatory barriers that may limit innovation in emerging technologies, including advanced reuse systems and recirculating water technologies, while maintaining appropriate public health protections.

A coordinated approach would encourage manufacturers, developers and consumers to invest in solutions that reduce overall water demand and household bills.

The Evidence for Action

The case for water-smart buildings is increasingly compelling.

Evidence from water companies, industry research and independent policy analysis suggests that water reuse can reduce demand for treated drinking water, improve drought resilience and defer investment pressures on strategic supply infrastructure. Reuse systems can also contribute to lower whole-life carbon emissions when compared with expanding potable water supply networks.

The findings from Affinity Water and WRc's Project Zero programme demonstrate that around 23% of domestic potable water demand could be met through a non-potable supply network. This aligns with previous studies into household water demand and reinforces the potential contribution of dual-plumbed developments to reducing pressure on water resources.  

Internationally, countries including Germany, Denmark, Australia, Japan and Spain have demonstrated that rainwater harvesting and dual-supply systems can be implemented safely and successfully in domestic and commercial settings. This is consistent with guidance from the World Health Organisation, which sets out risk-based approaches for the safe use of recycled water and greywater systems.

There are wider economic benefits too. Expanding water reuse would create opportunities for new skills, specialist installation and maintenance services, manufacturing and product innovation. Over time, it could support a growing domestic supply chain whilst helping consumers gain greater control over water use.

At a time when millions of households face affordability challenges, every practical measure that can improve resilience and reduce long-term pressures on water resources deserves consideration.

Delivering Reuse Safely and Responsibly

Drinking water quality must remain paramount.

Water-smart buildings are not about reducing standards for potable water. Rather, they are about ensuring that the right quality of water is used for the right purpose.

The Drinking Water Inspectorate has already established guidance on governance, competency, risk management and operational controls for non-potable systems.

International standards and guidance from the World Health Organization further demonstrate how these systems can be operated safely. WHO guidance promotes a risk-based approach to water reuse, supported by monitoring, management controls and clearly defined end uses.  

Key requirements include:

• Clear separation between potable and non-potable systems.

• Appropriate backflow protection.

• Robust design standards.

• Effective operation and maintenance arrangements.

• Clear labelling and customer information.

• Competent installation and inspection processes.

By focusing on recognised standards and proven operating models, government can support wider adoption while maintaining public confidence.

Drinking water for drinking and cooking. Reused water for toilets, irrigation and other suitable non-potable uses.

A 90-Day Action Plan

We recognise that government, regulators and industry are already exploring ways to improve water resilience through initiatives led by Defra, the Environment Agency, Ofwat, RAPID and others. This letter seeks to support and accelerate that work rather than duplicate it.

We therefore propose the following actions within the next 90 days:

1. Publish a policy statement setting out the Government's intention to support water-smart buildings and providing an indicative implementation timetable.

2. Establish a cross-government taskforce involving Defra, MHCLG, DHSC and DfE to align policy, regulation and procurement.

3. Launch a national demonstrator programme covering housing, education, healthcare and commercial buildings.

4. Confirm the timetable for mandatory water efficiency labelling and associated minimum standards.

5. Commission the development of implementation guidance for water-smart developments and retrofit projects.

Our Offer of Support

The sector stands ready to help.

Future Water Association members and partners can provide technical expertise, operational evidence, industry insight and demonstrator projects. We can support government and regulators in developing guidance, building the evidence base, evaluating pilot projects and convening stakeholders from across the water, construction, manufacturing and property sectors.

Together we can create a practical, proportionate framework that supports housing growth, helps address water scarcity, reduces costs and strengthens the UK's resilience to climate change.

Signed,

Future Water Association members and supporting organisations.

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