New guidance translates policy intent into buildable details, setting out a fittings-based route to verified consumption, options for rainwater and greywater systems and evidence from six live projects – aimed squarely at design teams and client bodies navigating planning delays in water-stressed regions

shutterstock water tap

With more than half of England now classified as seriously water-stressed, the document targets a growing delivery risk: no water, no homes

The Good Homes Alliance (GHA) has published Water Efficiency and Reuse in Housing: Design Guide for a Changing Climate, authored and edited by Pollard Thomas Edwards (PTE), to give architects, developers and housing associations practical tools for designing water-smart homes as scarcity tightens across England.

Framed around Waterwise’s hierarchy – reduce, reuse, offset – the guide moves beyond l/p/d (litres per person per day) targets to a fittings-based specification that aligns with the Building Regulations Part G and the direction of the UK Unified Water Label. The approach is designed to help schemes meet or exceed the government’s 110l/p/d ambition while producing verifiable, operator-friendly outcomes based on measured use rather than assumptions.

With more than half of England now classified as seriously water-stressed and planning in areas such as north Sussex and Greater Cambridge increasingly conditioned by water neutrality tests, the document targets a growing delivery risk: no water, no homes. The guide notes that smart-meter data from new developments often shows actual consumption around 145l/p/d – about 30% higher than design stage forecasts, underscoring the need to specify controls and components that perform in the real world.

Six case studies – from London luxury schemes to council housing and zero-carbon pilots – demonstrate routes that combine demand reduction (fittings and controls) with on-plot rainwater harvesting and, for denser typologies, community-scale greywater recycling.

Specification highlights for design teams

The model specification is intended for inclusion in project requirements and technical schedules. Headline measures include:

  • WCs: close-coupled pans with single 4l flush (or dual 3/4.5l where adopted). Preference for siphon mechanisms over flush valves to cut leakage risk, with 110mm pan outlets and accessible cisterns.
  • Showers: ≤7l/min thermostatic mixers, with no power showers. The guide encourages considering shower wastewater heat recovery (~40% heat reclaimed) to lower energy demand.
  • Baths: typical 139l capacity (max 170l), with overflow position controlling volume.
  • Taps: ≤5l/min on basins; ≤6l/min on kitchen sinks; simple lever operation for usability.
  • Appliances: dishwashers ≤1.0l/place setting; washing machines ≤6l/kg, both with high energy ratings.
  • Rainwater harvesting (RWH) – external use: minimum 250l storage per dwelling, with an option for smart water butts to automate irrigation and help manage runoff.
  • RWH – internal use (in water-stressed zones): tanks ≥4,000l per dwelling serving WCs and washing machines; two external taps (one rainwater, one mains). Systems to be designed early with UKWRA-member suppliers and installed to BS EN 16941-1:2024.
  • Greywater recycling (GWR): not advised for one-off houses due to cost/benefit, but effective at density (apartment blocks, purpose-built student accommodation, hotels) when centralised, designed/installed to BS EN 16941-2:2021 and backed by a maintenance contract.
  • Pipework and segregation: 15/22mm copper; dual, colour-coded non-potable pipework with signage at draw-off points and stopcocks; cross-connections only via AA/AB air gaps per the Water Supply (Water Fittings) Regulations 1999.
  • Meters, leaks and softening: smart metering on every home with resident dashboards and rapid alerting; whole-home leak detection; water softeners recommended in hard-water areas.

To tackle the design/operational performance gap, the guide emphasises measurable outcomes: smart metering, transparent reporting and fittings schedules that procurement teams can enforce.

GHA-Water-Guide-Images-model-specs

The guide moves beyond l/p/d targets to a fittings-based specification that aligns with Approved Document Part G

Policy context and what’s next

While the National Planning Policy Framework (NPPF) 2024 and the National Model Design Guide encourage on-site conservation and reuse, enforcement remains patchy. The guide anticipates tighter regulations – including DEFRA consultations on mandatory water labelling and updates to Building Regulations Part G expected in late 2025 – and positions the fittings-based method as future-proof and compatible with forthcoming labels.

A clear message to clients is to design in water systems from day one – allocating plant space in layouts, pre-installing dual pipework in stressed areas and assessing site-wide options on large schemes (such as communal rainwater harvesting, stormwater recycling, or local storage) alongside water sensitive urban design principles. The guidance also addresses human factors – from control ergonomics (easy-grip shower mixers) to resident feedback on dual-flush strength – aiming to prevent specification that looks good on paper but under-delivers in use.

Nicci Russel, chief executive officer at Waterwise, said: “Water scarcity is one of the UK’s most urgent challenges. To get our water use down to the lower levels we need all homes and businesses to be water-efficient – not just the kit in them, but also the people using it. This guide is a vital step forwards in that goal.”

The publication is the second in GHA’s Designing for a Changing Climate series (following the 2023 shading guide) and aims to influence design practice, planning policy and supply chains in tandem.