Cambridgeshire's £20M Water Reuse System Sits Idle Through Drought While Regulators Work to Close a Gap
The UK's largest water reuse system, built into the Eddington urban quarter in Cambridgeshire, has not been switched on since it was made ready in 2021 because the Drinking Water Inspectorate (DWI) deems it non-compliant with drinking water regulations. The impasse has left a fully built infrastructure asset idle during the 2026 summer drought, which forced Cambridge Water and neighbouring Anglian Water to impose hosepipe bans as reservoirs ran low.
Cambridge Water designed and installed the system at Eddington, a mixed-use development by Cambridge University on the north-western edge of Cambridge that will eventually house 8,000 people. The development includes housing, student accommodation, academic research space, a primary school, and a nursery. The system works by using swales — shallow, vegetated channels — to capture rainwater and channel it into a lagoon that also protects nearby brooks from flooding. Cambridge Water then designed a treatment process to recycle that lagoon water back into homes for toilet flushing. Thousands of residents could save approximately 25 litres of water per person per day if the system were operational, according to The Guardian.
The regulatory friction sits at the intersection of two overlapping frameworks. Under the Private Water Supplies Regulations, all supplies derived from rainwater and recycled greywater — household wastewater from sinks, showers, and baths, as opposed to toilet waste — fall within scope of the regulations, as the DWI confirmed in a 2022 technical note. The DWI has also issued an Information Letter to water companies explaining how the existing regulatory framework applies to water recycling schemes. Separately, the Environment Agency's October 2025 position statement on water recycling for public water supply does not cover greywater reuse systems where non-toilet household wastewater is treated and reused to drinking water standards. Ofwat, the economic regulator for the water sector in England and Wales, maintains that any water supplied to customers must meet the same strict guidelines and testing as all other water.
The DWI has since assembled a group of experts to make recommendations for the governance of water reuse, with a focus on rainwater harvesting. The timeline for those recommendations is not specified.
Greater Cambridgeshire is one of the most water-scarce areas in the country, which makes the Eddington stalemate particularly acute. Lutz Johnen, chair of the UK Water Reuse Association, points to continental precedents: Belgium and Germany have operated household water reuse systems for more than 20 years. In Belgium, mains water use runs at roughly 90 litres per person per day, compared with about 140 litres per person per day in England and Wales. That 50-litre gap is not solely attributable to reuse, but the correlation is difficult to ignore for policymakers confronting supply constraints.
A parallel scheme at Clay Farm in Cambridge, documented in a June 2026 case study by the East Water Smart Consortium, is operational and achieving estimated savings of 20 to 25 litres per person per day, with residents aware of the system's presence and function. The contrast between a working Clay Farm installation and a dormant Eddington one illustrates that the barrier is regulatory rather than technical.
The broader context here is a regulatory architecture that was designed for conventional single-source public water supply and has not yet caught up with distributed, multi-source water reuse models. Think of it as a road network built for cars that now needs to accommodate bicycles: the physical infrastructure can be constructed, but the rules of the road have not been written. The Private Water Supplies Regulations scope language captures rainwater and greywater, but the governance pathways for how a water company operates such a system within a regulated public supply footprint remain unsettled. The Environment Agency's position statement explicitly excludes a category of greywater reuse, and the DWI's expert group on rainwater harvesting governance suggests regulators recognise the gap. Until that gap closes, utilities face a choice: build reuse infrastructure they cannot switch on, or rely on demand-side measures and restrictions during drought.
For the 2026 drought, that choice has already been made by default. Eddington's residents flush toilets with mains water while a lagoon of treatable rainwater sits metres away.
