South East Water loses 105 million litres a day and is, by the numbers, an average English water company. This part shows why even German-standard pipes would not close Kent’s gap, sets out what the company says it will build, and finds two things missing from its plan: the AI data centres now proposed for the county, and the sea off Thanet.
Disclosure: the editor of Kent Local News is the founder of GB Freedom, a registered political party which holds positions on immigration, housing and water recycling. This article relies only on published regulatory, statistical and company figures and on statements made on the public record.
The first thing anyone says about South East Water is the leaks. At the Horsebridge in Whitstable last week it was the figure that drew the loudest response: about 100 million litres a day, roughly a sixth of everything the company pumps. The instinct that follows is simple. Fix the pipes and the problem goes away. This part of the investigation is about why that instinct, though right about the pipes, is wrong about the problem.
How bad the leaks really are
Ofwat’s regulatory figure for 2024-25 is 104.8 million litres a day, against a target of 81 million, and up 8 per cent on 2019-20. Every piped network loses water; the question is how much. As a share of the water put into supply, the company lost 18.6 per cent in 2023-24 against an English average of 19.4 per cent. It is, in other words, an average English water company, and England is a mid-table G7 country.
| Country | Water lost from distribution | Source |
|---|---|---|
| Japan | About 10 per cent nationally; Tokyo 3.9 per cent | MLIT; Tokyo Metropolitan Government, FY2023 |
| Germany | About 6 per cent | OECD / EurEau |
| United States | About 16 per cent | American Water Works Association |
| England | 19.4 per cent (South East Water 18.6) | Environment Agency, water resources 2023-24 |
| France | About 20 per cent | EurEau |
| Italy | 42.4 per cent | ISTAT, 2022 |
Definitions vary between countries; some report all non-revenue water, others physical losses only. Treat the figures as indicative. Canada publishes no comparable national figure.
Why fixing them is not enough
Suppose South East Water leaked like a German utility. At 6 per cent of supply it would lose about 35 million litres a day instead of 105 million, freeing roughly 70 million litres. That is close to the whole of the new household demand the company expects from 550,000 more people by 2050, which Part A put at around 80 million litres a day. It sounds like the answer. It is not, for three reasons.
First, the company’s plan already assumes it. The 206 million litre shortfall it forecasts by 2075 is calculated after leakage has been cut by 23 per cent by 2030 and halved by 2050. The leak reduction is already spent in the arithmetic. Every litre the company saves from its pipes is a litre the plan is counting on, not a litre in hand.
Second, no network reaches zero. Germany’s 6 per cent is the best any large country manages, and Tokyo’s 3.9 per cent took decades and a pipe-replacement programme of a kind Mr Halsall told Whitstable “would cost billions”. The industry works to an “economic level of leakage”, the point beyond which finding and fixing the next leak costs more than the water it saves. South East Water has 14,500 kilometres of main. A third of its losses are on customers’ own pipes, which it does not own.
Third, leaks are a flow problem and outages are a peak problem. The May outage in Whitstable was not caused by water lost over months. It was caused by demand of 670 million litres in one day against storage that could not refill fast enough. Fixing leaks raises the average supply available. It does little for a network whose planning headroom is 7.2 per cent of demand when a hot weekend adds 15 per cent. That needs storage, treatment capacity and interconnection, which is where the plan turns next.
Leaks are a real failure, and the fines for them are deserved. But a reader who leaves the Horsebridge believing the county’s water problem is 100 million litres of leaks has been given the wrong number. The problem is that supply is being cut, demand is being added, and the pipes were only ever one line in a much longer sum.
What the company says it will build
The company’s published answer is more concrete than the meeting suggested, and it deserves to be set out fairly. On demand: cut leakage by 23 per cent by 2030 and halve it by 2050 against 2017-18 levels, and bring average use down towards the government’s 110 litres a day through smart metering, which Ofwat has funded at £25 million. On supply: a new reservoir at Broad Oak near Canterbury by 2035, yielding 22 million litres a day; a second Arlington reservoir in East Sussex; a water recycling plant at Peacehaven in 2041 giving 30 million litres a day; and a desalination plant at Reculver on the north Kent coast in 2046, giving another 30 million. In between, 23 local schemes are needed by 2030 to stop individual zones running short, plus 48 million litres a day of new transfer capacity between zones by 2075.
Ofwat’s settlement adds £266 million for resilience, including £90 million on interconnectors “that will reduce unplanned outages”, and £228 million to upgrade treatment, storage and network assets. The July redress package adds £5 million for on-site storage to manage peak demand, £5 million of free water butts and £5 million to bring forward business smart meters. All of it is now overseen by an Independent Monitor, paid for by the company, with a Remediation Plan that requires it to identify the root causes of its failures with an independent technical assessment. If it is delivered, and the monitor is there because Ofwat did not trust the company to deliver unwatched, Kent’s supply in 2035 will be materially more resilient than today’s.
The population the company is planning for is 2.26 million in 2019-20 rising to 2.81 million by 2050, from ONS projections and council housing plans that predate the revised targets. Its next plan, due in 2029, will have to add the homes councils have allocated since. It will also have to add something its current plan does not mention at all.
The blind spot: data centres
This publication searched the 156-page technical overview of South East Water’s plan. The phrase “data centre” does not appear. The company is not unusual: the Environment Agency’s National Framework for Water Resources, published in 2025, excludes data centres from its forecasts and calls their future demand “highly uncertain”, while the government aims to triple UK data centre capacity by 2030 and has designated them critical national infrastructure. A report for government in 2025 put the water use of a typical 100 megawatt data centre with evaporative cooling at about two million litres a day, and a 100 megawatt hyperscale site at 2.5 billion litres a year, “equivalent to the needs of 80,000 people”. It found that the plans “finalised in 2025 by water companies do not adequately account for” the sector.
The industry’s answer is closed-loop cooling, and it is a real improvement. Microsoft’s design, announced in 2024, fills the loop once during construction and recirculates it past the chips, saving it says more than 125 million litres per site a year. But closed-loop is not no-water. The heat still has to go somewhere, so the loop feeds chillers, which use more electricity, and electricity generation uses water. Many “closed” systems are hybrids that switch to evaporative mode when the ambient temperature climbs, which is to say in a heatwave, which is to say on the day Whitstable’s storage tanks are already at what the company calls a critical level. The Environment Agency’s own framework notes that data centre water use “rises in summer”. A site that draws nothing in February and two million litres on 24 June is not a small customer. It is a peak-day customer on a network with 40 million litres of headroom.
Two proposals now sit in or near the company’s area. Era4, formerly Carbon3.ai, has applied to build an AI data centre at Shelford Farm in Broad Oak, on the edge of Canterbury, beside the Shelford landfill and in the same village where South East Water plans its new reservoir, powered by landfill gas and solar. It says it will use closed-loop cooling and “a minimal amount of water each year, comparable to a large family home”, a figure this publication has asked it to substantiate. Canterbury City Council told Kent Local News on 9 September that the application (reference CA/25/02094/FUL), called in to the planning committee by two councillors and deferred on 21 July for a site visit despite an officer recommendation to approve, remains undecided; the site visit is due within weeks and the council intends to return it to committee in October. The officer’s report records that South East Water raised no objection, subject to conditions capping the site’s water use at 20 cubic metres a day and requiring approval of the cooling system, and states that the company “has confirmed that it has no concerns about supplying the facility with this volume of water”. Era4 has not responded to this publication’s questions. One of the councillors who called it in said that “at a time when we already have two existential crises with wastewater being dumped into our rivers and seas and water provision struggling to meet the scale of demand, and we know that AI data centres use massive amounts of water, there are serious worries”. Clearstone, on its promoters’ own public statements, proposes a 300 megawatt site on 145 acres of fruit fields between Northfleet and Southfleet, to go to the government as a nationally significant project in 2028, with construction from 2030. Its promoters have said AI could help find leaks. They have not yet said where the water would come from, and Dartford’s council leader has told them “we don’t like it and we don’t want it”.
The point is not that either scheme should be refused. It is that neither is in any water plan. If a data centre is connected to a network before the storage and treatment to serve it are built, the arithmetic is the one Whitstable already knows: the same tanks, the same 7 per cent headroom, one more large customer whose demand peaks on the hottest day. The taps run dry more often, and the company that is fined for it will be the one that was never asked whether it could cope. This publication has asked South East Water whether any data centre operator has approached it for a supply, whether its 2029 plan will include the sector, and has asked Era4 to substantiate its “family home” figure. Their responses are recorded below.
The other company: what went into the sea
South East Water supplies drinking water only. Whitstable’s wastewater goes to Southern Water’s Swalecliffe works between Whitstable and Herne Bay, where a £73.5 million upgrade begun in 2024 is not due to finish until 2030-31. The two companies are separate, but the pressures are the same, more people on ageing pipes, and on the sewage side the consequences are not abstract.
On 17 June 2021 a lightning strike knocked out Southern Water’s Foreness pumping station in Margate and raw sewage went out through the emergency outfall. Thanet council advised people to stay out of the sea at eleven beaches: West Bay, St Mildred’s Bay, Westbrook, Margate Main Sands, Walpole Bay, Palm Bay, Foreness, Botany Bay, Kingsgate Bay and Joss Bay among them, as the June heat brought the first crowds of the season. In October 2021 a power failure did it again, and the advice covered 14 beaches for eight days. In July this year Canterbury Crown Court fined the company £7.1 million for those and other discharges at Margate and Broadstairs between 2019 and 2021, one of them 16 million litres over two days. The Environment Agency’s Lindsay Faulkner told the court: “Southern Water allowed this repeated pollution to happen.” It was the company’s second appearance in that courtroom: in July 2021 it was fined £90 million for 6,971 illegal discharges off Kent, Sussex and Hampshire between 2010 and 2015, some 61,704 hours of untreated sewage.
Whitstable’s own experience is in its oysters. In May and June 2021 it was reported at the time that at least 100 people in the UK and 12 in Hong Kong had fallen ill with norovirus after eating Whitstable Oyster Company oysters, and the company halted sales; no causal link to particular discharges was established. SOS Whitstable, the group that filled the Horsebridge on 2 September, was formed that year by sea swimmers over the releases from Swalecliffe. In 2023 sewage was released into the sea near the town for 1,070 hours, up 65 per cent on the year before. The oyster company now has its stock tested for norovirus at the University of Kent before sale, a precaution a fishery should not need in a bathing-water town. Part 1 of this investigation found that 97 per cent of monitored water bodies in the Medway basin, and all of those in the Stour, fail the legal definition of good ecological status, and that eleven named Kent treatment works are at risk of breaching the dry-weather flow their permits allow. Spills fell 47 per cent in 2025, which was a dry year.
Sewage into the tap
Readers have asked whether treated sewage is already being recycled into Kent’s drinking water. It is not, yet, but it is coming. Southern Water’s Aylesford Water Recycling Project would take treated effluent from Aylesford wastewater works, purify it further, release it into the River Medway and abstract it downstream at Burham for treatment to drinking standard. When this investigation reported it in Part 5 in June, Southern Water’s plan had it operating from 2031. Its project page now gives consultation in winter 2027-28, a planning application in 2028, construction from 2031 and operation in 2035. South East Water’s own plan includes a similar scheme at Peacehaven in Sussex for 2041. The only such scheme running in England today is at Langford in Essex, since 2003.
A claim circulating locally, that businesses are served from the purest chalk water while households get the recycled supply, has no basis. South East Water draws 73 per cent of its supply from groundwater, and all of it goes into the same mains, to homes and businesses alike. Only firms with their own abstraction licences draw directly from the aquifer, outside the public supply, and that water never reaches a tap.
What Whitstable was owed
South East Water failed. Ofwat said so, the company’s chief executive said so, and the £30.5 million is the receipt. But the people who filled the Horsebridge were owed a fuller account than one company’s apology. They were owed the fact that the demand on their network is set by Whitehall and grows with every arrival; that fixing the leaks is already counted and would not be enough; that the plan to build reservoirs, recycling and desalination is real but reaches Whitstable in 2035 at the earliest; that nobody has yet planned for the data centres now proposed for the county; and that the sea they swim in is the other half of the same failure. Three articles is what it took to set that out. It should not have fallen to a local news site to do it.
Kent's water, Part B: why fixing the leaks will not be enough, and what nobody has planned for Quiz
8 questions
Sources
- Ofwat, Water company performance report 2024-25; Overview of South East Water’s PR24 final determination, December 2024; redress package and Independent Monitor notice, 14 July 2026.
- Environment Agency, Water resources 2023-24: analysis of the water industry’s annual performance; National Framework for Water Resources 2025; storm overflow event duration monitoring data 2025 (March 2026).
- ISTAT, Water statistics, March 2024; Tokyo Metropolitan Government, Water Supply in Tokyo, Business Outline 2024; MLIT Japan; American Water Works Association; EurEau / OECD national leakage figures.
- South East Water, Draft WRMP24 Technical Overview (pp.5, 7, 10, 24, 42, 110, 124–137); Local Democracy Reporting Service report of the Whitstable meeting, 2 September 2026.
- Water use in AI and data centres, report published on gov.uk, 2025; Microsoft, closed-loop data centre design announcement, August 2024.
- Canterbury City Council planning application CA/25/02094/FUL, Era4, Shelford Farm, Broad Oak, and the officer’s report to the planning committee of 21 July 2026; Canterbury City Council response to Kent Local News, 9 September 2026; Clearstone, Northfleet/Southfleet NSIP proposal, consultation autumn 2026.
- Environment Agency press notice, Southern Water sentencing, Canterbury Crown Court, 17 July 2026; sentencing 9 July 2021 (£90m).
- Thanet District Council advice notices, June and October 2021; Whitstable Oyster Company closure reports, June 2021; CADDA / University of Kent norovirus monitoring, 2025.
- Southern Water, Swalecliffe improvement scheme and Aylesford Water Recycling Project (project pages); Essex & Suffolk Water, Langford recycling scheme.
- Kent Local News, Water Investigation Parts 1, 2 and 5 (May–June 2026).