Thousands risk having their tap water turned off due to reservoir repair farce

A giant reservoir in Sussex with enough capacity to supply tens of thousands of homes has not been used this summer due to faulty treatment works, despite the surrounding area facing water shortages. Weir Wood reservoir has been out of action for seven years due to problems with the adjoining treatment works, which means the water cannot be made safe for human consumption. Repairs to the treatment works were initially supposed to be completed by 2024 but are now not expected until at least 2030 after the site’s owner, Southern Water, widened the scope of the work. Shorts The project continues to experience delays in part due to a dispute between Southern Water and the regulator Ofwat over how the new treatment works will be funded. Meanwhile, almost 100,000 homes in the surrounding area, which are served by South East Water, are facing shortages due to the ongoing drought across much of England. Treatment plant infected with bacteria The problems at Weir Wood treatment plant date back to 2018, when the Drinking Water Inspectorate issued a notice prohibiting its use after it became infected with bacteria following an outage. The rebuild of Weir Wood treatment works was initially expected to be complete by 2024 but this date has now been pushed back to 2030. Uncertainty remains over the project due to a disagreement between Ofwat and Southern Water over how this should be funded. As part of a five-yearly review process in which Ofwat decides how much bills can be increased to fund infrastructure upgrades, Southern Water requested £74.3m to fund the rebuild, but Ofwat refused this full amount. In its 2025 annual report, Southern Water said the outages at Weir Wood, alongside three other reservoir projects, made some areas more vulnerable to drought. However, the water company has been able to rely on supply from other sources to date to avoid shortages. In the past, Weir Wood reservoir has been used to supply homes in Sussex that are now facing shortages (Photo: Dan Kitwood/Getty) Almost 100,000 at risk of shortages Due to the failures at the treatment plant, Weir Wood is one of the few reservoirs in England that are currently near capacity, with latest data showing the site was 85 per cent full. Reservoir storage has fallen to an average of 58 per cent nationally, while nine are now classed as exceptionally low. This includes Ardingly reservoir, which is roughly six miles away from Weir Wood and supplies water to almost 100,000 households in an area of Sussex that includes the major towns of Burgess Hill, Haywards Heath and East Grinstead. South East Water recently warned these households are at risk of having their water turned off on a rota basis this winter as Ardingly reservoir dropped close to 30 per cent capacity. Typically these households would also receive water supply from Weir Wood as part of a supply agreement between Southern and South East Water, which means the area is more vulnerable to shortages while the plant is out of action. South East Water has applied to the Government for a drought permit that would see environmental rules relaxed in order to protect the region’s water supply. Dr Justin Neal, Head of Legal at WildFish, said: “If the country’s long-term water supply had been properly planned and managed, we likely wouldn’t be in this situation. “Time and time again, water companies turn to drought orders as a cheaper, short-term solution – and our rivers and streams pay the price for this failure to invest for the long term.” As a longer-term solution, South East Water has proposed building a 13km pipeline from Weir Wood reservoir to Ardingly to supply water to the region, but this is yet to be approved. This part of Sussex has already experienced a number of water outages in recent years, including in January when almost 20,000 homes in East Grinstead received little or no water for almost a week. South East Water blamed the shortages on Storm Goretti causing burst pipes and power outages. Mims Davies, Conservative MP for East Grinstead and Uckfield, said the area has suffered due to a myriad of issues, including “poor communication between the water companies and terrible weather without the infrastructure and the backup that they properly needed”. She said water supply problems impact businesses, pointing to the example of one hotel that lost around £250,000 due to January’s shortages. A spokesperson for Southern Water said: “We are progressing plans to comprehensively redevelop and modernise Weir Wood Water Supply Works through a major investment programme. “The project will involve the complete replacement and upgrade of key treatment processes and associated infrastructure, creating a modern facility that will help strengthen water supply resilience across North Sussex for decades to come.”