Thames Water first admitted fears of “serious” risks to water supply at Coppermills in 2019 but renovation work will only finish in 2032, prompting concern that the ageing site could fail before then, reports Marco Marcelline
Concern is growing at the state of Thames Water’s ageing Coppermills Water Treatment Works in Walthamstow, amid reports that a “single fault” could cut off water supply for millions of Londoners.
The Walthamstow site is Thames Water’s main treatment works in London and provides water to approximately three million people.
Interruptions stemming from a failure at Coppermills could leave Londoners unable to use their showers, or flush their toilets.
In its business plan for 2025-2030, Thames Water states that such an interruption could mean customers going without water for a “significant period of time”.
Thames Water is understood to have first relayed concerns of the potential for “serious” risks to the water supply at Coppermills to watchdog Ofwat in 2019, when it presented an investment plan for improvements.
However, that £350million plan for works, which included algal pre-treatment and the duplication of the high-lift pumping station, was slapped down.
In its refusal, Ofwat said Thames Water’s supplied case for the works was “weak”, stating there had been “poor risk analysis, inconsistent prioritisation, and an absence of evidence showing that Coppermills-related investments were optimal or urgent relative to other risks”.
Ofwat also admonished Thames Water for wanting to wait until 2025-30 for works, describing the delay as “not appropriate” in the context of the potential water supply risks at Coppermills outlined by the company.
Instead of approving the requested funding, Ofwat granted a conditional £180m for Thames Water to immediately re-evaluate its Coppermill proposal and undertake a rigorous resilience assessment.
Ofwat eventually approved a £400m funding package last year, with the money going towards replacing the pumping station, a new electricity substation, slow sand filter recirculation system, as well as fresh pipes, chambers and control structures both above and below ground.
But the work, which will begin in spring 2026 and finish in summer 2032, has raised alarm for being a “patch and mend” operation that is happening too late.
In July, Sir Jon Cunliffe, a former deputy governor of the Bank of England, said in a speech announcing the findings of his independent review into the water sector that the Walthamstow facility “is on its last legs”, adding that the fact the site is only now being overhauled is indicative of “a patch and mend approach”.
Speaking to the Financial Times, Cunliffe said when he visited Coppermills earlier this year, water was leaking into the engine hall that houses electrical pumps.
He said: “I’m not suggesting it will fail, but why is this [work] just starting now when I can see the water coming through the roof and they’re telling me it’s been like that for years?”
Areas of specific concern are the centre’s 1960s high lift pumping station, failure of the slow sand filtration process, and drainage issues in the contact tank.
The Echo understands that there was a microbiological incident in March 2023 caused by untreated water entering the contact tank. The water contained cryptosporidium, a microscopic parasite that can cause a potentially dangerous illness called cryptosporidiosis. The parasite thrives in the intestines of infected humans and animals and is passed out in their faeces.
According to the UK Health Security Agency, cryptosporidiosis symptoms include severe watery diarrhoea, vomiting, stomach cramps, nausea, fever, and loss of appetite. It can last for around two weeks and anyone can catch it although it is particularly common in children between the ages of one and five.
In response to the contamination incident, the Drinking Water Inspectorate issued Coppermills with a notice enforcing it to continuously sample its water for cryptosporidium. The notice additionally mentions the centre must check for any “animal ingress” into any exposed open-air treatment stages, and carry out “appropriate analysis and disposal of any animal carcasses”.
Thames Water said in a statement: “Thames Water has the oldest and most complex assets in the country and that is why we have embarked on the largest ever investment programme, delivering the biggest upgrade to our network in 150 years. We have ambitious plans to deliver improvements over the next five years by investing more than £20bn to address asset health.”
“Our £400m work for Coppermills is part of our planned investment to secure the ongoing resilience of our assets in light of London’s growing population and climate change. Taken together, these investments will help secure an ongoing supply of safe, clean, wholesome drinking water to our customers.”
Thames Water added that it took water quality “extremely seriously” and that “since 2010 more than 99.95% of tests” taken from customers’ taps met the standard required by UK legislation.
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