The water quality crisis for some 20,000 people living in Tunbridge Wells has been continuing on and off since early December. The cause is a malfunction at the Pembury Water Treatment plant (WTP), meaning that water from the taps in many Tunbridge Wells homes is not safe to drink. South East Water, which is responsible for this WTP, is supplying bottled water from various collection points.
In fact, the Drinking Water Inspectorate (DWI), one of the regulatory agencies for water, has been warning about the risks at Pembury WTP since at least 2024. A new microfiltration system was needed, but this was not installed. The water has become unsafe to drink, which triggered the ban for thousands of households.
Poison water
Water treatment requires settling tanks, adequate filtration and chemical inputs. An accident with the chemicals can be lethal. The accident at Camelford in northern Cornwall in 1988 (investigated in an excellent film now available via BBC iPlayer, Poison Water) was caused by a relief driver delivering a load of aluminium sulphate, a coagulant, straight into the output tank of the WTP, at a time when it was unstaffed.
This produced water with excessive acidity (sulphuric acid), which killed fish instantly, followed by young piglets in the same week, and then affected many human victims whose lives were blighted by organ damage. They were never compensated in spite of seeking legal redress. Nor did the CEO and management of the local company properly acknowledge their guilt and responsibility.
Problems at Pembury
By comparison, local Tunbridge Wells residents discussing the causes of the current drinking water ban quote the following summary (from AI):
- Drinking Water Inspectorate (DWI): Found significant risks at Pembury, with reports of poor filter performance, inadequate coagulation management, and reliance on manual intervention.
- Failure to Act: The DWI noted SEW failed to install a crucial microfiltration system despite prior warnings, and proper testing wasn’t done, meaning the failure “shouldn’t have been a surprise”.
- Managerial Issues: A stand-in scientist managed the site when the primary process scientist was unavailable, contributing to the problems.
In essence, a chemical error compounded existing infrastructure and management issues at the plant, leading to a major, predictable crisis.
Hush-up at Camelford
Sources of information are mentioned by South East Water (SEW), the recent enquiry in Parliament, and discussion among affected residents on Facebook. Just as at Camelford all those years ago, the residents want to know exactly what is in their cloudy water.
The TV programme on the Camelford accident shows how a local scientist joined with others determined to get a chemical analysis. The science involved concerns not only what can poison water but also how poison affects human (and animal – those dead fish and piglets!) bodies. A major opportunity was missed to use data from Camelford for further scientific research on this. But the government enquiry at the time was a hush-up operation because the government did not want to scare off potential investors on the threshold of launching water privatisation, the TV programme insinuates.
The evils of privatisation?
Some media commentators, like Feargal Sharkey, have leapt in to utilise the current SEW incident as another proof of the evils of privatised water. The CEO, David Hinton, has actually refused some media interviews, saying that they would turn into an argument about his salary rather than discussion about the incident itself. One salient point he has made is that SEW needs to improve the infrastructure so that water for the affected area can also be switched to come from the Bewl reservoir. It is not clear how much this would cost or the expected dates when this would be achieved.
Resilience
Planning for resilience is a vital aspect of engineering, and indeed for any of the apparatus of our lives that depends on complicated science-driven processes. But the cost of this is often ignored. It includes both human and material resilience.
At Pembury WTP, a temporary scientist was in charge when the wrong coagulant was put in because the main scientist for that operation was ill. Does this mean there should always be two scientists at that WTP or that SEW needs to spend more money on paying for temporary water scientists? Or that England as whole needs to set aside more money for a pool of such scientists? This resembles the arguments about temporary teachers, or care assistants, or even doctors. Is it cheaper to enlarge the permanent team or to rely on the temps? And can the temps provide good enough professional service?
Solutions for material resilience in this Tunbridge Wells case have been suggested, such as first, renewing outdated pipes (Pembury water works was first opened in the nineteenth century, but much of its plant (tanks and pipes) is from the 1930s), and second, connecting the local system to an alternative source at Bewl for emergencies.
Growing population, lack of water
But there are some larger problems. Climate change, implicated in the exceptionally dry spring and summer of 2025, has caused reductions in the chalk aquifers that supply this region. That is why the tanks did not refill fast enough. Furthermore, increased population and housing means there are more customers for these sources to supply. In the south east, our average household use of water exceeds what it should be once planning for climate change is calculated. This requires a massive culture change in how we use water: drastic re-engineering in our houses combined with a huge public education campaign.
Alternatively, we could go for the engineering solution suggested way back in the nineteenth century: to pump water to the thirsty south east from Wales, which would be a major and costly undertaking. Let’s hope that the building of the new reservoir at Canterbury will render that unnecessary.
New Ofwat initiative
‘Public water supplies are projected to fall short by 5 billion litres per day by 2055, risking higher bills and environmental damage.
To help respond to this urgent challenge, Ofwat has established the Water Efficiency Lab – a new £25 million challenge-led competition to unlock and scale innovations that reduce water use across England and Wales.’
The challenge is to help customers understand their water use, as 94% of customers underestimate their consumption. The water innovation prize is for something that changes customers’ behaviour in water use.
Remedies, compensation and finance
The MP Mike Martin is calling for Hinton’s resignation. Residents are asking about compensation. The enquiry will report in April. But just finding out who or what to blame will be insufficient without deciding on remedies.
If what water companies need is more finance, then this should be considered. Unlike Sharkey et al., I am against re-nationalising water companies, as I do not think the government will be any more ready than the big capital investors to spend money on resilience. What I favour is compelling the water companies to become public benefit companies and giving tax incentives, underwritten by bond-like guarantees from HM Government, to British ISA investors to invest in them. Local consumers would then be the local investors, with more say over how much should be spent on resilience of the drinking water supply.
It remains to be seen which approach will be adopted, but investment in resilience will be essential to make the UK’s water supply fit for the future.
Image by Jos Speetjens, free to use under the Unsplash licence.
