The complex computer systems which control London’s drinking water supplies have been upgraded while keeping the taps running in a “monumental” £20 million project by Thames Water.

Moving from the 25-year-old RTAP system to the new ClearSCADA platform saw the replacement of multiple legacy and obsolete systems, while keeping customers in supply across the capital.

One of the largest of its type in Europe, the technology monitors output from the five big treatment works in London – Hampton, Coppermills, Walton, Ashford and Kempton – as well as more than 200 service reservoirs, pumping stations and boreholes, many of which are unmanned and need to be operated remotely.

Carly Bradburn, Thames Water’s head of digital operations, said: “The computer system oversees the production, treatment and delivery of up to 2.2 billion litres of drinking water every day. Replacing it has been a very complex and challenging project.”

The previous system had been more than 25 years old and software updates no longer available. Replacing it needed the engagement of multiple stakeholder groups, external suppliers and companies, something that been a vast undertaking.

The commissioning of the new system required checking and validating more than 700,000 data points, and around 100,000 functional, mimic, alarm and user tests to ensure minimal operational disruption and risk.

“This has been a monumental achievement,” she said. “What once seemed impossible has been done.”

It took several months to migrate over to the new system, supplied by Schneider Electric, which ran alongside the old system to resolve any problems, before taking full control of the whole estate.

Mark Grimshaw, Thames Water’s head of London water production, said: “Investing in resilient systems and assets is one of our key priorities. There can’t be many more important projects than updating the technology that ensures a reliable water supply for one of the world’s major cities.

“Keeping the old system up and running while launching the new system alongside it has been a monumental effort by everyone involved – a great example of teamwork at its very best.”

Thames Water is the UK’s biggest water and wastewater services provider. Its key workers provide essential services around the clock to 15 million customers across London, the Thames Valley and surrounding areas.

For an average of just over £1 a day for each household, it provides 2.6 billion litres of drinking water and safely remove 4.6 billion litres of wastewater every day.

It invested more than £1 billion again in 2019/20, leading to a total of £16 billion in the past 16 years.

Mark said: “We will continue to spend wisely on improving resilience, service and efficiency, as well as provide more support for customers in vulnerable circumstances.

“We also have additional responsibilities to society and the natural environment. What we do and how we do it delivers significant public value, which is why we have ambitious plans to self-generate more of our own power, reduce our carbon emissions and increase biodiversity across our sites.”