One of Britain’s most polluting water companies has increased its payouts to shareholders by nearly 10% in the same week that it emerged it had pumped raw sewage into Windermere in the Lake District for 10 hours. United Utilities will pay its investors – which include some of the world’s biggest asset managers – £339m in dividends for this year, up from £310m for 2023, after it reported higher operating profits thanks to a rise in customer bills. The water company, which serves 7 million customers across north-west England, said its annual revenues had risen by about 8% to almost £2bn last year, mainly driven by a higher revenue cap, which was reset by the regulator to take account of inflation. United Utilities’ dividend windfall will flow to funds managed by major institutional investors, which include US finance giants Lazard Asset Management, Vanguard Group and BlackRock, as well as Legal & General Investment Management. The water company reported the shareholder windfall after it was revealed on Wednesday that millions of litres of raw sewage had been illegally pumped into England’s biggest lake earlier this year. United Utilities reportedly failed to stop illegal pollution of Windermere, in the Lake District, for 10 hours in February. The company did not report the incident to the Environment Agency until 13 hours after it started, according to a BBC investigation. The BBC cited United Utilities documents it had obtained that revealed that a telecoms fault on the night of 28 February had caused the main pumps at United’s Bowness-on-Windermere facility to stop. A set of emergency pumps then discharged untreated sewage into Windermere, which is part of a Unesco world heritage site. The company said the incident had been reported “within an hour of the pollution being confirmed” and as soon as the fault had been discovered its engineers “took urgent steps to resolve the situation”. In March, official figures indicated that last year nearly a third of United Utilities’ storm overflows had discharged raw sewage 60 times or more – the threshold for an Environment Agency investigation. Louise Beardmore, the company’s chief executive, said United Utilities had been ranked as the No 1 water and sewerage company for customer service in the independent UK Customer Service Index. “We take our role in protecting the environment very seriously; our ambitious business plan would see us investing more than ever before to improve services across the five counties of the north-west,” she said. “This would deliver a genuine step-change in infrastructure for the benefit of customers and the environment, and support 30,000 jobs.”