Billing problems accounted for 67% of disputes raised by customers in England and Wales.
Disputes over household water usage amounts and estimated bills has driven written complaints to firms up for a third successive year, an annual survey has found.
Billing problems accounted for 67% of disputes raised by customers in England and Wales with overall written complaints up 11% on last year to reach a five-year high, the Consumer Council for Water (CCW) said.
The total was skewed by Thames Water which was responsible for 42% of complaints the industry received despite only supplying 19% of domestic properties.
The company has now made a series of commitments to CCW to improve its performance, including reducing complaints by a quarter this year.
CCW said households had a right to expect clear and accurate water bills and be treated with empathy by suppliers if they slipped into debt, after finding concerns over bills dominated two thirds of the 93,758 written complaints made to companies in England and Wales during 2020-21.
Customers’ frustrations largely stemmed from disputes over how much water they had used, as well as the accuracy of estimated bills and the way some suppliers went about recovering debt.
CCW acknowledged Covid-19 had presented challenges for the industry but noted nine water companies were still able to reduce their written complaints.
Wessex Water and Hartlepool Water were the only two companies to receive top marks across the board for their complaint handling performance.
CCW chief executive Emma Clancy said: “We’re heading into a difficult winter for many struggling households as they deal with rising energy costs and other financial pressures so companies must not allow water bills to add to customers’ worries.
“Households have a right to expect clear and accurate bills but water companies also need to improve their communication and do more to understand their customers’ needs.
“That way they can ensure customers facing hardship gain quicker access to the support that exists but often goes untapped.”
CCW compared the performance of water companies on the number of written complaints they received per 10,000 connections, as well as assessing how well complaints were handled.
It said it was also keeping a “close watch” on Southern Water and Essex and Suffolk Water which it marked “poor” for both written complaints and complaint handling.
Both companies have also made commitments to CCW to improve.
Thames Water customer experience director Warren Buckley said: “We’re determined to do better, and while we’re heading in the right direction, we know there is a long way to go.
“We’ve been working closely with CCW to adopt and embed best practice across our organisation and have committed to reducing complaints across all our channels. We are investing in additional staff and implementing new policies to improve quality, including a new escalation team to proactively contact customers expressing dissatisfaction with our service.”
A Water UK spokeswoman said: “While it is encouraging that almost half of water companies have reduced the number of complaints they received year on year, all companies are working hard to bring complaints down, after their call centre capacity was dramatically limited over the last 18 months.
“We understand many customers remain concerned about their bills which is why there is an unprecedented level of support available for those in need.
“More than a million households are currently getting help to pay their bills, and that’s set to rise to 1.5 million. In addition, during the Covid-19 pandemic, water companies have provided more than 100,000 payment breaks to customers.”