A bedridden 98-year-old woman was billed £215 a month for water after “heavy usage” which was later found to be caused by a leak, and told if she failed to pay she risked having a bad credit record shared with other firms. Estelle Mendoza, who has dementia and is on NHS end-of-life care, was warned by Thames Water she had used the equivalent of more than a million cups of tea between September 2021 and March this year. Her direct debit was previously £33 a month. Thames Water failed to realise that the home in Ilford, Essex, where Mendoza has lived since 1948, had a possible water leak. It is claimed the company then gave her an impaired credit score over the mounting bills. Her son Lawrence, 68, said: “She has been treated dreadfully because they know she’s vulnerable. I noticed the increased direct debits being taken from her account, but they hadn’t flagged a possible leak.” Lawrence stopped the direct debits and complained about the treatment of his mother, who is not well enough to make a cup of tea. He said: “I was told she had been put on a credit blacklist after the direct debits were stopped. It’s appalling.” Ofwat, the regulator, announced last week that Thames Water was one of 11 providers in England and Wales being required to return about £150m to customers in the form of lower bills in 2023-24 after missing targets on pollution, supply interruptions, sewer flooding and other areas. Thames Water was one of the worst and will return £51m. Thames Water installed a smart meter for Mendoza in September 2021. It recorded the heavy usage, but failed to promptly flag a potential leak. In March, the company sent a bill warning she was using the equivalent of 5,698 cups of tea a day. It increased her direct debits more than sixfold. Lawrence says he has been in regular contact with the company’s complaints department and engineers since he spotted the increase in the direct debits in May. He has been told her credit information has now been updated to ensure it is no longer affected by the dispute over charges. A leak within the boundary of a property is the responsibility of the homeowner to rectify, but Thames Water offered to help find the source. A Thames Water spokesperson said: “We’re sorry for Mrs Mendoza’s experience and would like to apologise for any distress caused. “Our team are aware of her case and have escalated it to ensure an appointment is made for us to visit and investigate and, if possible, repair the leak on her property. “Once the leak is repaired, we will compare normal water use and provide a revised bill.” The company says it advises customers when it shares information with a credit scoring firm.