SEW boss Hinton apologised and admitted the crisis was a “failure”.
He said the outage was caused by a coagulant not performing as it should at the treatment works, which could have potentially compromised disinfection.
But this was disputed by the chief inspector at the Drinking Water Inspectorate, Marcus Rink, who said SEW was “flying blind” before December’s crisis.
The problem began almost three weeks before the company declared the emergency, he said.
In a letter to SEW, the chair of the select committee, Alistair Carmichael, said there were “serious questions about the accuracy and intent of the information” provided by Hinton.
SEW said it was currently reviewing the letter.
In 2023, SEW was found to be the worst company for supply interruptions in the UK.