Water companies will be forced to pay out a net total of £70m to customers after falling short of performance targets.
The fines for underperforming suppliers will be passed onto customers through lower bills over 2024 and 2025.
Most companies failed to meet key targets on reducing pollution, leakages and supply interruptions, industry regulator Ofwat has confirmed.
Ofwat judges the performance of water companies in England and Wales each year against the “stretching” targets they set in 2019 for a five-year period until 2025.
Thames Water will be ordered to pay out the most to its 15 million customer base, of nearly £74m.
The struggling firm faced crisis talks earlier this year over its massive £14bn debt pile, but it managed to secure an emergency funding package from shareholders.
The watchdog last month said Britain’s biggest water supplier has “significant issues to address” over its financial strength.
Anglian Water customers will see more than £27m taken off their bills and Dwr Cymru about £24m.
Meanwhile, some companies will be able to charge customers more after improving their performances, according to Ofwat.
Severn Trent Water will be allowed to add £89m to the bills of the 4.6 million customers it serves from next year and United Utilities can charge more than £25m.
Ofwat said 12 firms will have to return around £193m to customers, partially offset by five firms charging about £123m more, resulting in a net total of £70m being paid out.
The regulator had said in September that firms would return a net total of £114m, but that amount was provisional until the review process was completed.
