Untied Utilities' plans to spend £1.5bn on upgrading its network have been approved by regulator Ofwat.
The projects form part of 33 infrastructure schemes worth £2.2bn involving water companies across the country. Work is expected to start in the next two years.
The total is around £600m more than Ofwat initially said it would allow the companies to spend after it emerged that United Utilities' projects would cost a lot more than it had previously agreed to.
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"The water sector needs to act now to secure future needs of customers and the environment," said the watchdog.
"The schemes we are confirming today will help tackle storm overflows, install more smart meters, provide additional water supply and improve river water quality.
"In each case the company has demonstrated a clear need and benefits to customers and the environment."
The lion's share of the money – around £1.7bn – will go to trying to tackle incidents where drains overflow when it rains.
The companies hope their efforts can reduce the number of spills by around 10,000 every year.
One of the investments will improve water quality at a swimming site on the River Wharfe at Ilkley, close to Bradford in West Yorkshire, and slash the number of spills into Lake Windermere.
Other projects include the installation of close to half a million smart meters, which can help companies manage usage better and detect leaks more quickly.
The approved schemes include a potential £1.5bn for United Utilities, £128m for South West Water, £99m for Northumbrian Water, £94m for Severn Trent, £81m for Yorkshire Water, £80m for Anglian Water, £70m for South Staffs Water, £64m for Portsmouth Water, £35m for Southern Water, £21m for Affinity Water and £3m for Bristol Water.
