United Utilities is to submit its biggestever investment programme to Ofwat, the industry regulator.
The Warrington-based company says it needs to spend up to £3.8bn to meet higher drinking water and environmental standards demanded by both the British Government and Europe - with domestic and business users footing the bill.
For householders, it would see the year's average bill climbing from the current average of £245 to an estimated £550 - or £1.51 a day - by 2010.
People currently paying bigger water bills will be hit even harder, making Merseyside's water among the most expensive in the UK. Ofwat last night said it wanted water bills to rise by no more than single digits nationally.
But the regulator will not make a final decision on United Utilities' plans until November of next year when a figure for what it can charge customers will be announced.
United Utilities' managing director for customer sales, Bob Armstrong, said last night: "There will now be a long consultation process before Ofwat makes its decision in November, 2004. We will enter a period when people can influence the outcome."
Mr Armstrong admitted that the impact will be on customers, who will ultimately have to fund what is required.
"It will be a lot for people to pay and clearly significant in terms of possible increases.
"Arguably we pay the lowest in Europe for water and treatment services, and some people say we underpay and undervalue the resource."
Currently, the North West has the fifth highest water bills but Mr Armstrong admitted that the region could climb higher up the table under the proposed moves.