Water companies are forecasting an above-inflation rise in average household bills in April, drawing criticism from campaigners.
The average annual water and sewerage bill is expected to rise by 6% in England and Wales, up £27 to £473, says suppliers' trade body Water UK.
In Scotland, water and waste charges will go up by 8.8%, a rise of £36.
Water firms have been facing intense scrutiny after the dumping of sewage into rivers.
"Next year will see record levels of investment from water companies to secure the security of our water supply in the future and significantly reduce the amount of sewage in rivers and seas," said David Henderson, chief executive of Water UK.
He said companies in England and Wales would invest more than £14.4bn in the next financial year, the highest annual investment on record.
Bills can vary
The average expected bill is calculated by companies, and will be above the latest inflation rate of 4%, which charts general price rises. Actual individual bills can differ significantly owing to
regional variations and usage levels for those on a meter.
In England and Wales, Wessex Water and Anglian Water are at the top end of the scale, with average bills set to increase to £548 and £529 respectively, while Northumbrian customers will see the lowest average bills of £422.
A host of companies were told by regulator Ofwat last year that they would have to
limit rises owing to missing key targets on leakages, supply and reducing pollution.
The watchdog has also told suppliers that they must offer help to those who were struggling with bills.
"We are very aware, for those who are already struggling, this will be a real worry. As such, water companies must do all they can to protect those who are most in need of a helping hand," said chief executive David Black.
More than a million households in England and Wales get cheaper bills through companies' social tariff schemes, saving them an average of £151 last year. Around half of households in Scotland receive financial support with water charges.
Five water companies use some of their own profits to help fund social tariffs, with consumer groups are calling for others to join them.