Guernsey Water says increasing household bills by between £5 and £7 a month will help it offset higher maintenance and investment costs.
The States-owned utility says since 2018 its charges have increased by less than inflation.
But from 1 January 2024, metered customers will pay around 11% more, while unmetered customers see a 12% rise - this is double the current rate of inflation.
Guernsey Water says this is to cover the rising cost of its 'vast network', which it calls 'the island’s most critical infrastructure.'
This includes 14 reservoirs, extensive underground pipes, and a wastewater centre.
Anyone concerned about the charges is asked to contact the company.