Non-domestic unmeasured customers will pay 3.5% more, despite retail price inflation running currently at around 5.3%.
Liam Mulholland, Interim Head of Customer Services at NI Water, said: "Whilst these increases are unavoidable, we are very conscious that these are difficult economic times for our customers. We have, therefore, gained agreement to limit any tariff increases to less than inflation."
He also said that information leaflets have been mailed to Northern Ireland's 90,000 non-domestic customers explaining the rises and adverts outlining the changes have run in daily newspapers.
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NI Water is one year into its first price review, under which the regulator set a scheme of charges for 2010-13.
Last December, then Stormont Finance Minister Sammy Wilson said there are no plans for water charges for domestic users over the next four years.
The pledge was part of the budget that Mr Wilson presented to MLAs at Stormont for approval.
Meanwhile, as the May Assembly election looms, the Alliance Party has committed to bringing water charges to the province, while the UK Independence Party (UKIP) are fundamentally opposed to the introduction of water charges.
UKIP NI Chairman and South Down Assembly candidate Henry Reilly said: "In these tough economic times the last thing the people of Northern Ireland need is to be burdened by yet another expensive tax that they cannot afford.
"Rather than introducing water charges and yet more levels of bureaucracy we need to create an efficient water service which serves the needs of local people.
"The mismanagement of the water service in Northern Ireland over a period of years simply highlights why an effective voice of opposition is needed to hold Stormont to account," he said, this week.
(BMcC/GK)
