One hundred and fifty properties in central Wellington are without water.
Wellington Water said it was notified about the problem affecting parts of Willis St and and Lambton Quay shortly before 7 am.
It said crews were checking valves in the area to find the cause of the outage.
The most recent update, issued just after midday, said the outage was expected to last for another two hours.
Even-numbered properties on Lambton Quay from Bowen St to Willis Street were affected, as were even-numbered properties on Willis Street from Lambton Quay to Boulcott Street.
Wellington has experienced a number of water problems in recent years, including sinkholes, burst pipes and leaks from ageing infrastructure.
The suburb with the most issues was on Tuesday revealed to be Wainuiomata.