The lack of water -- caused by the malfunction of an in-building water pump and its backup at around 11am -- meant WebCentral was unable to keep its data centre's air conditioning systems operational.
"The air-conditioning has now reached a critical point and we have been forced to shut down all data centre facilities at Wickham Street in a controlled way to minimise damage to servers and other equipment," said a statement placed on the company's Web site.
"Water supply has been re-established, but it will take some time for the cooling towers to replenish and air-conditioning to return to normal."
The statement noted WebCentral had initially shut off all non-essential services in an attempt to reduce the impact of the water supply issue.
David Lammey, the company's general manager of consumer and business, said that WebCentral first became aware of the problem around 11:15am, and confirmed the extent of the outage.
"It was the entire data centre at Wickham St that went down, ranging from our shared up to our corporate customers," said Lammey.
Lammey couldn't confirm how many customers had been affected, but said it was probably under a thousand.
"I know that across the business, in business and consumer, I've got over 60,000 accounts," he said.
"The great majority of those are over in our other datacentres. Exposure wasn't minimalised but it certainly wasn't a majority scenario."
He added most customers' services had been restored around 3pm, and said WebCentral would be working with customers individually to determine how the outage would affect their contracts financially.
Because the building hosts several other data centres operated by other companies, Lammey said WebCentral wasn't the only company affected.
He declined to say who else had suffered outages, but said at least one telecommunications company was involved.
He said WebCentral didn't know why the water pumps had failed, but would investigate the issue in conjunction with building management.