The pipe in question is 55 years old, according to Wellington Water.
The agency said it is organising a water tanker to supply residents with temporary drinking water.
TJ Shirtcliffe, a manager at Leuven Belgian Beer Cafe across the street, said a leak had been bubbling away in the spot for about two months, and had been reported to the council.
“The pavement has been coming up for eight weeks,” Shirtcliffe said.
He said things got worse this afternoon when it started “just spewing water”.
“The whole street was completely flooded.”
He said it flooded right up to the steps of buildings across the street from Leuven.
Social media users have taken to Wellington community Facebook page Vic Deals to share photos of the flooded street.
“Water feature on Johnston St is getting worse so you should probably move your bike!” one poster said, noting motorbikes parked in the sizable puddle.
Videos supplied to the Herald show fire crews carrying a person through the flooding on their back.
Another video shows a person rescuing their scooter by driving it through the flooded street.
In May, Wellington City Council voted to form a regional council-controlled water entity with Upper Hutt, Lower Hutt, Porirua and the Greater Wellington Regional Council.
The new entity would replace Wellington Water in line with the Government’s Local Water Done Well policy.
Hutt City Council voted to join the entity last week while Upper Hutt City Council is expected to vote on it today.
Lower Hutt Mayor Campbell Barry, who currently chairs the Wellington Water Committee, said Upper Hutt’s vote represents a reset for water services in the region.
Barry said the new model would allow for more investment in the network, not constrained to council funding.
It officially comes into force 1 July 2026.