The Owhiro Bay stream, which flows into the ocean into the Cook Strait.

Wastewater from about 8000 households will be diverted into the sea off Wellington's south coast while authorities repair a leaking pipe.

It is estimated about a full-size swimming pool of sewage will end up in the sea at Owhiro Bay.

Utilities company Wellington Water said a fitting on the main wastewater pipe serving the suburbs of Brooklyn and Island Bay developed a leak in a chamber, in the car park at Owhiro Bay.

Wellington Water closed the car park on Wednesday, saying it would remain shut for at least a week to allow safe access for staff, vehicles and equipment.

READ MORE:

* Health warning after sewage-laden stormwater discharged into Wellington bay

* Wellington's dirty water revealed

* Wellington resident handed a $9400 bill for fixing failed sewer pipe

Spokesman Alex van Passen said that in order to repair the pipe, wastewater would need to be diverted through an overflow pipe into the sea at Owhiro Bay.

The volume of wastewater was too great to store or divert elsewhere, he said.

"We have explored all options, and are going to use sump trucks and other measures to minimise the amount as much as possible.