Wellington's pipes have failed again - this time pumping sewage into a marine sanctuary at levels 43-times higher than it is safe to swim in.

Wellington Water became aware of the contamination spike at Owhiro Bay on Wellington's South Coast just before New Year's Eve and put up signs but, with swimmers still using the water, it admits it could have communicated better.

On one hand it has told residents it is fixing the problem - likely caused by wastewater including sewage getting into stormwater - but on the other it says it is still trying to find out what the problem actually is.

Water sampling for the enterococci bacteria - found in human faeces - is done daily at four sites around the bay.

READ MORE:

* Cuba St pipe to blame for wastewater gushing into Wellington Harbour

* Bacteria levels skyrocket, as investigation into raw faeces leak into Napier harbour begins

* Kids plucked from sea north of Wellington after warning of high bacteria level

At one of those sites, where the Owhiro Stream meets the sea, the reading hit 8600 colony-forming units per 100ml of water on January 8.

Nearby readings were 7200 and 6800. Safe levels for swimming are 200 or below.

While the peak was on January 8, every day since has had one reading at do-not-swim levels.

ROBERT KITCHIN/STUFF Owhiro Bay resident Eugene Doyle wants authorities to step up efforts to fix a wastewater leak into Taputeranga Marine Reserve.

Owhiro Bay is frequently polluted with the culprit often being historic dumping at landfills up the valley leaching into the stream and on to the bay, which is part of the Taputeranga Marine Reserve.

But the latest high-readings are directly related to human waste and date back to at least New Year's Day.

Wellington Water spokesman Alex van Paassen said its was simultaneously finding and fixing the problem, as it was fixing issues it came across as it investigated up Owhiro Stream to find the main problem.

Its investigations had narrowed down to "an area we believe there is a cross-contamination".

STUFF The contamination issue is worst near the mouth of Owhiro Stream.

He would not reveal the location due to apparent privacy issues.

"I think we could have done more to communicate with the community about what was happening."

Local Eugene Doyle said people had become so blase about pollution in the bay - and signs warning of it - that they continued to swim there unaware of the heightened risk.

Wellington Water had told him that the 8600 reading came on a rainy day but Doyle pointed out that there had been high readings every day so far in 2020.

"They are big [bacteria] numbers on an ongoing basis.

ROSS GIBLIN/STUFF A dead eel found in Owhiro Stream in 2017.

"The issue for us is we want the city - Wellington Water and Greater Wellington Regional Council - to step up their efforts to resolve this."

Communication had been so lacking that some residents were unaware there was an issue.

One however was remaining on holiday out of Wellington so she could continue her daily swim.

Wastewater flowing into a marine reserve was a bad look for the regional council, Doyle said.

"If they can put our photo up on the side of a bus they can certainly do a better job of keeping our water clean."

In the lead up to Christmas Day a wastewater pipe collapsed beneath Dixon St in the central city.

By the time workers had toiled through the night on a stop-gap measure two swimming pool's worth of wastewater had leaked into the harbour.

However, part of Willis St will remain closed until at least March while Wellington Water figures out, then carries out, an enduring fix to replace the temporary pipe over the road.

After the temporary pipe was installed most of the harbour's bacteria levels returned to safe levels apart from near the lagoon and diving platforms.

The source of that contamination was tracked back to a wastewater pipe that was incorrectly attached to the stormwater system beneath Cuba St.