A new bypass pipe installed in Parnell has reduced the sewage discharged into the Waitematā Harbour but has not stopped it, Watercare says.
It has been three weeks since a waste and stormwater pipe burst under a 13-metre-deep sinkhole in a central Parnell car park.
Crews have since created a 400-metre long above-ground bypass pipe to skip the broken section and stop hundreds of litres of wastewater flowing into the ocean every second.
Watercare head of service delivery Sharon Danks told Morning Report water samples were being taken from the ocean to measure the environmental impacts of the sewage overflow.
"The pumps are running from today, it'll be a slow ramp up over the next couple of days because there's a few things that we need to do ahead of the pumps being at full capacity."
This included pumping down all of the water that was stored in the main and resolving the overflows fully.
"The sewage is still overflowing into the Waitematā right now and it will be over the next day or two but it will be with decreasing volumes as the pumps pump down."
Overflows would still occur in wet weather, she said.
"And they probably will occur more often than they occur in normal circumstances. 'Cause of the catchments being combined catchments which take a lot of stormwater as well there is always a risk of wet weather overflow in this catchment."
Danks said it was a huge milestone for Watercare that the pumps were running.
She said the underground pipe was still blocked and it was hoped this would be unblocked in the coming few weeks.
Rehabilitating and repairing a larger section of the main was likely to take about five months, she said.
