Wastewater has been flowing into the Avon/Heathcote estuary following a failure at a pump station on Monday night.
The failure at the Pages Road station was partially repaired overnight on Monday, but there is still a small overflow.
The station transfers much of the wastewater from the east of the city to the wastewater treatment plant.
The Christchurch City Council says the pipeline remains fragile and it will be several weeks before repairs are finished.
Signs with public health information and directions to keep out of the water are being put up where necessary.