Repairs to sewerage systems mean human waste that was going into the Christchurch estuary since February, is now flowing into the Christchurch wastewater treatment plant.
Christchurch City Council says testing has shown the amount of overflow from sewers being pumped into city waterways has almost halved in the last two months.
Further repairs to around 11km of pumps and pipes will be completed in about a month.
Water and waste manager Mark Christison says the repairs will further reduce the sewerage levels in waterways.
The council hopes to allow people to use the city's beaches again during summer.