Taupō residents will have to keep observing water restrictions for another three to five days as the town copes with a massive sewage spill.
Scientists say it will take several months for pollution on the lake bed to disappear, but the sewage that flowed into the Waikato River is unlikely to pose health risks downstream.
Cambridge, Hamilton and Auckland take water from the Waikato for their town supplies, and contamination levels are being monitored.
The spill happened on Tuesday when a water main burst, creating a washout that took out the sewer. Waikato Regional Council's science manager Mike Scarsbrook told Morning Report producer Siobhan Wilson the spill was first thought to be about 190 cubic metres, but it is now estimated that 800 cubic metres spilled into the lake.