The Dunedin City Council has lifted a nearly six-month "do not drink" notice for water supplies in Waikouaiti, Karitane and Hawksbury Village after lead was detected.
The decision to lift the notice, which was put in place on February 2, was made by the council and Public Health South once both were satisfied it was safe to do so, despite not confirming a cause.
But advice remains that people should flush their taps regularly.
The Ministry of Health recommends people flush a small volume of water – about 500ml – from the cold tap before using water for drinking, cooking or brushing teeth, as well as running a cold tap for about 30 seconds each morning to flush out the water sitting in pipes overnight.
"We know it’s taken time and been stressful, but we have done everything we can to ensure the wellbeing of everyone living in affected areas," Dunedin Mayor Aaron Hawkins said in a statement today.
He said the welfare of residents remained a top priority throughout the investigation into what caused the elevated lead readings.
The investigation looked at possibilities, including whether lead came from old landfills, fly tips or the nearby mine, as well as more than 2000 tests carried out across the council's water network since February 4.
However, extensive additional sampling and monitoring found there no widespread lead in the drinking water network.
Therefore, the council said the source of intermittent elevated lead levels has not been conclusively determined.
It pointed to most likely being pipes and fittings on private properties, rather than the council's water distribution network.
Dunedin City Council chief executive Sandy Graham said they decided to take a precautionary approach, though, while working with Public Health South, the Otago Regional Council, the University of Otago and other experts to understand what caused the issue.
"The drinking water that comes from our network supply is safe. However, metals, such as lead, can leach from pipes and fittings into the water if it’s been sitting overnight," she said.
"This isn’t just an issue for Dunedin – it's a national and international issue."
Meanwhile, work to replace owned water pipes with old lead fittings in Edinburgh Street and surrounding streets in Waikouaiti is now largely finished.
Water sampling in the affected areas is also continuing and there are other improvements under way, including a planned upgrade of the Waikouaiti water treatment plant, and the council will also be launching a campaign to promote the flushing of taps across the city.
"We understand it may take time for some people to feel comfortable drinking the water so a water tank will remain at each township until late August," Graham said.