The higher level of manganese detected in a sample of the Napier city's water is not an immediate health risk, say Napier City Council staff.
The council said the water supply in the city was safe, despite the higher levels of manganese found in a sample from a Napier home.
One News has reported a lab test of discoloured water from a Napier tap showing manganese at a level of 3.5 mg/L. The maximum level set by the Ministry of Health is 0.4 mg/L.
The city's source water, like most source waters around the world, had manganese in it in very low levels, the council's director of infrastructure John Kingsford said.
He said the higher sample that had been publicised was a sample of discoloured water that had sediment in it, which was biofilm that had built up on an inner pipe, and which manganese settled in.
The council did routine cleaning and flushing programmes of the pipes, which dislodged the biofilm, and sometimes it got dislodged more quickly, which lead to dark brown water coming out of people's taps.
Mr Kingsford said the sample that was used would have had lots of sediment in it, which had manganese in it at far higher levels than the rest of the drinking water supply.
He said one litre of the water that was tested had about the same amount of manganese per litre as a litre of tea.
Mr Kingsford said residents were not drinking the discoloured water that had sediment in it.
He said the water system had been upgraded over winter, which had changed the way water was pumped, and water moving in the network in different directions had also caused discoloured water.
People who had brown water should run the tap for 15 to 20 minutes and if that didn't fix the problem, they should call the council.