Ohakune township residents and visitors are being told to boil tap water being consuming it following an issue with the water supply.
The Ruapehu District Council issued the boil water notice on Tuesday for any property connected to the drinking water supply.
Those who have consumed unboiled water in the town are advised they may not become ill, the council said on their website.
"The majority of people who unintentionally drink the water will not get sick," it said.
"At-risk groups are babies, young children, the elderly and people who have compromised immune systems.
"Please contact Healthline 0800 611 116 if you are concerned, or contact your own doctor if you start to feel unwell."
On Monday, a conserve water notice was issued after a weekend of "turbulent weather" meant the water treatment plant could not meet the demand.
The council also said reservoir stocks were depleted at 37 per cent and the water plant was operating at the maximum capacity.
Water-users are told boiling the water will kill "disease-causing" organisms.
People are advised to fill a clean metal pot with water and bring it to a rolling boil for at least two minutes.
Electric jugs with a cut-off switch can also be used as long as the jug is full.
"Boiled water should be covered and allowed to cool before use," the council said.
Adults, teenagers and children are being told they may showers with water directly from the tap as long as the water is not consumed.
For more detailed information, the Ruapehu District Council can be reached on 07 895 8188 or 06 385 8364.