A restriction on any non-essential water use has been put in place with immediate effect this morning for Pōrangahau residents.
A Central Hawke's Bay District Council spokesman said their team discovered a "critical" issue with the Porangahau water supply.
Residents have been told to stop all non-essential water use immediately and restrict other use.
"Non-essential use means water use for drinking, hygiene and sanitary needs only. A total ban on outdoor use is in immediate effect," the spokesman said.
"This issue does not relate to the quality of water (it's not a boil water notice) and relates only to the supply and volume of water available."