A newly upgraded water treatment plant in Horowhenua has reached its limitations and Tokomaru residents are being asked by the council to boil their water.
The boil water notice followed a week of continuous rain that muddied the Tokomaru river.
People connected to the town supply were asked to boil water for drinking, food preparation, brushing teeth and preparing baby formula.
The area's water treatment plant underwent a $350,000 dollar upgrade last year.
Horowhenua deputy mayor Ross Campbell said the treatment plant was adequate.
"But like all water treatment plants they have their limits and this one is just meeting its limit at the moment with this long length of rain and with the turbidity in the water.
"So it's working all right, the water probably tastes all right and will look all right but it's just a safeguard."