UPDATED 4.03pm: Pahiatua residents are having to boil their water for at least three days.

LISTEN ABOVE: Tararua Mayor Roly Ellis speaks to Larry Williams

The Tararua District Council's enforcing the boil water notice after test results showed a presence of E. coli in the township's drinking water.

The community's water is also being chlorinated.

Council workers are going door-to-door around homes and businesses, and all schools, rest-homes, medical centres, sports centres and day-centres have been phoned.

Tararua Mayor Roly Ellis said they won't know the extent of the contamination until tomorrow.

"We've done it as a precautionary measure. We feel that it's only right that we stamp on it straight away."

Roly Ellis said the boil water notice will remain for at least three days.

The Council said water should be boiled for drinking, making ice, food preparation, brushing teeth and preparing baby formula.

The council says people with severely compromised immune systems, infants, pregnant women, and some elderly may be at increased risk. 

It says these people should seek advice about drinking water from their health care providers.

The water supply comes from a deep bore which is not normally chlorinated.

The council said a water tank will be delivered to Pahiatua Service Centre by 5pm on Friday.

The moves come after thousands of people became sick in Havelock North from contaminated water. During that outbreak officials said E.coli can be an indicator of other bacteria in water.