A boil water notice for the Mangaore community after two dead rats were found in a reservoir supplying drinking water to the area.
The Horowhenua District Council said the rats were found during a routine monitoring using an underwater drone.
It said it carried out monthly inspections of its reservoirs, with the last testing on September 13. There was no indication of how long the two rats had been in the reservoir.
The council said about 30 to 40 properties may be affected.
The affected reservoir has been taken offline and an existing alternative reservoir is now supplying the local network.
Chief executive Monique Davidson said the council acted quickly after the rodents were discovered and is working with Taumata Arowai, the Water Services Authority.
“Our teams today have been flushing the main water network, draining any potentially contaminated water from the network, reducing the risk to having a minimal impact, however, caution still applies and that is why we’ve issued the boil water notice,” she said.
The affected reservoir will be drained, cleaned and disinfected before being refilled.
“We understand this news may be unsettling for our Mangaore residents, and we want to ensure the community are well informed about the status of their drinking water.”
The council said thorough water quality testing would be carried out before the reservoir was returned to service.
The work was expected to be completed by tomorrow afternoon.
Until the notice is lifted, residents are advised to boil water for drinking, preparing food, brushing teeth, washing fruit and vegetables, making ice and preparing infant formula.
Water could still be used for showering, bathing, laundry and flushing toilets, with young children supervised while bathing to avoid swallowing the water.