Water supplies in three North Island areas are having to be conserved or undergoing extra treatment.
Residents in Levin were told to conserve water again this morning when the town's treatment plant was closed because the Ohau river supplying it became too muddy.
The Horowhenua District Council again issued a precautionary boil water notice for Levin this afternoon.
The plant has stayed closed since this morning.
The council said the boil notice was only a precautionary notice to safeguard people if the river water did not improve.
Water services manager Paul Gaydon said people in Levin needed to conserve water as the town was running off a backup supply.
Mr Gaydon said he expected a $3 million upgrade to the council's treatment plant to be completed by the end of March.
In Napier, a third E coli test was being evaluated by officials. Residents were asked to conserve water after one of the city's major water tanks was closed at the weekend because of a positive E coli result.
Lower Hutt's water was still being chlorinated and sites tested around the city to ensure there is no E coli in the water there.
On Saturday, Wellington Water added chlorine to the water supply after a sample from the Naenae Reservoir tested positive for the bacteria.
Wellington Water spokesperson Alex van Passen said all potential points of contamination were being checked. "Our lab will also review their whole sampling process to make sure everything was carried out as it should be."
Wellingtonians were told to stay out of the water at many of the capital's beaches during the weekend after an overflow of wastewater into the harbour.
Most of Wellington's beaches are now cleared for swimming after a pollution warning at the weekend of contaminants being washed down storm water drains by heavy rain.
However the city council is still waiting for tests results on Lyall Bay where heavy rain earlier in the week caused a small overflow of wastewater at the Moa Point treatment plant.