Fears that Taumarunui's water supply has been contaminated by sewage have been scotched by the Ruapehu District Council.
However, the council is warning all residents in the town to boil their drinking water for two minutes, and take particular care around babies, the infirm and elderly, as a precaution.
The warning is likely to stay in place until Monday. Some schools on Thursday night advised parents that they would be closed Friday due to contamination in the town's drinking water.
Locals' concerns were heightened after sewerage tankers were seen leaving the water treatment station at Matapuna throughout the day.
The Ruapehu District Council issued a notice to schools, institutions and residents to boil water before drinking it as a precaution due to "short-term operational issues" at the plant.
However, the RDC released a statement saying water filters, which are in the last step in the treatment process, were discovered by its contractor, Veolia Water, to be slowly blocking.
The problem has been identified as one of the three water filters becoming "bound up" in the processing system, the result of the small amount of carbon used as a purifying agent.
Acting chief executive Margaret Hawthorne said the problem was getting progressively worse to the point where the normal cleaning process of backwashing the filters was not resolving the issue as it should have.
This impacted on the volume of water that the plant could produce."With the impending arrival of Cyclone Lusi the decision was made to take the filters off-line to allow the plant to full the reservoirs before the bad weather hit as we cannot make water when the Whanganui River is in flood," she said.
"Taking the filters off-line changed the audited treatment process at the water plant which required it, under the Health Act, to issue a precautionary boil drinking water notice."
The council stated drinking water still remains chlorinated and the warning to boil water is just a "precautionary" measure while the filters were cleaned.
The sewerage tankers are removing sludge build up from the water ponds behind the holding tanks as yet another precaution in anticipation of this weekend's heavy rain forecasts.
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