Suspicion has been cast on water quality tests that twice in two years revealed Escherichia coli bacteria in the Carterton water supply.
Hutt Valley District Health Board drinking water assessor, Scott Rostron, raised the alarm after the town supply tested positive for E coli bacteria count for a second time in two years in late May.
The first time the bacteria count was found to be non-compliant was in June last year but the water had throughout the period remained safe to drink.
Colin Wright, Carterton District Council chief executive, said tests had been clear before and after the high counts were found and there "had been a suspicion the high reading had been caused by sloppy procedures at the laboratory".
"There was no obvious reason for it to be like that and it was generally regarded as a bit of a blip."
