The national water regulator has slapped a compliance notice on one of Queenstown's water treatment plants, after reports of people in Queenstown falling ill for weeks.
There are now 17 confirmed cases of cryptosporidium in the area, and a boil water notice is in place.
The water regulator, Taumata Arowai, served a compliance order on the council for its Two Mile treatment plant.
The plant doesn't have a protozoa barrier, such as UV treatment, to stop the parasite cryptosporidium entering the water supply.
The regulator says the Kelvin Heights treatment plant does have a protozoa barrier, but there are doubts that it is working.
Queenstown Lakes District Council mayor Glyn Lewers spoke to Ingrid Hipkiss.