A day after the Glenorchy community vociferously opposed the chlorination of its water supply this summer, a boil-water notice was put in place.
At Thursday's full Queenstown Lakes District Council meeting six residents addressed the council during public forum, outraged the council had decided to chlorinate the water supply without consultation and speaking about the quality of their ''beautiful'' water, which they did not want to see ruined by a chemical.
The residents were told it was an ''irreversible'' decision, made to protect the health of residents and visitors.
Less than 24 hours later, routine testing of the town's water supply detected E. coli.
In a statement, council chief engineer Ulrich Glasner said about 180 households were affected.
''Advice from Public Health South is that all residents and businesses should boil water as a precaution,'' Mr Glasner said.
''The scheduled implementation of chlorination will be in place next week, and testing will continue until we are satisfied there is no risk to the local community.
''We will undertake daily testing, but the boil water [will] stay in place until further notice.''
Council chief executive Mike Theelen said it was ''unfortunate timing'' coming the day after the council meeting.
''However, this reaffirms council's decision to begin chlorination next week and should act as a reminder that bacterial infections such as this can occur at any time in untreated water supplies.''
Council engineers would be investigating the source of the contamination.