A sudden call on Glenorchy's water supply almost ran the town's reservoir dry on Sunday night and the cause remains a mystery.
Residents in the town, at the top of Lake Wakatipu 45 minutes' drive from Queenstown, were warned to fill containers with drinking water after a "massive outflow'' from its water supply.
Initial suspicions were an open fire hydrant or a burst main.
Yesterday afternoon Queenstown Lakes District Council chief engineer Ulrich Glasner said he still did not know the cause.
"We're just hoping to get feedback from the community.''
The council warned residents at 8.15pm of a "significant and unexplained'' draw of about 20-30 litres a second on the town's water supply.
A message posted on the community's website said if it was not identified and resolved the town would likely be without water by 9pm.
Mr Glasner said council contractors Veolia shut down the town's falling main.
A bypass - installed 12 to 18 months ago - was used to supply the community directly from the bore while the reservoir filled up again.
When the falling main was opened again no high flow was observed.
"From 9 o'clock onwards everything was fine,'' Mr Glasner said.
"That's really bizarre.''
Camp Glenorchy general manager Steve Hewland said Veolia visited the construction site on Sunday night and found no issues.
"It's been well understood for many years that the storage capacity in the Glenorchy system is too small for the volume.''
The council should be congratulated for installing the bypass a few years ago, he said.
The construction of Camp Glenorchy - a multimillion-dollar project bankrolled by United States philanthropists Paul and Debbi Brainerd - began in October and is expected to open early in 2017.
Glenorchy Motors owner Dave Smith said there was some "rumbling'' in the town yesterday about what happened.
"I don't think there's any major problems with it; it's just the demand has outstripped the supply.
"It's been dry as hell and everyone's been trying to keep lawns and that alive and the scheme can't keep up with it.''
