Queenstown restaurant owners are angry about the delay in being warned about an outbreak of cryptosporidium in the tourist town.
Residents and businesses are being asked to boil water for drinking, food preparation, or for pets, after 15 cases of gastro sickness were reported.
The Queenstown Lakes District Council announced a boil water notice just before 7.30pm Monday on Facebook.
But some restaurants say they did not get an official email until after 9am Tuesday.
A Queenstown restaurant owner says it did not officially find out about a boil water notice for more than 12 hours.
The Queenstown Lakes District Council said there was no confirmed link that the water supply had been compromised, but it was taking a cautious approach.
But one local restaurant owner, who asked to remain anonymous, said: "From a business perspective, we're feeding hundreds of people daily as is every other restaurant in town. We should have got an email last night before anyone had any service".
All water for drinking, food preparation, dishwashing, or for pets should be boiled for at least a minute.
"We've managed to source some ice from some local supermarkets. I don't know how long that will last though. We haven't been told how long the water's going to be like this for. The ice will suffice for today as will the bottles of water that we've bought.
Operators were worried about what would happen if the boil water notice had to stick around and the impact it would have on the town's lifeblood - tourism.
'Dancing in the dark' - hotel boss
The Rees Hotel chief executive Mark Rose told Checkpoint it had been a difficult day for the team, especially since the running of the hotel depended on water.
He said he heard about the boil water notice at 5pm Monday, but the coffee machine supplier only told mentioned midday today that it should not be used for making coffees now. He wrote to council asking about using the coffee machine today, but was yet to hear back.
"It is a worry. I'm expecting overnight to get some 'please explains' from our agents overseas and I'm sure emails from guest who haven't yet arrived asking us what the situation was and how long this is going to go on for and unfortunately, we're as much in the dark as they are.
"We're really dancing in the dark."
He said hotel staff had been off work with symptoms of the bug for the past three or four weeks.
"So I would suggest it's been around for quite a bit longer than just the last week. We've had one of our managers, was off, and couldn't get out of bed for five days. It is a concern."
But, he said in this day and age the hotel should be filtering all its water.
Council and Te Whatu Ora step up efforts
Symptoms of sickness as a result of cryptosporidium could include diarrhoea, nausea and vomiting, cramps or pain, bloating, headache, lack of appetite, a light fever, tiredness or flatulence. And anyone with those symptoms was recommended to contact a doctor and not go to work or school, the government's HealthEd website said.
Te Whatu Ora is asking people who have been in Queenstown in the past 12 days experiencing a gastric upset to inform their GP.
The Queenstown Lakes District Council and Te Whatu Ora are investigating the source of the outbreak.
Queenstown Lakes Mayor Glyn Lewers told Checkpoint council had taken a "proactive, precautionary approach".
"We can't always get everyone, but obviously we put it out to all media outlets that we know, we put it onto our social media and ... I know the officers were talking with media all through yesterday evening and early this morning."
He believed council had informed businesses well.
Lewers said Queenstown was projecting the image that it was a town that was taking public health seriously.
"We only found out on Monday morning. I got my phone call between 8am and 9am if I remember rightly. So, I think we handled it as quickly as we possibly could with the information we had available to us."