Queenstown's Two Mile UV filter has been installed and is awaiting sign-off from regulator Taumata Arowai.
Subject to that, the boil water notice that part of the Wakatipu has had to adhere to since September 18 may be lifted tomorrow.
The notice followed several confirmed cases of the protozoa Cryptosporidium and initially covered all properties serviced by the Queenstown Lakes District Council’s supply from Sunshine Bay to Frankton, Hanley’s Farm and Kelvin Heights.
Ultimately, more than 60 cases were confirmed, though it had never been confirmed it was spreading through the water.
Queenstown Lakes District Mayor Glyn Lewers said testing had continued "and we’ve never actually had a positive test for Cryptosporidium in the water".
While the notice was lifted for Kelvin Heights, Frankton and Hanley’s Farm on October 5, it had remained in place everywhere else.
The UV reactors had been installed and were operational, live network reservoirs had been inspected and cleaned and he expected flushing of the local network to be finished yesterday.
He said the total cost of the temporary fix, its permanent replacement — being made overseas — and upgrades to the west Wānaka, already half-finished, and Luggate plants was about $10.8 million.
The Two Mile UV filter had cost about $1.4m, he said.
"We’re looking at getting them all done before June 2024."
There were two intakes which would be deferred, including Glenorchy. That was because it was a bore-water source, meaning the council had more time to sort it out.
While Mr Lewers appreciated it had been "a right annoyance", there was a silver lining to being "the first mover in the country".
"We’ve pretty much taken all the UV disinfection out of the market.
"Other councils will be paying [premiums] because the regulator put a letter out [saying] any surface-water intake, a protozoa barrier has to be installed by [the end of] 2024 — that’s 26 councils.
"They [the regulator] have put an enormous strain on the market, the water service industry and the supply chain.