The City of St. John's is fixing an enormous leak that is wasting millions of litres of treated water — enough to supply several subdivisions.

A benign-looking pothole marker had been the only sign of trouble on Austin Street, where the city discovered that a broken main is losing almost 1.5 million litres of water every day. The leak is in a business park near the Avalon Mall.

Public works manager Paul Mackey said the loss is especially wasteful because it has all been treated, and pumped from Bay Bulls-Big Pond.

Public works manager Paul Mackey says it will take a couple of weeks to fix a broken water main on Austin Street. (CBC )

"You're putting in all that energy, which costs a lot of money — hydropower and treatment costs. So it's expensive, relatively expensive water [and] that works out to about $147,000 a year," Mackey told CBC News.

To put things in perspective, the lost water would be enough to supply 1,800 households.

Or, in less than a week, the leak would be able to fill all of the pools in the Aquarena at least three times over.

The city does not always fix every leak it discovers, but Mackey said this one was too large to ignore.

"We don't think we will find many of this magnitude. Typically what you find is a lot of smaller leaks," he said.

"It's not only the work for the pipes, it's all the disruption. The street has to be reinstated, businesses have to be disturbed, and shut off. There's a whole bunch of factors."

City council voted Monday night to approve a contract for the fix, which should be done in a couple of weeks.

Meanwhile, the city will replace several dozen metres of pipe that is likely heavily corroded.