Mayor Valérie Plante's decision to put more money into the city's crumbling pipes and sewers is being welcomed by a prominent expert on the matter, even if residents aren't happy about the tax hike that will help pay for the upgrades.

Sarah Dorner, the Canada Research Chair in source water protection, said improvements to the city's water infrastructure are long overdue.

For years, she said, the problem was largely ignored.

"Nobody wants their street dug up. There are disruptions to service, so it's not something that people are eager to do," Sarah Dorner, an associate professor of civil, geological and mining engineering at Polytechnique Montréal, said this week on CBC Montreal's Homerun.

"But there has been a lack of investment in the past and if we don't catch up, we're just pushing the problem further down the road."

The increase to the water tax, which contributed to an average 3.3 per cent jump in the tax rate for homeowners, isn't sitting well with residents. Commercial tax rates also went up by an an average of three per cent.

But the city's water infrastructure — including reservoirs, water mains and treatment plants — "urgently needs major investments," according to budget documents.

A Montreal firefighter wades through a flooded street after a major water main break in 2016 The Plante administration says improvements to the water infrastructure will help prevent such incidents. (Leah Hendry/CBC)

'Game of catchup'

The city is facing a $3.5-billion water infrastructure maintenance deficit, according to the Plante administration. An estimated 11 per cent of the city's $30 billion in assets require major investments in the short-term.

"The projects are numerous, complex and expensive, but they are necessary," a budget document states.

On Homerun, Dorner said the situation has improved thanks to increased investments over the last decade.

"It's a game of catchup that we're playing," she said, explaining that other Canadian cities are grappling with similar problems.

In Halifax, for instance, the city's 2,000 kilometres of aging water and sewer pipes need $2.6 billion of work.

The federal government, which ran on a promise to invest billions into infrastructure projects, has a fund set up to cover 50 per cent of eligible costs for water-related projects.

Montreal's Jean-R. Marcotte​ treatment plant will be the world's largest wastewater facility to use ozone filtration. (City of Montreal)

From bad to better

Montreal has taken strides in recent years, Dorner said.

In the early 2000s, as much as 40 per cent of the city's treated water leaked into the ground before reaching the faucets of Montrealers, according to a recent city report.

That number was down to 30 per cent by 2016 after leaks were plugged and aging brick tunnels replaced.

It has been further reduced in the period since, Dorner said.

As well, the city is already in the process of installing an ozonization system at its Jean-R. Marcotte​ wastewater treatment plant in Rivière-des-Prairies. When finished, it will be the world's largest wastewater facility to use ozone filtration.

Ozone will reduce the risk of water-borne viruses and bacteria and cleanse traces of cosmetic and pharmaceutical products and industrial waste.

The provincial and federal governments are covering the bulk of the $98.5-million upgrade, announced in 2015.

And Montreal's infamous sewage dump was necessary in part to replace aging wooden components of an interceptor sewer.

All these investments, Dorner said, should be viewed as signs of progress — though much remains to be done, including replacing the lead pipe service lines leading to many residential homes.

"It's nothing something you can solve instantly," she said.