Sodium hydroxide coming to all tap water in Thunder Bay, Ont., in 2018

The City of Thunder Bay is moving ahead with its plan to add sodium hydroxide to its water supply to reduce the amount of lead in tap water.

The chemical will be injected at the Bare Point Water Treatment Plant and flow to all homes using city water, beginning in early 2018, according to Michelle Warywoda, the director of the city's environment division.

"It's a very, very small amount, just enough to change the pH of the water, which is what is going to help us reduce the lead going into the water," she said.

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About 7,500 to 8,000 homes in ThunderBay are thought to still have older lead pipes connecting them to the city's water mains. When water sits in those so-called service pipes for a while, it can accumulate lead, eliciting readings above the Ontario Environment Ministry guideline of 0.01 milligrams per litre.

A change to copper piping resolves the problem, but the city can't force homeowners to change the connecting pipes that are on private property. So,cities across the province are looking at other ways to reduce the lead, and the associated health risks.

Sodium hydroxide is one of the chemicals approved by the Ministry of the Environment for corrosion control, Warywoda said.

The city ran a pilot study last year in Current River and found it works well with the type of water in Thunder Bay, she said.

The report on the study will be presented to city council early this fall followed by a series of public information sessions about the change, Warywodasaid.

"This is already an approved plan," she said. "Now we're just following through on the next steps."

There's no firm date in 2018 set for the injections to begin at Bare Point, but Warywodasaid it will be early in the new year.

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