Boil water advisory in effect in Sudbury, Ont., area after coliform bacteria detected

SUDBURY – A boil water advisory is in place in Sudbury, Ont., and surrounding areas after coliform bacteria were detected in the public water supply, according to a health official. 

Public Health Sudbury & Districts is warning all residents in Sudbury, New Sudbury and Falconbridge to bring tap water to a roiling boil for at least a minute before consuming, or use bottled water. 

The agency’s associate medical officer, Dr. Emily Groot, says samples taken from two water plants came back positive for coliform bacteria, a group of bacteria found in dead vegetation and animals. 

Most coliform bacteria are not “harmful in and of themselves,” Groot says, but their presence in drinking water could indicate a larger issue.

Burgess Hawkins, a manager at the public health agency, says the boil water advisory is in place as a precaution and officials don’t believe anyone who has consumed water from the municipal system will experience negative health effects. 

Groot says the advisory, impacting a large swath of the Greater Sudbury population, is of a magnitude not seen in years – at least not since she started working in public health nearly a decade ago. 

Water advisories “are not infrequent occurrences,” Groot says, “but typically they affect smaller areas.”

She says no residents have gone to a hospital so far with symptoms consistent with drinking contaminated water.

Groot says it’s too soon to say when the advisory may be lifted and public health says it will remain in place until tests confirm the water supply is safe.

The earliest the advisory could end is Friday evening, the medical officer says, if two consecutive water tests taken 24 hours apart come back with no signs of contamination. 

That testing is being done on samples taken from the David Street Water Treatment Plant and Falconbridge Water Treatment Plant, the two facilities where bacteria were detected, Groot says. 

When routine bacteria tests came back positive at those two locations on Wednesday, it presented a bit of an anomaly.

“It’s very unusual that we would have similar results like this from two totally different treatment plants,” Groot says, noting officials are looking into the possibility that there is no contamination at all, and that there was a testing issue that resulted in a false positive.

If there is contamination, Groot says it could have potentially come from plant or animal matter entering the water supply – but the most common way this happens is when there is a loss of water pressure in the system, which doesn’t appear to be the case so far. 

News of the boil water advisory has triggered grocery store runs for bottled water, according to posts on a local Facebook group where some locals have shared photos of emptied out store shelves. 

Groot says it’s perfectly safe to drink tap water that has been boiled for at least one minute and it’s not necessary to buy bottled water. 

“The most important part is to make sure to let the water cool” before drinking boiled water, she says. “The risk is more from injury.”

Officials say the following Sudbury-area communities are unaffected and not subject to the boil water advisory: Copper Cliff, Coniston, Walden, Garson, Val Caron and area, Azilda, Chelmsford, Dowling, Skead, and Onaping.

This report by The Canadian Press was first published May 7, 2026.