Contamination or shortage of drinking water

Last updated July 29, 2023

What are the risks of a drinking water contamination or shortage in Montréal? What measures does the city take to inform and assist residents in the event of a disaster? Find out what you need to know.

Water contamination

The city performs regular tests to ensure the quality of drinking water distributed through its water supply system. Although the city takes every possible precaution, its drinking water can still become contaminated for various reasons:

  • water main break
  • flooding
  • presence of toxic products
  • bacteria, viruses and parasites
  • blue-green algae (cyanobacteria)

Water shortage

A water main break, defective equipment, drought or even significant water contamination can lead to a drinking water shortage. Be ready to respond rapidly by preparing an emergency kit. In the event of a longer lasting shortage,  the city distributes water to residents to meet their essential needs until the resumption of normal services.

Advisories to residents

In the event of a water contamination or shortage, an advisory is distributed to concerned residents, depending on the  situation: 

  • boil-water advisory
  • water service interruption
  • do-not-consume advisory
  • do-not-use advisory


The city issues an advisory concerning the resumption of normal services once the water is safe to drink again.

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