How to deal with a contamination or shortage of drinking water

Last updated July 22, 2025
Reading time: 2 min
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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? Follow our guidelines on how to stay safe and protect your health.

Risks

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.

Preparing for a shortage

A 72-hour emergency kit can help you react faster in an emergency.

Your water reserve should include:

  • Drinking water: 2 litres per person, per day.
  • Additional water: 2 litres per person, per day to prepare food and for personal hygiene (e.g.: brushing teeth).
  • Drinking water for your pet.

What to do during a shortage

Water supply and distribution

Use your water reserve wisely. 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. Go to the distribution site mentioned by the city to get your water supply.

Advisories issued

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

A map also lets residents view the area concerned by the advisory, where known. If necessary, a automated community call service is used. At all times, observe the guidelines set out in the advisories issued. The city issues an advisory concerning the resumption of normal services once the water is safe to drink again.

To receive notices by text or e-mail, subscribe to the Notices and Alerts service.

Potential symptoms

Did you drink contaminated water? Contact 811 of you experience any of the the following symptoms:

  • nausea
  • vomiting
  • diarrhea
  • stomach pain

It’s possible that you will not experience any symptoms. Drinking contaminated water can be particularly dangerous for vulnerable people: 

  • newborn babies
  • young children
  • pregnant women
  • seniors
  • people with compromised immune systems
  • people with chronic diseases

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