Drinking water

Last updated April 10, 2024

What should you do if you notice a change in your tap water? What types of advisories inform residents of the steps to take in the event of contamination or a service interruption? Learn everything you need to know about drinking water in Montréal.

In order to provide quality drinking water, the city carries out regular tests at its six water treatment plants:

  • Atwater (Sud-Ouest)
  • Charles-J.-Des Baillets (LaSalle)
  • Dorval
  • Lachine
  • Pierrefonds
  • Pointe-Claire 

In spite of the precautions that are taken, changes in drinking water are occasionally observed. Maintenance work on the water supply system can also require service interruptions and affect the water’s appearance.


Tap water can sometimes appear white, grey, yellow, brown or orange in colour. Several potential causes can come into play. Ton find out what to do, read our article.

Pink or black stains may appear on your toilet, sink or shower. They are caused by common bacteria, such as Methylobacterium and Serratia Marcescens, that are harmless to people in good health. However, it is recommended to clean these stains with gentle detergent, disinfect with bleach, rinse well and let dry, as well as ventilating rooms to avoid excess humidity.

Taste and smell of water

The taste and smell of water vary throughout the year. When the temperature is higher in a body of water, the algae that live in it multiply, including a species that releases a molecule which causes an earthy taste. The water treatment process eliminates all traces of algae, but the taste and smell can persist for some time in the distribution system until the water that circulates through it has been renewed. This situation presents no danger to health.

Water hardness

The type and origin of minerals in the soil determine water hardness. The total hardness of water distributed across the island of Montréal can be viewed in drinking water quality reports.

Decrease in water pressure

Various factors can contribute to a decrease in water pressure. They include work operations in progress and the presence of rust in water mains. Residents can contact 311 to report a problem. Corrective measures will be applied as required.

Water service interruptions

The drinking water supply is sometimes interrupted during work operations on the supply system. These interruptions are usually of short duration. In the event of a more prolonged water service interruption, residents will be notified about measures taken to provide them with drinking water.

Notices to residents

The city is sometimes required to issue warnings concerning drinking water consumption in the event of work operations, a breakage, defective equipment or water contamination. Lawn watering bans may be issued. The instructions to follow are outlined in advisories distributed to residents.

A notice is issued when regular services are restored, and new guidelines for drinking or using tap water are provided.

The city issues five types of advisories:

Water fluorination

The Pointe-Claire and Dorval are the only plants on the island of Montréal that distribute fluoridated water.

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