It is important to be aware that even clear, odorless or tasteless water can pose a health risk. Contamination of drinking water or water shortages may arise under various circumstances, for example:
- Bursting or freezing water main
- Drought
- Flooding
- Presence of chemical products
- Parasites
- Cyanobacteria (blue-green algae)
In Québec, those in charge of drinking water distribution systems ensure the high quality of the drinking water in their network. They periodically collect water samples to make sure that the water meets the required standards 
(French only) and then take corrective action if necessary.
However, it is a good idea for everyone to be prepared in case a drinking water contamination or shortage occurs.
What to do before
Keep drinking water reserves on hand at home at all times. You should keep enough for all the members of your family and your pets.
You should have the following reserves for at least 3 days (72 hours):
- 6 litres of water per person for drinking
- 6 additional litres per person for food preparation and personal hygiene, such as brushing your teeth
- Sufficient drinking water for your pets
Make sure to have a collection of containers (empty water bottles, pitchers, large pots, etc.) that can hold drinking water in case your municipality distributes water in bulk rather than in bottles. The containers must be clean and in good condition, and should not have contained chemical products (e.g. detergents).
Also, have large-capacity containers on hand to collect non-potable water, which is useful for purposes like flushing toilets.
If the water in your home comes from a private well, be sure to have your well water analyzed regularly and disinfect it if required.
Prepare an emergency kit.
Prepare a family safety plan.
What to do during
Schools, businesses, stores and institutions must close any water fountains and notify their clientele and visitors that the water is unfit for consumption.
Food establishment operators must adopt specific precautionary measures (French only).
In the workplace, employers must provide all staff with access to safe drinking water.
In the event of a boil water advisory, boil tap water at least 1 minute at a rolling boil before drinking it.
Also use boiled water to:
- Prepare infant formula, feeding bottles and baby food
- Prepare drinks, juices, tea and coffee
- Wash fruits and vegetables eaten raw
- Prepare foods that do not require prolonged cooking (canned soups, jelly, etc.)
- Make ice cubes
- Brush your teeth and rinse your mouth
- Provide drinking water for pets. Let the water cool down sufficiently before giving it to them.
- You can store boiled water in sealed, clean containers up to 3 days in the refrigerator or during 24 hours at room temperature.
Handle the boiling water carefully to avoid the risk of burns; this warning is especially important for young children and the elderly.
If you have a domestic water filter (softener, activated carbon system, filtering pitcher, etc.), you still must boil the water before drinking it given that these water treatments devices are not designed to kill micro-organisms that may be harmful to health.
While a boil water advisory is in effect and unless otherwise notified, you can use tap water directly in the following cases:
- For food preparation and for cooking dishes which require prolonged boiling, for example, soups, pasta, potatoes, beans, etc.
- For personal hygiene and all domestic purposes, for example:
- Washing your hands, provided you use soap, wash thoroughly and dry immediately
- Taking a bath or shower, provided you do not swallow any water. It is best to scrub young children and infants with a washcloth to prevent them from swallowing water or putting toys in their mouths that have been in contact with water.
- Washing the dishes with detergent. Ensure that they are completely dry before using them. The hottest cycle of the dishwasher ensures that the water is disinfected.
- Washing clothes
If you have a water purifier that uses chloride, ozone or ultraviolet rays, it is not necessary to boil water provided that the device complies with the applicable standards, is well maintained and is in good working order. If in doubt, check with the manufacturer.
When a drinking water avoidance advisory is issued, use only bottled water or drinking water that is supplied in other ways, even if you have a home water treatment device. These devices do not provide effective protection against the contaminants in question.
Follow the authorities' instructions regarding use of tap water for domestic purposes, such as for laundry or dishes, and for personal hygiene. There may be restrictions on the use of water for such purposes depending on the contaminants in question and their concentration.
If a do not use advisory has been issued, you must use bottled water, or drinking water that is supplied in other ways, for all food-related uses, for personal hygiene and for household uses. Pay close attention to the information provided in the advisory on how to procure water.
Do not use water from your municipal water system, except to flush the toilet.
If in doubt about the quality of your tap water
If your home water comes from a drinking water distribution system
Contact your municipality or the owner of the water distribution network before drinking the water. Drinking water distribution centres regularly test their water to make sure it is safe.
If your home water comes from a private well
Have your well water tested (French only) by an accredited laboratory if you notice sudden changes in the water’s taste, odor, or appearance.
Know the health consequences
The ingestion of contaminated water can cause various symptoms, such as:
- Nausea
- Vomiting
- Diarrhea
- Abdominal discomfort
If you are experiencing symptoms, call Info-Santé at 811.
Anyone can be affected by contaminated water. However, the following are more likely to be affected, such as:
- Infants
- Young children
- Pregnant women
- The elderly
- Those with compromised immune systems
- Those suffering from a chronic disease
Note that some persons may experience no symptoms whatsoever.
What to do after
The person in charge of the water distribution network will lift the boil water advisory or drinking water avoidance advisory when:
- Test results show that the water is again in compliance with standards
- The water no longer poses a risk to users’ health
Once an advisory is lifted, take the following precautions:
- Open all cold water taps and let the water run for a few minutes before using it, to enable the complete emptying of all piping. Follow the same procedure for drinking fountains and drinking troughs.
- Empty, wash and disinfect ice machines.
- Flush out garden hoses and outdoor taps.
- If you have a home water treatment device, follow the manufacturer's recommendations. However, it is not necessary to drain a hot water tank.
Last update: February 26, 2024
