Boil Water and Drinking Water Advisories

Please find information about Boil Water Advisories (BWAs) and Drinking Water Advisories (DWAs) below.

What is a Boil Water Advisory?

A Boil Water Advisory (BWA) is a public announcement telling people to boil their water.¹ A BWA is a safety measure issued to protect the public from bacteria or other organisms that may be in the water.

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Why would a Boil Water Advisory be issued?

The Medical Officer of Health for a health unit issues a Boil Water Advisory (BWA) when the public’s water source is not safe for drinking or other uses.  

Typically a BWA is issued because contamination of the drinking water with waterborne microbes (tiny organisms) is found.  Decisions to issue a Boil Water Advisory are based on microbial standards from the Ontario Drinking Water Quality Standards (O. Reg. 169/03).²

A Boil Water Advisory may also be issued during the following situations:

• Community outbreaks of bacteria (e.g. E. coli), viruses or parasites
• Water main breaks
• Low disinfection of drinking water
• Flooding

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What should I do during a Boil Water Advisory? 

If a Boiling Water Advisory (BWA) has been issued, it is important that you and your family properly boil or treat all the water in your home. During a BWA, it is not safe to use water directly from your tap. Only boiled or treated water should be used for drinking, preparing food, making beverages or ice cubes, washing foods, or brushing your teeth.¹

View specific guidance for individuals impacted during a boil water advisory for information on how to boil tap water and extra precautions to take during waterborne disease outbreaks.

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What to do after a Boil Water Advisory

The Boil Water Advisory will be lifted when the Health Unit’s Medical Officer of Health is sure that the water is safe. This will follow laboratory testing showing that the water has no signs of contamination. This may take several days depending on the requirements set by the Ontario Ministry of Health or the Ontario Ministry of the Environment, Conservation and Parks.

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Drinking Water Advisories (DWAs)

• What is a Drinking Water Advisory?
• Why would a Drinking Water Advisory be issued?
• What should I do during a Drinking Water Advisory?
• What to do after a Drinking Water Advisory

What is a Drinking Water Advisory?

A Drinking Water Advisory (DWA) is a public announcement issued by a health unit telling people to use an alternate water source, such as bottled water. A DWA is a safety measure issued to protect the public from chemical contamination that may be in the water. 

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Why would a Drinking Water Advisory be issued?

The Medical Officer of Health for a health unit issues a Drinking Water Advisory (DWA) when the public’s water source is not safe for drinking or other uses. 

Typically a DWA is issued because there is evidence of chemical contamination in the drinking water.  Decisions to issue a Drinking Water Advisory are based on chemical standards from the Ontario Drinking Water Quality Standards (O. Reg. 169/03).²

A Drinking Water Advisory would be issued during situations when boiling the water will NOT get rid of the problem.  If there is chemical contamination in the water, boiling the water will actually INCREASE the concentration of chemical in the water! It is not safe to drink this water.

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What should I do during a Drinking Water Advisory?

If a Drinking Water Advisory has been issued, it is important that you and your family do not use water from your tap for drinking, preparing food, making beverages or ice cubes, washing foods, or brushing your teeth. It is not safe to use water from your tap. Instead, use safe sources of water, such as bottled water and commercially treated water.

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What to do after a Drinking Water Advisory

The drinking water advisory will be lifted when the Health Unit’s Medical Officer of Health is sure that the water is safe.  This will follow laboratory testing showing that the water has no signs of contamination. This may take several days depending on the requirements set by the Ontario Ministry of Health or the Ontario Ministry of the Environment, Conservation and Parks.

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