aerial photography waterfront

Markham's water comes from Lake Ontario. It is treated in the City of Toronto and sometimes Peel Region. Water from Lake Ontario has has contaminants that can be harmful to us if we don’t clean the water. These include:

  1. Physical: materials that don't dissolve in water and make the water appear "dirty"
  2. Chemical: substances dissolved in the water from natural and manmade processes
  3. Biological: viruses, bacteria, algae, and other small living organisms (City of Toronto).

We treat water to meet the standards of the Ontario Safe Drinking Water Act, 2002. Markham’s water is monitored at all times for quality.

For a closer look at the treatment process, visit the City of Toronto website for more information.

Disinfection with Chloramine

water treatment facilityThe City of Toronto's water treatment facilities disinfect water using chloramine. It's a chemical compound that contains chlorine and ammonia.

Chloramination is the process of adding chloramine during the treatment process. This disinfects and kills microorganisms such as viruses, bacteria, and algae. Chloramine is used instead of chlorine because it lasts longer in the distribution system. It makes the water more resistant to contamination as it travels from Toronto to Markham.

Chlorine has been a safe and reliable tool for over a century. It's stopped the spread of waterborne disease. If you don't like the smell a chlorine in your drinking water, fill a pitcher and let it stand overnight in the refrigerator.


Fluoride is a mineral that occurs naturally in the environment. It's found in soil, air, and water. Fluoride is added at the end of the water treatment process to help prevent tooth decay. Many dentists and health experts want cities to add Fluoride to water. Long-term scientific studies also show that it is helpful and safe.

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