Markham's Backflow Prevention By-law 2012-27 (PDF), is designed to minimize potential contamination of Markham's drinking water caused by backflow incidents at cross connections.

The Backflow Prevention Program (PDF) identifies cross connections deemed at risk, and removes or isolates them at water customer buildings or facilities.

The By-law applies to:

• All industrial, commercial, and institutional properties.
  
• All multi-residential buildings and structures (For example: Condo buildings, Rental apartment buildings, Townhouse complexes with bulk water meters, etc.)
  
• Single residential properties with: fire protection. lawn sprinkler, or any auxiliary water supply
  systems.

The program requires:

• A “Cross Connection Control Survey” report for each facility. You need to complete this report every five years or when there is a change of property usage.
  
• A “Testing and Inspection” report for each backflow preventer. You need to do this at installation and each year after that.
  
• That all backflow prevention deficiencies identified through the survey or testing reports be fixed.
  
• That all backflow prevention work is done by the Qualified Persons* registered with the City.

* A Qualified Person is a private contractor with the qualifications set out in Markham’s Backflow Prevention By-law.