Program Overview

Markham's Backflow Prevention Bylaw (No. 2012-27), is designed to minimize potential contamination of Markham's drinking water caused by backflow incidents at cross connections.

The Backflow Prevention Program involves identifying cross connections (deemed at risk) and removing or isolating them (called backflow prevention) at the building or facilities of water customers.


The By-law applies to the following categories of Markham’s water customers:

  • All industrial, commercial and institutional properties.

  • All residential buildings and structures with 2” (50mm) water connections or larger.

  • 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 to be completed every five years or when there is a change of property usage.

  • A “Testing and Inspection” report for each backflow preventer to be conducted upon installation and annually thereafter.

  • All backflow prevention deficiencies identified through the survey or testing reports should be rectified.

  • All backflow prevention work should be completed by the Qualified Persons