Backflow Prevention

Backflow occurs when water flows in the wrong direction, potentially allowing chemicals or other contaminants to enter the drinking water system. Changes in water pressure, water main breaks and firefighting can cause backflow.

The City of St. Thomas has a Backflow Prevention Program under Water By-law No. 44-2000 to help protect the drinking water supply.

Who needs a backflow prevention device?

Commercial, industrial and other facilities may be required to install a backflow prevention device based on the level of risk they pose to the drinking water system. Requirements follow applicable CSA standards and the Ontario Building Code.

Contact a certified plumber or qualified backflow tester to determine which device your facility requires.

Testing and maintenance

• Annual testing is required. Devices must be tested every year by a qualified professional.
• Submit test reports to the City. Property owners are responsible for ensuring installation and testing forms are submitted.
• Repair failed devices promptly. Devices that fail testing must be repaired or replaced and pass a follow-up test.

Failure to comply with the by-law may result in water service being discontinued until requirements are met.

Submitting test reports

Email completed installation and testing reports to backflow@stthomas.ca. The City records the results to track compliance with annual testing requirements.

The City accepts testing forms that include the required information; it does not provide a specific testing form.

Backflow Prevention Brochure

Learn more about backflow, how prevention devices protect drinking water, and what property owners and businesses need to know.

View the Backflow Prevention Brochure

Questions?

Contact the City of St. Thomas at 519-631-1680 or email backflow@stthomas.ca

For full requirements, refer to Water By-law No. 44-2000