All commercial, industrial, institutional and large multi-residential (five units or more) buildings must have approved backflow prevention in place to protect our drinking water from contamination.

Backflow prevention schedule

  1. Cross connection assessment done by a Certified Contractor 
    (Copies to Backflow Prevention Officer and property owner)
  2. Apply for building permit and pay $100 fee (Usually done by contractor)
  3. Contractor installs required upgrades, including testable backflow prevention devices
  4. Certified Contractor tests backflow prevention devices
    (Test report copies to Backflow Prevention Officer and property owner)
  5. Contact City Backflow Prevention Officer (807-625-3430) for an inspection to approve installations
  6. Testable devices must be tested every year by a Certified Contractor
    ($50 renewal fee applied to water bill as per Waterworks By-law 029-2018)
  7. Have a new cross connection assessment done by a Certified Contractor every five years as well as annual testing

PLEASE NOTE: As of June 30, 2019, Building Services will no longer be mailing paper copy Notices of Annual Testing. Please make note of your annual testing date. Every year, you are required to have your devices tested by a Certified Contractor. Every 5 years, you must have your cross connections assessed.

To increase efficiency and reduce waste, email reminders will be sent. Your email address and phone number are required to stay up-to-date with this mandated program. Please contact our Building Division Clerk to provide this information.

If you do not provide updated information, you will not be notified of your responsibilities. Not supplying contact information may result in non-compliance with the Backflow Prevention Program, which can lead to fines up to $100,000 and/or termination of your water service.

Backflow prevention forms

If you require a PDF in an accessible format, email our Municipal Accessibility Specialist or call 807-625-2240.

Certified backflow prevention device contractors

Only Certified contractors registered with The City of Thunder Bay can complete cross connection assessments and test backflow prevention devices. 

  • ADEPT Plumbing & Mechanical
  • Aqua North Plumbing & Heating
  • A Villeneuve Mechanical Ltd
  • B. Gibson Mechanical
  • Caledon Creek Mechanical
  • Clow Darling Ltd
  • Craig Plumbing Centre
  • Dell Mechanical Contracting
  • E. S. Fox Limited
  • JTS Mechanical Systems Inc.
  • North-Shore Plumbing & Heating
  • Proactive Water Solutions
  • Robert's Plumbing & Sheet Metal Co
  • Thermal Mechanical Systems Inc
  • Twin City Plumbing & Heating
  • Venshore Mechanical Ltd  

Contact us

E-mail our Backflow Prevention Team

Inspections of installed backflow prevention devices and technical information:
Backflow Prevention Officer
(807) 625-3430

General Program information
Building Division Clerk
(807) 625-2213

Normally, drinkable water flows from the City's distribution system into the plumbing in a building. Backflow is the reversal of that water flow direction which could allow potentially contaminated water from a private water system, such as a boiler, sprinkler system or even a sink, to be drawn back into the City water mains. Backflow can be a result of water main breaks, fire hydrant flushing or firefighting. This risk can be eliminated by installing the appropriate backflow devices.

The Backflow and Cross-Connection Prevention Program forms part of the City of Thunder Bay's Waterworks By-Law 068-2018, developed in accordance with the requirements of the Provincial Safe Drinking Water Act. This Act requires all Municipal Drinking Water Systems to address risks to the safety of the distribution system, including the risk of backflow from contaminated water. Non-compliance with the Backflow Prevention Program can lead to fines up to $100,000 and/or termination of your water service.

If you require a PDF in an accessible format, email our Municipal Accessibility Specialist.

Contact Us