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Backflow Prevention

Building Owners: Backflow Prevention A Must

Backflow Prevention DeviceAs of spring of 2008, industrial, commercial, institutional and multi-residential buildings require approved devices at water connections that prevent the risk of “backflow” into the drinking water system. For existing customers, the change will be spread out over five years with 600 customers affected each year. This will allow staff to work with the affected customers.

Customers who were required to comply in 2008 were notified by letter or contacted directly by the Development Services Department. Affected customers also received notice of a public information meeting on Backflow Prevention.

The Backflow and Cross-Connection Prevention Program forms part of the City of Thunder Bay’s Waterworks By-Law 060-2007, 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.

For further information, contact the Backflow Prevention Officer at 625-3430

Who’s Affected?

  • Industrial buildings 
  • Commercial buildings
  • Institutional buildings
  • Multi-residential buildings
  • 3,000 customers over five years

Are you a property owner affected by the Backflow Prevention Program? Click here for our new email notification option.

What is backflow?

Normally, 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. This risk can be eliminated by installing the appropriate backflow devices.

Forms, FAQs & More

our new email service for backflow prevention notices is in the works!

The Building Services Division is streamlining the notification process for the Backflow Prevention Program! We will soon be emailing notices to make it easier for property owners to receive and review the letters/renewal notices usually sent by mail. This advancement is only made possible with subscribers.

To sign up to receive your notices by email, please fill out the form below completely.


  • Receive notices for multiple properties at one email inbox
  • Have your compliance deadlines at your fingertips
  • Share notice information easily with your Certified Backflow Prevention Contractor

Subscribe to email notifications for the Backflow Prevention Program


All information is necessary so that we may verify owners and match them to their properties.


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