Action plan for cross connection control and
backflow prevention

Important information for:

  • Industrial
  • Commercial
  • Institutional
  • Agricultura
  • Residential (moderate or severe)
  • Property Owners and Occupants

In order to protect public health and the Municipal Drinking Water System, The City of Sarnia is implementing a Backflow Prevention Program and By-law to control and protect cross connections.

What is a cross connection?

A cross-connection is “any actual or potential connection between a potable water system and any source of pollution or contamination” (CSA, 2011).  cross-connection control, or Backflow Prevention, help to ensure our drinking water is protected.

How can contamination occur?

Back flow

Back flow is the reversal of the normal flow of water. Backflow can push or pull non-potable water inside the pipe from the customer‟s premises back into the municipal drinking water system. Backflow occurs when back pressure or backsiphonage conditions occur in a water line.


Backsiphonage can cause backflow if there is a drop in pressure or a negative pressure in the water line, such as a main break.

Back Pressure

Back Pressure can cause backflow when a source of pressure, such as a pump, creates a pressure greater than the one supplied by the municipal drinking water system.

Liability and Responsibility
of owners and occupants

Liability and Responsibility
of owners and occupants required under the By-law will include but are not limited to:

  • Report any knowledge of a backflow incident occurrence.
  • Perform a backflow prevention survey, every five years, to identify hazards associated with each water service connection and the type of backflow protection needed.
  • Install, repair and maintain all backflow prevention devices
    required under the by-law.
  • Obtain a plumbing Permit from the City’s Building Department for
    installation of device and inspection of
    work completed.
  • Annual testing of backflow prevention devices by a certified tester and  submit test report to the City.
  • Ensure all properties are protected via ‘Premise Isolation’.

Premise Isolation” means separation of the water supplied to  private properties from the ‘Municipal Drinking Water System’,  via installation of backflow prevention device after the water meter.



How to protect drinking water systems from backflow?

Install a suitable backflow prevention device that is testable approved by the Canadian Standards Association (CSA) B64 10 Standards.

A backflow prevention device is designed to allow water to flow in the normal direction but to stop water from flowing in the reverse direction.

TESTABLE Backflow Preventers

***Consult with a Contractor who is Certified to obtain a complete list of available backflow preventers.

Program Foundation

In order to protect the public’s health and drinking water quality, the Ministry of Environment and Climate Change enforces the ‘Safe Drinking Water Act’. The Act enforces a statutory responsibility on water purveyors to show due diligence with respect to maintaining and protecting drinking water quality.

The goal of this program

  • Inform and educate property owners on backflow prevention.
  • Identify properties that require a backflow prevention device where potential contamination of the municipal drinking water system may occur.
  • Maintain a database of certified backflow prevention device testers who are authorized to complete selection, installation and testing of devices.
  • Insure devices required under the by-law are being maintained and in good working order.
  •  Active compliance with the City of Sarnia, Backflow Prevention By-law.

NOTE: Fire protection and possibly other systems will require additional consultations to ensure adequate pressure is maintained prior to installing a backflow prevention device.

Providing Sarnia residents with safe drinking water is OUR responsibility,  keeping it safe is EVERYONE’S.

To learn more about Sarnia’s Backflow Prevention Program,
please contact:

Engineering Department
Public Works
651 Devine Street
Sarnia ON Canada N7T 1W9