Backflow Prevention Program

Under the City's Water By-law 2005-200, commercial, institutional, industrial and large multi-level residential property owners must install backflow prevention. 

 What is backflow?

The term "backflow" refers to the reversal of the normal direction of water through a water line. Any connection between the drinking water supply and a non-potable source is called a cross-connection. If backflow were to occur, contaminants can be introduced into the drinking water supply through these cross-connections and be distributed to users elsewhere in the system.


How does backflow occur?


Backflow can occur in two ways, backsiphonage and backpressure.

Backsiphonage can occur when there is a significant drop in pressure in the main distribution pipes which can pull water back into the system from any nearby connections. The drop in pressure is caused by a large volume of water being removed from the system, for example due to fire fighting or a watermain break. An example of this is a garden hose left in a pool, if a backsiphonage event were to occur, the pool water could be pulled back into the watermain and delivered to the tap of a nearby business or residence.

The second way backflow can occur is by backpressure. This is when the pressure on the customer's side of the connection is greater than that in the City's distribution system and pushes water back into the system.


What can be done to protect against backflow?


There are various types of backflow prevention devices available. The type of device appropriate for a particular application is determined by the degree of contamination risk. A plumber certified as a Backflow Prevention Specialist can assist in selecting the proper device.


Who is responsible?


Under the Ontario Building Code, new construction projects are required to have backflow prevention. The City of St. Catharines has initiated the Backflow Prevention Program to enhance provisions in the Water By-law 2005-200 to ensure existing commercial, institutional, industrial and large multi-level residential facilities will also have backflow prevention installed. The owner of a facility deemed to be a backflow risk must install appropriate backflow devices for premise and source isolation.

Premise isolation is the installation of backflow prevention at or near the water meter, prior to any other connection to the water service for the facility. This protects the City water distribution system from possible contamination. Source isolation is the installation of backflow prevention within a facility to isolate a cross connection from the internal water distribution system. This protects people within the facility.


How will the program be implemented?


The program will run in phases according to business type and the associated backflow risk. Initially, City staff will contact high risk businesses to have a survey of their property completed, at the owner's cost, by a plumber certified as a Backflow Prevention Specialist.


This survey will identify any existing backflow risks to the water distribution system and recommend the appropriate backflow device(s) for installation. Once completed the survey must be submitted to the City's Operations Division located at 383 Lake St., St. Catharines.

A cross connection survey must be completed every five years to ensure the facility continues to have the required backflow prevention in place.

New installations of backflow devices as recommended through the cross connection survey must be performed by a licensed master plumber. Plumbing permits are required and are available from Building & Development Services located at City Hall, 50 Church St. The City must be notified when installations are complete as a Plumbing Inspector will attend the site to inspect the completed work.

Certain backflow devices must be tested upon installation and then yearly thereafter to ensure they are functioning correctly. The testing must be completed by an OWWA certified tester who must complete one of the following report forms per device test. Copies of the completed report form will be provided to the property owner and the Operations Division.  

Device tags are to be attached to each device and must be signed and dated by the tester. Tags are available from Building & Development Services and the Operations Division.

Please view our list of companies that can perform backflow surveys, installations and device testing:






Garden Hose
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