Backflow Prevention

What is Backflow?

Backflow is defined as the reversal of the normal direction of flow in drinking water lines. This can be caused by water main breaks, fire fighting situations or other changes in water pressure. Backflow can draw dangerous substances through the drinking water system. This can result in the migration of contaminants to the taps of local residents.


How does Backflow Prevention work?

Valves are installed called backflow prevention devices, this will stop the reversal of flow from a facility or device. This effectively prevents dangerous chemicals from entering the water supply.

How is Backflow Prevention enforced?
In order to progressively address backflow prevention, the City of St. Thomas implemented a backflow prevention program under By-law No.44-2000. This program provides protection of the drinking water distribution system helping to ensure safe, clean drinking water.
Are there penalties for not complying?
Failure to act in accordance with the By-law No.44-2000 will result in termination of water service until compliance is met. The City of St. Thomas also holds the right to enforce a fine under the provincial offences act. If an incident does occur provincial charges of causing or permitting a substance to enter a drinking water system that interfere with the normal operation of the system are substantial. 
How often does a Backflow Prevention device need to be tested?

Devices need to be tested annually.

What if I don’t have annual testing done or my device fails?

Backflow prevention devices that do not pass annual testing will be considered incomplete until notifications of a passed device are received by the city. Ignoring a malfunctioning Backflow prevention device or tampering with a device may result in termination of water service until a passing device has been installed and tested.

Who can test or install a device?

Any certified plumber or anyone certified by the OWWA can perform tests and install devices. It is the owners responsibility to ensure submission of any installation or testing forms to the City of St Thomas.

How do I know what device my facility requires?

The CSA created a manual CAN/CSA-B64 to provide standards for the selection and installation of backflow prevention devices. CSA classifies facilities by Severe, Moderate and low risk. Severe risk facilities must install a reduced pressure (RP) backflow preventer. Moderate risk requires a minimum of a dual check valve assembly.  Examples of severe risk facilities include: Agriculture facilities, Industrial premise, Automotive repair, Food processing plants, carwashes, Gas stations, laundromats and many more. Refer to CAN/CSA-B64 for the entire list.

Does the City provide forms for testing?

The City of St. Thomas doesn’t have testing forms. We accept any forms with the required details of testing.

How does the Backflow Prevention program work?

The city of St. Thomas uses a data base to generate letters or emails notifying facility owners of devices due for testing. These letters will explain step by step how to proceed as far as having devices tested and who to send your completed reports to.

Who do I send my completed forms to and what is done with them?

Completed forms can be sent to the environmental coordinator for processing at [email protected].  These completed forms will be entered into the cities database which is used to ensure all devices city wide are being tested.