Drinking water normally flows in one direction, from the town's water system to your taps. A change in water pressure in the water main (usually caused by a water main break or an activity like firefighting) can cause water to flow backwards, from a plumbing service back into the drinking water. This is called backflow.
Backflow can only occur where there is a cross connection. Examples of cross connections include:
Are Cross Connections Dangerous?
Cross connections between water supplies and sources of contamination are one of the most significant threats to the health of the water supply.
How Can Backflow be Prevented Where Cross Connections are Present?
Backflow prevention devices must be installed between a plumbing service and the town's water main whenever a cross connection is present. Property owners and occupants are responsible for:
Ensuring backflow prevention devices are installed where required by the National Plumbing Code of Canada; and
Ensuring backflow prevention devices are tested annually.
Find out more about cross connections and backflow prevention: