What is a cross connection?

A cross connection is a piping arrangement that allows a potable water system to be connected to a source of potential pollution or contamination. It's very important to protect cross connections in order to prevent backflow into potable water. Ultimately, backflow can cause the contamination of the entire public water supply, posing a risk for anyone using water for drinking, cooking, bathing or any other purposes.

If there's an incident resulting in contamination of public drinking water (due to improper or unprotected plumbing connections), the owner responsible or occupant of the property can be held liable for damages.

What is backflow?

Backflow occurs when the normal direction of flow is reversed from it’s intended direction in any pipeline or plumbing system; backflow can be solid, liquid or gas. There are two types of backflow: backsiphonage and back pressure.

Backsiphonage backflow is negative pressure in the supply piping system causing a vacuum or partial vacuum. This causes non-potable water to be drawn back into the potable water supply.

Backpressure backflow occurs when the downstream pressure from a non-potable water source becomes greater than the pressure of the main water source. This can be the result of an increased downstream pressure caused by pumps or heat expansion from boilers or it can be the result in potable water pressure caused by firefighting, line flushing or breaks in the main water line.

Preventing backflow

To comply with Canadian Standards Association, the National Plumbing Code of Canada and the City of Edmonton Bylaw #17698, property owners must do the following to prevent backflow:  

• Remove any unnecessary cross connections and isolate your water system from the public's.

• Protect cross connections that can't be eliminated with an approved backflow prevention device or assembly.

• Ensure that all testable backflow preventers are tested annually by a certified tester, and all non testable devices are visually inspected.