Australian/New Zealand Standard 3500 defines backflow as-

1. Flow in a direction contrary to the normal or intended direction of flow.
2. The unintended flow of water or other liquids from a potentially polluted source into the potable water supply.

Where Can It Happen?

Anywhere potable water is used!

How Does It Happen?

Any liquid has the potential to flow backwards given the right conditions.

CROSS-CONNECTIONS are direct or indirect physical connections of potable water and polluted water or liquids.

BACKSIPHONAGE occurs when water flows backwards due to drop in pressure.

BACKPRESSURE occurs when the outlet pressure is greater than the supply pressure

How Serious is it?

At worst, backflow has the potential to cause death!