It happens when pressure drops in the main, for instance during a burst or maintenance, and the resulting suction pulls water back from the property. A hose left sitting in a bucket, a pool, or a container of garden chemical is the classic example, and it is why a hose end should never be left submerged.
We Do It All!
For a burst pipe or a serious leak, turn the water off at the mains tap before you call. If water is anywhere near power points, the switchboard or light fittings, stay clear and treat it as an electrical hazard. Do not enter standing water in a room with live power.
