A cross connection is the actual physical connection between potable (drinking) water and any substance of questionable quality. A cross connection commonly occurs when a water hose is left running, yet is submerged in a tree well or in a bucket of soap water. If a backflow event were to occur, these substances could enter the drinking water supply and possibly be distributed throughout the distribution system where numerous consumers would be exposed to these substances.
What is Backsiphonage?
The positive flow of water can be reversed when there is a sudden reduction in water pressure in the distribution system, such as during firefighting or when a water main breaks. This can create a suction effect, drawing the non-potable substance into the potable water system.