Connecting a potable source of water and a non-potable source of water in the same line is called

• A. Backflow
• B. Cross connection
• C. Parallel service
• D. Dual supply

Answer: (B)

A cross connection is created when a potable water line is joined with a non-potable source. This setup creates a potential pathway for contaminants to enter the clean supply if pressure changes cause backflow. Backflow is the actual reverse flow of water into the potable system, which can happen when a decrease in pressure in the supply line or a pressure difference draws water backward. The cross connection term specifically describes the linkage that enables that risk, making it the best answer. Other terms refer to the flow itself or to running two supplies alongside each other, not to the connection that creates the contamination pathway. In practice, protect such points with backflow prevention devices or air gaps to keep the potable supply safe.