How is a cross-connection defined in plumbing?

A cross-connection is defined as a physical connection between a potable water supply and a non-potable source. This definition is crucial in plumbing because it highlights a potential pathway for contaminants to enter the drinking water supply. When there is a direct link between safe drinking water and water that may be unsafe—like wastewater or chemicals—the risk of backflow increases. Backflow can occur due to changes in pressure and can lead to contamination of the drinking water.

Understanding cross-connections is essential for maintaining public health and ensuring safety standards are upheld in plumbing systems. Proper plumbing practices involve implementing backflow prevention devices and ensuring that cross-connections do not occur, further emphasizing the importance of distinguishing between potable and non-potable sources.

The other options do not accurately capture the specific definition of a cross-connection. For instance, a union of two drainage systems does not pertain to the interaction of potable and non-potable supplies, and a backflow prevention assembly is a method to safeguard against the very issue cross-connections present. An emergency shutoff mechanism, while important for plumbing systems, does not relate directly to the definition of a cross-connection either.