What is a cross connection in plumbing?

A cross connection in plumbing refers specifically to any direct or indirect connection between a potable (drinking) water supply and a non-potable source that could allow for contamination. This definition is crucial because cross connections pose significant health risks; if the non-potable source becomes pressurized, it can lead to backflow, pulling contaminants into the drinking water supply. Understanding this risk highlights the importance of proper plumbing design and the implementation of backflow prevention devices to protect public health.

The other options don't accurately describe a cross connection. For instance, a connection between two potable supplies does not involve contamination risk, while a combination of different water sources doesn't inherently imply a risk to potability. Similarly, a type of plumbing fitting is a general term that does not specifically address the concept of contamination or backflow associated with cross connections.