What defines a cross connection in water systems?

A cross connection is specifically defined as a physical connection between potable (drinking) water and non-potable water sources. This definition highlights the critical concern in water systems: the potential for contamination. When these two types of water come into direct contact, it creates a risk for the safe drinking water supply, as non-potable sources can contain harmful substances or microorganisms that could endanger public health.

In practical applications, cross connections can occur in various situations, such as when irrigation systems, which may use reclaimed water or other non-potable water, are improperly connected to a potable water supply. These scenarios necessitate stringent regulatory oversight and the implementation of backflow prevention devices to safeguard against the unintended flow of contaminated water into the potable supply.

Given this context, the focus is on the interaction between drinking water systems and those that do not meet the purity standards for safe consumption. Thus, the correct answer effectively captures the essence of what a cross connection entails in water systems. Other choices do not pertain to this crucial aspect of water safety, as they discuss different types of connections that do not directly address the risks associated with potable water contamination.