What is a cross-connection in water systems?

A cross-connection in water systems refers specifically to a link between a drinking water supply and any source of contamination that is not approved for drinking use. This connection poses a risk because if backflow occurs—when water flows in the opposite direction from its normal flow due to pressure changes—potentially contaminated water could siphon into the potable water system.

Understanding this concept is crucial for maintaining the safety and quality of drinking water. Effective cross-connection control measures, including proper plumbing practices and backflow prevention devices, are essential for protecting public health. The other options do not accurately represent the nature of cross-connections; they either describe legitimate connections or safety mechanisms that do not pose contamination risks.