Which term describes the physical link between safe water and dirty water?

The term that describes the physical link between safe water and dirty water is known as a cross-connection. A cross-connection occurs when there is a direct or indirect connection between potable (safe) water and non-potable (contaminated) water. This can happen in various scenarios, such as when irrigation systems are connected to drinking water lines without proper backflow prevention devices in place.

Understanding cross-connections is crucial in food safety and public health because they pose a significant risk of contaminating the safe drinking water supply. If there's a change in pressure in the water system, it could potentially allow contaminated water to flow back into the safe water supply, leading to outbreaks of waterborne diseases.

In contrast, an air gap refers to a physical separation between the water source and the point of use, which is a method used to prevent contamination. Backflow is the undesirable reverse flow of water within a plumbing system, which can result from changes in pressure but is not the term that specifically describes the physical link itself. A foot-candle is a measure of illumination and does not pertain to water quality or safety.