What is considered a physical link that can allow contaminants to enter a potable water supply?

A cross-connection is recognized as a physical link that can allow contaminants to enter a potable water supply. This situation occurs when there is a connection between a drinking water supply and a source of contamination, which could be anything from wastewater to chemicals. If the pressure in the potable water system drops for any reason, such as a pipe break or high water usage, contaminants from the non-potable source can be siphoned back into the drinking water supply, leading to potential health risks.

Contrastingly, options like check valves and water filters serve to prevent backflow and filtration of contaminants, respectively, thereby protecting the water supply. An air gap is a physical separation between the water supply and any potentially contaminated source, which also functions to prevent contamination but does not represent a direct link like a cross-connection does. Thus, understanding the vulnerability associated with cross-connections is essential for maintaining safe drinking water systems.