What is defined as a physical connection between a public water supply and a questionable source?

A cross connection is defined as a physical connection between a public water supply and a questionable source, which poses a risk of contamination. This type of connection can allow harmful substances from the questionable source to enter the public water supply system, potentially endangering the health and safety of consumers.

Understanding cross connections is vital in water supply management and public health, as they can occur unintentionally at various points within a plumbing system. Measures such as backflow prevention devices are often employed to eliminate or control such risks, but recognizing what constitutes a cross connection is the first step in protecting water systems from contamination.

In the context of the other options: a backflow preventer is a device installed to prevent backflow, while an air gap is a physical separation used to protect against backflow, and an interconnect generally refers to connections between two separate systems. However, none of these directly defines the physical connection that leads to a contamination risk like a cross connection does. Thus, identifying and properly managing cross connections is a critical aspect of maintaining safe drinking water standards.