What is the best definition of a cross-connection in plumbing?

A cross-connection in plumbing is best defined as a plumbing water distribution pipe connected to a contaminant source. This definition accurately highlights the critical concern that arises with cross-connections: the potential for contaminants to enter the potable water supply.

When a potable water line is connected to a non-potable source—such as irrigation systems, chemical tanks, or even an improperly installed bathroom fixture—there is a risk that water can flow backward into the clean water supply. This backflow can occur due to various factors, such as changes in pressure, creating health hazards due to the potential contamination of drinking water.

Understanding this definition is crucial for ensuring safe drinking water and effectively preventing the health risks associated with contaminated water supplies. Cross-connections must be identified and mitigated through proper plumbing practices, including the installation of backflow prevention devices where necessary.