What does the term 'cross-connection' refer to in plumbing?

The term 'cross-connection' in plumbing refers to a connection between two different systems, particularly where potable (drinking) water and non-potable (waste) water can interact. This situation poses a significant risk if contaminants from the non-potable system can flow back into the drinking water supply, potentially leading to contamination. For example, if a hose connected to a faucet is submerged in a pool of dirty water, a cross-connection exists that could allow the dirty water to siphon back into the clean water supply. This understanding is vital for maintaining safe and clean drinking water and is a fundamental concept in plumbing codes and practices.

The other options focus on different aspects of plumbing but do not accurately describe the concept of cross-connection. A connection to a drain line, a malfunctioning fixture, and an incorrectly installed fixture all pertain to plumbing issues that may affect functionality or compliance, but they do not capture the critical health and safety implications associated with cross-connections.