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

The term 'cross-connection' in plumbing specifically refers to the connection between two different systems, particularly where a potable (drinking) water supply could potentially mix with non-potable (contaminated) water. This situation is significant because it poses the risk of backflow, where contaminants may be drawn into the clean water supply, leading to serious health hazards. Understanding cross-connections is essential for maintaining safe plumbing standards and ensuring public health, which is why cross-connection control is a critical aspect of plumbing codes and regulations.

The other options address different plumbing concepts. A connection to a drain line focuses more on waste disposal systems rather than the risks associated with backflow between water supplies. A malfunctioning fixture pertains to issues with individual plumbing devices that are not operating properly, while a type of fixture installed incorrectly deals with installation errors, both of which do not capture the unique implications of a cross-connection.