What is a plumbing cross-connection?

A plumbing cross-connection refers to an improper link between the potable water supply and non-potable sources, which can lead to contamination of the drinking water system. The correct answer highlights the mix of water supply piping and drain piping as it indicates a direct connection where contaminated water could flow back into the clean water supply, thereby presenting health risks.

In essence, the cross-connection represents a potential backflow situation where pollutants can enter the drinking water system, making it crucial to identify and eliminate these connections in plumbing systems to ensure the safety and quality of potable water. Recognizing that this scenario can cause significant health hazards reinforces the importance of proper plumbing design and installation practices.

The other answers do not accurately describe a cross-connection. While hot and cold water mixing at the faucet or the laundry sink might occur, those scenarios do not imply the same risk of contamination associated with a cross-connection. Likewise, a properly plumbed situation would ensure there are no cross-connections, aligning with plumbing codes aimed at maintaining water safety.