A physical cross-connection is defined as:

A physical cross-connection is identified as a connection that may allow the flow of water from an unapproved (non-potable) supply into an approved potable water supply. This definition highlights the critical concern in public health and environmental sanitation regarding the potential for contaminants to enter drinking water systems. Cross-connections pose significant risks because they can compromise the safety and quality of potable water, leading to serious health risks such as waterborne illnesses.

In plumbing and environmental health, ensuring that potable water remains uncontaminated is essential. Understanding physical cross-connections is vital for anyone working in environmental health, particularly in preventing backflow incidents where non-potable water can flow backward into clean water systems, often due to pressure changes.

Recognizing this significance helps reinforce the practices and regulations designed to protect water supplies, emphasizing the importance of proper plumbing systems and the implementation of appropriate backflow prevention devices where necessary.