What defines a "cross-connection" in plumbing?

A "cross-connection" in plumbing is defined as a temporary connection between a potable water supply and a non-potable source. This definition is critical because it highlights the potential for contaminants from the non-potable source to enter the potable water supply if there is a reversal of flow, often due to changes in pressure. Understanding this definition is essential for maintaining the integrity of drinking water safety and ensuring public health by preventing waterborne illnesses.

The other options do not accurately represent a cross-connection. For example, a connection between two potable water sources does not introduce the risk associated with non-potable sources, while a connection solely for irrigation purposes typically involves potable water used for beneficial landscaping without posing a direct risk to the supply. Additionally, a permanent pipe used for drainage does not involve a connection between potable and non-potable water sources, therefore, it does not fulfill the criteria for a cross-connection. Recognizing these distinctions helps in implementing effective backflow prevention measures in plumbing systems.