What does the term 'backflow' refer to in plumbing?

The term 'backflow' specifically refers to the movement of water in the wrong direction within a plumbing system. This situation typically occurs when there is a drop in water pressure in the supply line, which can cause water to flow backward into the clean water supply. Backflow can pose significant health risks as it may allow contaminants from various sources, such as irrigation systems or wastewater, to enter the potable water supply.

Understanding backflow is crucial for plumbers because it necessitates preventative measures, such as the installation of backflow prevention devices, to protect the public water system from contamination. This concept is foundational in plumbing codes and practices to ensure the safety and integrity of drinking water.