What is backflow in plumbing?

Backflow in plumbing refers specifically to the flow of water back into potable supply lines from unintended sources. This phenomenon can occur when there is a change in pressure in the water supply system, which can cause contaminated water from various sources to reverse its intended flow and enter clean water systems. Understanding this concept is crucial for maintaining the safety and quality of drinking water, as backflow can result in serious health hazards due to the potential contamination of potable water supplies.

The other options do not accurately define backflow. The forceful removal of liquid from a drainage system pertains to drainage or siphoning activities rather than the reverse flow of water into supply lines. The discharge of excess water from a fixture is related to overflow or drainage issues, but does not reflect the critical issue of backflow into drinking water supplies. Elevation of pressure in a water supply system pertains to pressure issues but again does not capture the essence of backflow, which is characterized by unwanted reverse flow that could compromise water quality.