The term describing the reverse flow of liquids in a plumbing system is known as?

Backflow refers to the unwanted reverse flow of liquids in a plumbing system, which can occur when there is a change in pressure that causes water to flow in the opposite direction. This can happen due to various reasons such as a sudden drop in water pressure, which may result in contaminants being drawn into the potable water supply. Understanding backflow is essential for maintaining water safety and adhering to plumbing codes, as backflow can lead to serious health risks if harmful substances enter the drinking water supply.

Other terms in the options refer to different concepts. Drainage generally refers to the process of removing wastewater from a plumbing system. Siphoning is a specific process where liquid is drawn through a tube due to differences in atmospheric pressure, but it is not an overarching term for reverse flow in plumbing systems. Infusion typically relates to introducing a substance into another substance, which does not pertain to the reversal of flow in a plumbing context. Therefore, "backflow" is the most accurate term to describe this phenomenon.