What is an acceptable reason to use an air gap in plumbing systems?

Using an air gap is primarily accepted in plumbing systems to provide maximum backflow protection. An air gap is a physical separation between the end of a water supply line and the overflow level of a receptacle, such as a sink or a basin. This design prevents contaminants from entering the drinking water supply by ensuring that there is no direct pathway for water to flow back into the potable water system in the event of a backflow.

Backflow can occur due to various reasons, including changes in water pressure, which could potentially allow non-potable water to siphon back into the clean water supply. The air gap serves as a critical barrier, ensuring that any potentially contaminated water cannot re-enter the plumbing system, thereby protecting public health and maintaining water quality. It's a crucial element in plumbing codes and safety regulations, especially in residential and commercial applications where cross-contamination could pose serious health risks.

While considerations like cost, installation ease, and water usage are important factors in plumbing design, they do not provide the same level of health and safety assurance that an air gap does in protecting against backflow. Thus, choosing to incorporate an air gap is fundamentally tied to the goal of ensuring the integrity of the water supply.