What issue does good air gap design primarily aim to avoid?

Good air gap design primarily aims to avoid water contamination. An air gap is a vertical space between the water outlet and the flood level of a fixture, which acts as a physical barrier to prevent any backflow of contaminated water into the potable water supply. This design is crucial in maintaining the integrity of clean water systems by ensuring that there is no possibility of cross-connection where dirty water can flow back into clean water sources.

While options such as back pressure, splashed waste, and pipe blockage may be relevant issues in plumbing design, they do not relate directly to the primary purpose of an air gap. The prevention of water contamination through proper air gap design is a fundamental practice in plumbing to ensure public health and safety. Thus, the focus on establishing adequate air gaps is aimed squarely at safeguarding the drinking water from potential pollutants that could stem from reverse flow situations.