What is the purpose of an air gap in plumbing for dishwashers?

The purpose of an air gap in plumbing for dishwashers is to prevent backflow of contaminated water into the appliance. An air gap is a physical separation between the water supply and the dishwasher's drain line, ensuring that wastewater cannot siphon back into the clean water supply. This is an important safety feature, as it helps to maintain the health of drinking water by preventing cross-contamination.

In residential plumbing, this design effectively protects against potential hazards that could arise from back pressure, which could push dirty water back into the dishwasher and compromise the hygiene of the dishes being cleaned. Having an air gap is often a code requirement in many regions to ensure that plumbing systems are safe and effective.

The other options do not accurately reflect the purpose of an air gap. Increasing water flow, reducing noise levels, and facilitating drainage of excess water are not functions served by an air gap in the context of dishwasher installations.