Which of the following does NOT prevent cross connection?

A hose connected to your faucet sitting in dirty water is the scenario that does not prevent cross-connection. Cross-connection occurs when a potentially contaminated source is able to flow into a clean water supply. In this case, if the end of the hose is submerged in dirty water, any back-siphonage (which can happen when there is a drop in water pressure) could draw that contaminated water back into the clean water supply, creating a significant health risk.

Using a grease trap to collect oils helps manage waste and prevent contamination of the drainage system but does not directly influence cross-connections related to water supply. The air gap between the faucet and the bottom of the sink is a critical element for preventing backflow, as it ensures that no water can flow back into the faucet from the sink. Similarly, the air gap between the drain pipe and the floor drain serves the same purpose by providing a barrier that prevents sewer water from rising up to contaminate clean water sources.

Understanding how these systems work can help ensure food safety and compliance with health regulations.