Which method is specified for connecting indirect waste from appliances?

The correct method specified for connecting indirect waste from appliances involves using an air gap. An air gap is a physical separation that prevents wastewater from flowing back into the potable water supply. This design is crucial for maintaining health and safety standards, as it effectively eliminates the risk of contamination by ensuring that any potential backflow does not occur.

When appliances, such as sinks or dishwashers, discharge wastewater indirectly, it is essential to use an air gap in the system to allow for proper drainage while also safeguarding the clean water supply. The air gap creates a barrier that is mandated by plumbing codes to protect against cross-connections, which can lead to serious public health issues.

In contrast, connecting to a floor drain, using a siphon system, or routing through a grease trap has specific limitations and does not provide the same level of protection against backflow contamination as an air gap does. Each of these alternatives might serve specific functions in certain plumbing scenarios, but they do not satisfy the code requirement for indirect waste connections designed to safeguard the potable water supply effectively.