A relief-valve pipe terminating into a water leak catch pan is not permitted, because the pan is not an ________.

The correct choice highlights the importance of plumbing codes and the proper disposal of waste. A water leak catch pan is not considered an indirect waste receptor because it lacks the necessary design to safely and effectively handle wastewater or leak water into a drainage system.

Indirect waste receptors are specifically designed to receive wastewater or similar materials and direct them to a proper drainage system without risking contamination of the water supply or creating hazards. They are typically constructed to prevent backflow, allowing wastewater to drain away safely while preventing any possible syphonage of contaminants back into the clean water supply.

In contrast, options such as indirect air receivers or direct waste outlets do not accurately describe the intended function of a leak catch pan, which is not designed for the effective management of wastewater. A primary drainage system is focused more broadly on how wastewater is collected and transported away from a dwelling, rather than the specific role of a catch pan. This distinction reinforces the significance of adhering to plumbing codes that prioritize safety and proper waste management practices.