Which code violation is related to venting fixtures?

The correct answer focuses on the importance of proper venting for plumbing systems. Venting is essential because it allows air to enter the plumbing system, which prevents negative pressure and allows wastewater to flow smoothly through the drainage system.

When solid waste and gas waste are vented together, it can lead to significant problems, such as the risk of cross-contamination and the potential for sewer gas to escape into the building. This presents not only a concern for hygiene and proper function but also poses health risks to the occupants. Therefore, building codes typically require that solid and gas wastes be vented separately to ensure safety and efficiency in the plumbing system.

In contrast, the other options misinterpret the regulations or lack relevance to the specific actions necessary for safe venting practices. For instance, venting underground is not a common requirement for venting fixtures; rather, it is typically done above ground. Mixing materials in a vent can lead to corrosion and compatibility issues, but it's not as foundational to safety as the separation of solid and gas waste. Lastly, while using non-metallic materials can be a concern under certain conditions, such as temperature and pressure limits, it does not directly pertain to venting practices themselves.

Thus, the separation of solid and gas