Which statement about inlet and outlet levels in distribution boxes is true?

The statement that the inlet must be 6 inches higher than the outlet in distribution boxes is grounded in the principles of wastewater management and hydraulic design. This height difference is critical for ensuring proper flow dynamics within the system. When the inlet is higher than the outlet, gravitational force aids in the movement of wastewater from the inlet to the outlet, promoting efficient drainage and reducing the risk of backups or stagnation.

This vertical separation helps maintain adequate flow rates and minimizes the potential for clogging and other operational issues that can arise if the system is not constructed with sufficient height differences. Therefore, the requirement for the inlet to be 6 inches higher than the outlet is a standard practice aimed at promoting effective wastewater distribution in various treatment systems.

In contrast, other statements would lead to improper system functioning. For example, having the inlet and outlet at the same level could cause problems with flow and drainage, while a requirement for the inlet to be excessively higher (such as 12 inches) could complicate installation and is not typically necessary. The idea that inlet and outlet levels do not matter would also disregard the principles necessary for effective and efficient wastewater management.