Massachusetts Plumbers Journeyman Practice Exam

Where should commercial dishwashing machines discharge when located above or within five feet of a trapped floor drain?

1. Into a separate holding tank

2. Outside the building

3. Directly into the main sewer line

4. Into the inlet side of a properly vented floor drain trap

The correct answer is: Into the inlet side of a properly vented floor drain trap

The correct answer indicates that commercial dishwashing machines should discharge into the inlet side of a properly vented floor drain trap when they are located above or within five feet of such a trap. This method is essential for maintaining proper drainage and preventing backflow issues. Discharging into the inlet side allows waste water from the dishwashing machine to flow into the drainage system while ensuring that the trap retains a water seal, preventing sewer gases from entering the building. It also facilitates efficient drainage without causing blockage or backup, as the venting allows for proper airflow through the drainage system. Other methods of discharge, such as routing waste to a holding tank, could complicate the drainage process and necessitate additional maintenance. Discharging outside the building might violate plumbing or health codes, as it can lead to environmental concerns. Lastly, discharging directly into the main sewer line without the proper setup could create issues related to pressure and waste management. Therefore, using the inlet side of a properly vented floor drain trap is the most effective and code-compliant choice.