Indirect drain pipe exceeding which lengths shall be trapped?

In plumbing systems, an indirect drain pipe must be trapped if it exceeds specific lengths, which helps to prevent the backflow of sewer gases and ensures effective drainage. The correct answer indicates that an indirect drain pipe exceeding 30 inches but less than 54 inches necessitates trapping.

Trapping serves to maintain a water seal in the pipe, preventing harmful gases from entering the building while also allowing for the proper discharge of wastewater. In this context, when the length of the drain is more than 30 inches, it is critical to install a trap to maintain that seal and facilitate the proper function of the drainage system. Traps are designed to hold a small amount of water, creating a barrier against gases.

The choices represent different lengths that might determine trapping requirements. However, the choice indicating 30 inches to 54 inches aligns with standard plumbing codes or practices that necessitate trapping for longer indirect drain pipes. This reflects best industry practices for ensuring sanitary conditions and the efficacy of the drainage system.