What do all pipe classes with the same nominal pipe size have in common?

The correct answer is that all pipe classes with the same nominal pipe size have the same inside diameter. The nominal pipe size (NPS) is a standardized designation used to identify the diameter of pipes. This sizing system is based on the internal diameter, which is a crucial measurement as it determines the flow capacity of the pipe.

Although different pipe classes may have variations in wall thickness, weight, and length, the internal diameter remains consistent among pipes of the same nominal size. This consistency is vital for ensuring compatibility in systems where different types of pipes might be interconnected.

It's worth noting that while the internal diameter is uniform, different materials and manufacturing processes can lead to variations in the weight and wall thickness of the pipes. Consequently, when working with piping systems, understanding that pipes with the same nominal size will accommodate the same flow size is essential for proper system design and implementation.