NCCER Pipefitter Certification Practice Test

The inner diameter of 10-inch schedule 80 piping is 9 5/8 inches. Schedule 80 pipes have thicker walls than schedule 40 pipes, which reduces the inner diameter more significantly. When referencing pipe dimensions, it's important to understand that the nominal size (such as 10 inches) does not directly translate to the actual inner diameter due to variations in wall thickness.

In this case, schedule 80 piping typically has an inner diameter that is standardized at 9 5/8 inches. This size is crucial for pipefitting and system design as it affects flow rates, pressure drop calculations, and compatibility with fittings and valves. Knowing the correct inner diameter helps ensure proper installation and system performance.