Which statement correctly describes how pipe and tubing are dimensioned?

Which statement correctly describes how pipe and tubing are dimensioned?

• A. Pipe is dimensioned by its nominal size and schedule while tubing is identified by the outside diameter and wall thickness
• B. Pipe and tubing are both dimensioned by outside diameter and wall thickness
• C. Pipe uses nominal size and schedule; tubing uses its nominal size
• D. Both use nominal size and schedule

Answer: (A)

Sizing pipe and tubing uses two different systems. For pipe, the size is given as a nominal size plus a schedule. The nominal size is a rough reference that doesn’t match the actual outside diameter, and the schedule tells you the wall thickness (and thus the internal passage and pressure rating). For tubing, the size is specified by its actual outside diameter and its wall thickness, so fittings and performance line up with those precise measurements. That combination—pipe with nominal size and schedule, tubing with outside diameter and wall thickness—is why this statement is correct.

Sizing pipe and tubing uses two different systems. For pipe, the size is given as a nominal size plus a schedule. The nominal size is a rough reference that doesn’t match the actual outside diameter, and the schedule tells you the wall thickness (and thus the internal passage and pressure rating). For tubing, the size is specified by its actual outside diameter and its wall thickness, so fittings and performance line up with those precise measurements. That combination—pipe with nominal size and schedule, tubing with outside diameter and wall thickness—is why this statement is correct.