New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

Is it true that an 8 inch tube has an outside diameter equal to an 8 inch pipe?

1. True

2. False

3. Depends on the material

4. Only in specific applications

The correct answer is: False

An 8-inch tube does not have the same outside diameter as an 8-inch pipe because the two are measured differently. In plumbing and piping, the term "pipe" typically refers to the nominal diameter, which is a standardized size that does not correspond directly to the actual measurements. An 8-inch pipe, for instance, generally has an outside diameter that is larger than 8 inches due to the wall thickness, which varies depending on the pipe's schedule (which indicates the wall thickness of the pipe). Conversely, an 8-inch tube, which is usually of the thin-walled variety, actually has a nominal size that reflects its true outside diameter—approximately 8 inches. Thus, the outside diameter of an 8-inch tube will be approximately 8 inches, whereas the outside diameter of an 8-inch pipe is greater than 8 inches. This difference highlights crucial concepts in plumbing and piping standards, leading to the conclusion that the statement is indeed false.