New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

How can you easily determine the outer diameter of a type K, L, or M tube?

1. Subtract 0.125

2. Add 0.125

3. Multiply by 2

4. Divide by 2

The correct answer is: Subtract 0.125

To determine the outer diameter of a type K, L, or M tube, it is essential to understand the nominal pipe sizing system used in plumbing and piping. In the context of these tube types, the outer diameter is standardized. For copper tubes, the nominal size is typically given, but the actual outer diameter needs to be known for proper fittings and connections. In this case, the standardized outer diameter for type K, L, or M copper tubing can be easily calculated by subtracting 0.125 inches from the nominal size. For example, if the nominal size is 1 inch, the actual outer diameter would be 1 inch - 0.125 inches = 0.875 inches. This consistently applies across standard nominal sizes, allowing for easy identification of the needed dimensions for fittings and installations. Thus, the process of subtracting 0.125 inches effectively gives you the correct outer diameter required for installation and compatibility.