What is the term used to designate the approximate inside diameter of pipe, conduit, or tube?

The term "Nominal Pipe Size" is used to designate the approximate inside diameter of pipe, conduit, or tube. This term indicates a standardized measurement that allows for consistent specifications across various applications and manufacturers. Nominal sizes do not represent exact measurements but provide a rough guide to the size of the pipe, making it easier for installation and interoperability between different plumbing components.

Using nominal sizes simplifies the selection process for pipes and fittings, as they can be categorized into common sizes that most professionals will recognize. It is particularly important in plumbing and piping systems where accurate fitting and connections are crucial.

While "Nominal Diameter" might seem similar, it lacks the widespread recognition and established use of the term "Nominal Pipe Size" in the plumbing industry. "Standard Pipe Measurement" and "Piping Specification" do not specifically refer to the approximate inside diameter, making them less appropriate in this context.