Definitions:

1. Nominal Size: This is the approximate size used for identification (e.g., 1/2" pipe doesn’t mean the OD or ID is exactly 0.5 inches). It’s a standardized label.

2. Outside Diameter (OD): This remains consistent for a given nominal size and is the measurement you’d use when selecting fittings.

3. Inside Diameter (ID): This varies slightly due to manufacturing tolerances but is critical for determining flow capacity in plumbing or irrigation applications.

4. Wall Thickness: The difference between OD and ID reflects the wall thickness, which increases with larger sizes to maintain structural integrity under pressure.

5. Source: These measurements align with industry standards from organizations like ASTM (American Society for Testing and Materials) and are commonly referenced in PVC pipe specification charts from suppliers like Charlotte Pipe