Understanding PVC Pipe Sizes

Understanding PVC Pipe Sizes
When shopping for plumbing parts, PVC pipe sizing can be confusing. Unlike many other products, PVC pipe sizes don’t match their outside dimensions. Instead, PVC follows Nominal Pipe Size (NPS) rules, which are based on the inside diameter of the pipe. This means a 1" PVC pipe will actually measure larger on the outside. Both Schedule 40 and Schedule 80 PVC share the same NPS sizing, so fittings are interchangeable. The difference is in the wall thickness: Schedule 80 has thicker walls for added strength (mainly for high pressure industrial installations), while Schedule 40 offers a larger inside flow area. A lot of reefers will use Sch. 80 PVC for the "Grey" color, but may not realize that they are loosing flow due to the smaller inside diameter. For the highest flow rates, we recommend Sch. 40 PVC. 

These charts below will help explain these differences and how PVC pipe is sized. 

Schedule 40 NPS Diameters: