A Comprehensive Guide to PVC Pipe Fittings
That means that 1" PVC pipe will have an OD that is greater than 1", and a 1" PVC fitting will have an even larger OD than the pipe. The most important thing when working with PVC pipe and fittings is the nominal size. A 1" fitting will fit on a 1" pipe, regardless of whether either one is schedule 40 or 80.