Inch (Imperial) PVC Fittings and Valves
Inch (also termed Imperial) pipe sizes ARE NOT size compatible with metric pipe systems, plumbing or waste pipe sizes. The inch size refers to an "approximate bore" of the pipe (it's an old system that has been adopted from one which originated with steel pipe in the 1800's!), not the actual measurement of either in internal or external diameter of the pipe or fitting. For tables giving details on the exact sizes see our technical document.