Sch 40 PVC couplings are used to join two pieces of pipe. Couplings come with socket or threaded ends. Sch 40 PVC couplings also come in a range of sizes as well as reducing sizes. You can use couplings to reduce a PVC line so that you can regulate the flow and pressures in the PVC line or system. Couplings meet ASTM D 1784 and ASTM D 2466 standards and are suitable for potable water service.