Value Brand 5P551 Coupling 3/8" FNPT Malleable Iron Class 150

3/8" Malleable Iron Coupling

The Value Brand 5P551 coupling joins two 3/8" FNPT threaded pipes in a straight line. Made from malleable iron rated to Class 150, it suits water, air or oil lines in residential and light-commercial plumbing. The female threads on both ends accept standard NPT pipe nipples or fittings. New condition ensures clean threads and no prior stress.

Installers needing a 3/8" straight connector

This coupling fits only 3/8" FNPT threads; it will not join larger or smaller pipe sizes, nor will it adapt to compression, flare or push-fit connections. Builders who need a reducing coupling, a union for frequent disassembly, or a different material such as brass or stainless steel should select another fitting.

Thread sealant and a wrench are all that is required

Apply PTFE tape or pipe dope to the male threads before tightening to prevent leaks. Over-tightening can crack the malleable iron body, especially on smaller 3/8" sizes. Ensure the pipe ends are clean and cut square so the threads engage fully without cross-threading.