Joining Method Threaded

Image provided by Ferris State University


A threaded pipe connection involves an internal threaded fitting and an external threaded piece of pipe or other fitting, which are screwed together. Threaded pipe and fittings taper at a rate of 3/4 inch per foot, so that as the fittings are tightened, the joint become progressively tighter for a leak-free seal. The American Society of Mechanical Engineers (ASME) National Pipe Thread Taper (NPT) provides thread standards for pipe sized from 1/16- to 24-inch. The standards include parameters including threads per inch (thread density) and thread length. In practice, pipe larger than 4-inch is rarely threaded as the weight of larger pipe make it difficult to align and friction of the threads requires significant pressure to screw the pipe together. 

The fitting materials, which are used to make threaded joints with standard piping materials, are: cast (gray) iron, malleable iron, ductile iron, cast copper, brass, plastic, and steel.  Cast, malleable, and ductile iron fittings are the most widely used and are compatible for use with nonferrous piping materials such as brass, copper, and plastic. Steel fittings are usually specified for high-pressure and high-temperature applications. The most commonly used threaded plastic piping materials are PVC, CPVC, and PVDF.


Relevant Materials And Systems

Polypropylene (PP) Pipe

Manufactures and Suppliers Participating in OPUS