What is a threaded fitting?

A threaded fitting is a type of plumbing or piping fitting that has external or internal threads designed to connect two or more pipes or fittings together. Threaded fittings are commonly used in plumbing, industrial, and commercial applications to join pipes and fittings together securely and allow for easy disassembly and reassembly.

External threaded fittings, also known as male threaded fittings, have threads on the outside of the fitting and are designed to be screwed into a female threaded fitting. Conversely, internal threaded fittings, also known as female threaded fittings, have threads on the inside of the fitting and are designed to accept a male threaded fitting.

Threaded fittings can be made of various materials, including brass, steel, stainless steel, copper, and plastic. They come in different shapes and sizes, such as elbows, tees, couplings, nipples, and plugs, to accommodate various piping configurations and applications.


Threaded fittings are available in different thread types and sizes, including NPT (National Pipe Thread), BSP (British Standard Pipe), and metric threads. NPT is a commonly used thread type in the United States, while BSP is commonly used in Europe and other parts of the world. Metric threads are used in many industrial and hydraulic applications.

To install a threaded fitting, the pipes or fittings being connected must be prepared by cutting and deburring the ends, then threaded with a suitable threading tool. The threaded fitting is then screwed onto the threaded pipe or fitting until it is snug, using a pipe wrench or similar tool to tighten it. Teflon tape or pipe dope may be applied to the threads to provide a better seal and prevent leaks.

Threaded fittings are typically used for low pressure applications, such as water supply lines, air lines, and gas lines. For high pressure or high temperature applications, welded or flanged connections may be preferred.

 Threaded fittings are versatile and have several advantages over other types of fittings. One of the primary advantages of threaded fittings is their ease of installation and disassembly. They do not require any special tools or equipment to install, and they can be easily removed for maintenance or repairs.

Another advantage of threaded fittings is their flexibility. They can be used to connect pipes and fittings of different materials, sizes, and shapes, making them suitable for a wide range of applications. They also allow for easy modification and expansion of piping systems, as additional fittings can be added as needed.

Threaded fittings are also cost effective and readily available, as they are produced in large quantities and can be found at most hardware stores and plumbing supply outlets.

However, there are also some limitations to using threaded fittings. They are not suitable for high pressure or high temperature applications, as they can potentially leak under these conditions. They also have a tendency to loosen over time due to vibration or thermal expansion, which can result in leaks or pipe failure.

Threaded fittings are a reliable and widely used method for joining pipes and fittings in a variety of low pressure applications.

 In addition to their advantages and limitations, there are some important considerations to keep in mind when using threaded fittings:

  1. Threaded fittings should be made of compatible materials with the pipes they are being connected to. For example, brass fittings should not be used with galvanized steel pipes, as this can cause galvanic corrosion.

  2. The size and type of threads should be carefully matched to ensure a proper seal. Using mismatched threads can result in leaks or damage to the fittings.

  3. Proper installation is crucial to prevent leaks and ensure a secure connection. The fittings should be tightened firmly but not over tightened, which can damage the threads or cause the fitting to crack.

  4. Regular inspection and maintenance of threaded fittings is important to ensure their continued reliability. This includes checking for leaks, monitoring for signs of corrosion or wear, and tightening fittings as needed.

  5. If threaded fittings are being used in an application with high vibration or movement, it may be necessary to use additional measures to secure the fittings, such as using a pipe strap or anchor.

Overall, threaded fittings are a versatile and reliable method for joining pipes and fittings in low pressure applications. However, it is important to carefully consider the materials, size, and type of threads being used, and to properly install and maintain the fittings to ensure their continued performance.