While not flashy or exciting, pipe fittings are crucial to the success of plumbing systems. This is because they allow pipes to connect to form a cohesive setup. Without fittings, pipes would be unable to form a seal with each other, and liquids would not be able to flow to your faucets and fixtures. Thousands of combinations of pipe sizes, materials, and thread types demand a need for thousands of types of pipe fittings. In this article, you can learn about the most popular types of pipe fittings used in household plumbing systems, the materials used to make them, and tips on how to select the right fitting for your system.
What is a pipe fitting?
Pipe fittings are used to join plumbing components to allow for many types of configurations. They are used to either extend or change the direction of flow in a plumbing system. Pipe fittings are available in many different sizes and materials, allowing compatibility with many different types and sizes of pipe. Within a plumbing system, a pipe fitting can change the direction of the flow of liquid, extend the length of a pipe run, or change the flow rate of liquids or gases. The material, size, and type of fitting a system requires is determined by the pipe size, pipe material, the liquids used in the system, and the pressures within and outside of the system.
Types of pipe fittings
Many types of pipe fittings are used in plumbing systems, but some are used more often than others. We include some of the most popular types of fittings below. For an all-encompassing look at pipe fitting types and terms, refer to our pipe fitting glossary.
Tees
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Used for: Connecting and diverting flow through two or three pipes Tee pipe fittings contain one inlet and two outputs, one at a 90-degree angle and the other at 180 degrees. Tee fittings get their name from their resemblance to the letter “T”. These fittings are one of the most common types of pipe fittings you will find in plumbing systems. This is because tee fittings are versatile and easy to manufacture. Tee fittings can be used to divert, merge, or redirect flow in a plumbing system. |
Couplings
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Used for: Connecting two pipes from the outside A coupling is used to connect two pieces of pipe together from outside of the pipe. Couplings are usually installed as permanent connections between pipes of either the same size or different sizes. Couplings that connect two pipes of different sizes are known as reducers, and couplings that connect two pipes of different standards are known as adapters. Learn more: What is a quick-disconnect coupling? | What is a quick-connect coupling? |
Adapters
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Used for: Connecting pipes of different standards or sizes An adapter fitting is used when two pipes that must be connected do not share the same standard of connection or are not the same size. For example, one pipe may require a BSP fitting, while the other may contain NTP threads. In this situation, a BSP-to-NTP adapter would be needed with the appropriate sizes on each end. Adapters that connect two pipes of different sizes are known as reducing couplings. These couplings reduce the flow areas between two pipes without altering their diameters. |
Reducers
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Used for: Connecting pipes of different sizes Fitting reducers gradually change in diameter between one pipe and the next. These fittings are used to connect two pipes of different sizes or a pipe and fitting of different sizes. Unlike reducing couplings, fitting reducers smoothly reduce flow rate between a large pipe and a smaller pipe. |
Unions
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Used for: Connecting two pipes that must be disassembled regularly Union couplings are used to connect two pipes in systems where pipes are frequently taken apart. Unions contain a male end, female end, and a nut that is tightened to form a tight seal. Unlike a coupling, union connectors can easily disconnect from pipes by loosening the nut, making maintenance to the plumbing system much simpler. |
Elbows
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Used for: Redirecting flow Elbow fittings redirect the flow between two pipes a given number of degrees. The most common elbows are 45 and 90 degrees, but other configurations are available. Elbows come in two lengths known as short radius and long radius. Short radius elbows are commonly used in pressurized applications or when there is insufficient room for a long radius elbow. In addition to changing the direction of flow in a system, elbow adapters can be used to connect two pipes of different sizes or connection standards. |
Crosses
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Used for: Connecting and diverting flow through two to four pipes Cross fittings contain four openings, either one inlet and three outlets or one outlet and three inlets. These are commonly used in hot and cold-water systems, drainage systems, and sprinkler and irrigation systems. |
Nipples
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Used for: Connecting two female-threaded pipes Nipple fittings are used to connect two female-threaded pipes or fittings. These fittings contain two male-threaded ends that seamlessly connect to merge two pipes or fittings together. Nipples come in multiple configurations. A close nipple contains little material between both male-threaded ends, meaning little of the nipple is exposed when the pipes or fittings are connected. A hex nipple, on the other hand, contains a six-sided section between the two threaded ends for a wrench to grip. |
Valves
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Used for: Regulating or stopping flow through a system Valves are used to turn water flow on and off or adjust the flow rate of liquid or gas through a system. They come in a plethora of configurations that are each used for specific applications. While technically a type of fitting, valves are generally categorized in a class of their own. Learn more: A guide to plumbing valve types |
Caps
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Used for: Stopping flow at the end of a pipe or fitting Caps are female-threaded fittings that install on the outside of a pipe to stop the flow of liquid or gas. These can be used to stop system flow permanently or temporarily. They are added to the end of pipes during a change to a plumbing system or for any other event where flow is no longer needed. |
Plugs
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Used for: Stopping flow while protecting pipe threads Plugs, like cap fittings, are used to stop flow at the end of a pipe or fitting. However, plugs are male threaded, meaning they insert into the threads of a pipe or fitting opening instead of fixing to the outside. |
What materials are used for pipe fittings?
Pipe fittings, just like pipes, are made from a wide array of materials. The materials used in a fitting must be compatible with the material of the pipes it is connecting. As a result, fittings are made from many of the same materials as pipes. Some of the most common materials used for pipe fittings include PVC, CPVC, copper, steel, brass, ABS, HDPE, and polypropylene. When selecting the material for your pipe fitting, ensure it can handle the temperatures, liquids or gases, and pressures within your system.
How to choose the right pipe fitting
When choosing a pipe fitting for your application, you must focus on three details of your pipes: their materials, sizes, and fitting standards.
Material
The material of your pipe fitting must be compatible with the material of your pipes. As a general rule, the same material should be used for both the pipe fitting and the pipe it is connected to. This ensures that both components are well suited for the application they are used for. In cases where pipes of different materials must be connected, transition fittings are used. These fittings contain one material on one end and a different material on the other. This allows for pipes of different materials to integrate seamlessly as long as the materials are compatible with the application they are used for.
Sizes
The size of fittings is an obviously important factor in selecting the correct fittings for your system. Without precise sizing, there will be no seal, and the system will not function properly. If you need to connect two pipes or fittings of different sizes or standards, there is an adapter fitting that will suit your needs. Read below to learn more about how pipe fittings are measured.
Learn more: How to determine pipe thread type and size
Fitting standards
Pipe fitting standards are determined by a governing body to determine how pipes and fittings join together. Some of the most common pipe standards include NPT, NPTF, BSPT, BSPP, SAE, UN, and UNF. Because these standards are determined by governing bodies, they differ based on location. For example, NPT (National Pipe Thread) is the most popular US standard for tapered thread fittings. BSP (British Standard Pipe), on the other hand, is the popular standard in Great Britain, Australia, and the commonwealth countries.
The standard of fitting you need is determined by the standard of your pipes. When connecting pipes of two different standards, use an adapter fitting that is suited to your pipes’ respective sizes and standards.
Learn more: Common pipe thread types
If you have any additional questions, please do not hesitate to contact us.