When selecting the right connection for pipes and tubes, two popular fitting types come up: Compression fittings and NPT (National Pipe Thread) fittings. Both serve to secure pipes together but have distinct characteristics, advantages, and applications.
Today, we’ll dive deep into compression fitting vs NPT, comparing their structures, common sizes, and appropriate use cases. We’ll also explore if these two can be used interchangeably, and provide guidance on how to choose the right one for your project.
If you have any questions or doubts, feel free to reach out to us at Dingfeng for tailored solutions.
What is an NPT Fittings?

NPT fittings are widely used in plumbing, gas, and hydraulic systems. These fittings feature a tapered thread design that ensures a tight, leak-free seal when two parts are screwed together. The seal is created by the wedging action of the threads as they tighten.
Structure and Features
NPT threads are conical, meaning they get tighter as they are screwed together. This allows them to form a more secure seal. Typically, the thread angles are 60 degrees, and the threads are designed to fit precisely into one another to prevent leaks.
Common Sizes of NPT Fittings
Below is a chart of common NPT fitting sizes:
Size | External Thread Diameter (inches) | Pitch (Threads per Inch) |
---|---|---|
1/8″ NPT | 0.405″ | 27 |
1/4″ NPT | 0.540″ | 18 |
3/8″ NPT | 0.675″ | 18 |
1/2″ NPT | 0.840″ | 14 |
3/4″ NPT | 1.050″ | 14 |
1″ NPT | 1.315″ | 11 |
Applications and Characteristics
- Application Areas: Used in water, gas, and air systems, where high pressure and leak-free performance are crucial.
- Characteristics: Reliable, reusable, provides a strong seal under pressure, easy to install.
What are Compression Fittings?

Compression fittings are designed to join two pipes or tubes together with the help of a compression nut and a ferrule. These fittings are typically used in applications where plumbing systems need to handle both liquids and gases at different pressures.
Structure and Features
Compression fittings work by tightening a compression nut around the ferrule, which then presses down on the pipe to create a seal. The main components include:
- Compression Nut: A hexagonal nut that tightens the seal.
- Ferrule: A small ring that compresses the pipe to create a leak-tight seal.
- Body: The fitting body where the pipe is inserted.
Common Sizes of Compression Fittings
Compression fittings come in various sizes, commonly for smaller-diameter pipes. Some of the most common sizes are:
Title | Nominal Size | Tube OD (mm) | Ferrule ID (mm) | Nut Length (mm) | Maximum Working Pressure (bar) |
---|---|---|---|---|---|
Mini Compression Fitting | 1/8″ | 4 | 3 | 15 | 160 |
Standard Compression Fitting | 1/4″ | 6.35 | 5.5 | 20 | 140 |
Large Compression Fitting | 1/2″ | 12.7 | 11 | 25 | 120 |
Extra-Large Compression Fitting | 3/4″ | 19.05 | 17 | 30 | 100 |
Applications and Characteristics
- Application Areas: Common in plumbing, refrigeration, and heating systems.
- Characteristics: Ideal for tight spaces, easy installation, durable, and leak-resistant when properly tightened.
Compression Fitting vs NPT: Key Differences
Let’s break down the differences between NPT and Compression fittings in various aspects:
Compression Fitting vs NPT: Thread Type
- NPT: Features tapered threads that help create a strong seal through compression as they are screwed together.
- Compression: Uses a nut and ferrule system, relying on mechanical compression to create a tight seal around the pipe.
Compression Fitting vs NPT: Seal Type
- NPT: The seal is formed through the threads themselves, making it ideal for high-pressure systems.
- Compression: Relies on the ferrule being compressed around the pipe to form a seal, better suited for lower pressure systems.
Compression Fitting vs NPT: Installation

- NPT: Requires precise alignment of threads to ensure a leak-free connection. It can be more challenging to install in tight spaces.
- Compression: Easier to install, especially in confined areas, as it doesn’t require threading or the application of force to the pipe.
Compression Fitting vs NPT: Reusability
- NPT: Can be reused multiple times if not damaged during installation or removal.
- Compression: Ferrules may become deformed with multiple uses, reducing reusability.
Compression Fitting vs NPT: Strength and Pressure Handling
- NPT: Excellent for high-pressure systems, especially for liquid or gas pipelines.
- Compression: While good for low to moderate-pressure applications, compression fittings may not hold up well under extreme conditions.
Can NPT and Compression Fittings Be Used Interchangeably?
One common question is whether NPT fittings can be swapped with Compression fittings. The answer is generally no. While they may seem similar at first glance, there are key differences that make them incompatible for direct interchange.
Differences in the Sealing Mechanism
The most significant difference is how the seal is created. NPT fittings rely on the tapering of threads to create a tight seal, while compression fittings depend on the compression of a ferrule to secure the pipe. These differing methods mean that a Compression fitting cannot be used directly with an NPT connection, and vice versa, without an adapter.
Adaptors
To use these two types together, a special NPT to Compression fitting adapter is required. These adapters are designed to combine the tapered threads of NPT fittings with the compression mechanism of a compression fitting, allowing them to work together.
How to Choose between Compression Fittings and NPT Fittings?

Step 1: Identify the Application
The first step in choosing between compression and NPT fittings is to clearly define the application. If it’s a plumbing project in a residential or commercial building where the pipes are made of copper and the installation needs to be quick and easy, compression fittings might be a good choice.
On the other hand, if it’s an industrial application with high-pressure fluid transfer, such as in a refinery or a chemical plant, NPT fittings are likely more suitable due to their ability to withstand higher pressures.
Step 2: Consider the Pressure Requirements
If the system will operate under high pressures, NPT fittings are generally a better option. Their tapered-thread design and the use of sealants can handle higher pressures compared to compression fittings.
However, if the pressure is relatively low to moderate, compression fittings can be sufficient, especially if they are installed correctly. For example, in a low-pressure water supply system in a small building, compression fittings can provide a reliable connection.
Step 3: Evaluate the Pipe Material
The type of pipe material can also influence the choice of fitting. Compression fittings are versatile and can be used with a variety of pipe materials, including copper, brass, and plastic.
If the pipes are made of a material that is not easily threaded, like some types of plastic, compression fittings might be the only practical option. NPT fittings are typically used with metal pipes that can be threaded, such as steel or brass pipes.
Step 4: Look at the Installation Environment
The installation environment plays a significant role. If the installation is in a tight space or in an area where access to soldering or complex threading operations is limited, compression fittings are more convenient. They require less space for installation and do not need additional equipment like a soldering torch.
However, if the environment is such that vibrations or movement are expected, NPT fittings might be more suitable as their threaded connection can provide a more secure and stable joint.
Step 5: Consider Cost and Availability
Cost and availability are also important factors. Compression fittings are often more readily available in hardware stores and are generally more affordable for small-scale projects. NPT fittings, especially in larger sizes or made of specialized materials, can be more expensive.
However, in some industrial settings, NPT fittings might be the standard, and their availability might be higher in those areas.
Important Considerations
- Compatibility: Always check the compatibility between the two types of fittings before installation. Using an adapter is possible but should be done with caution.
- Material Choice: The material of the fitting (brass, stainless steel, plastic) can impact its durability and the types of systems it can be used for.
- Proper Installation: Regardless of which fitting type you choose, ensuring correct installation is key to a leak-free and safe connection.
Conclusion
In this compression fitting vs NPT comparison, we’ve explored the differences, applications, and best practices for each type. While NPT fittings offer a strong, pressure-tight seal, compression fittings are more suited for easy installation in tight spaces with moderate-pressure systems. Choosing between them depends on your project’s needs.
If you’re interested in our high-quality fittings, please visit our homepage or reach out to us for a product catalog. Feel free to contact us anytime for tailored solutions to fit your needs.
FAQs About Compression Fitting vs NPT
Are NPT and compression the same?
No, NPT and compression fittings are not the same. NPT fittings have a tapered-thread design with a 60-degree thread angle. The sealing is achieved through the interference of these tapered threads, often with the aid of sealants. In contrast, compression fittings consist of a nut, a ferrule, and a body.
The sealing is accomplished by the compression of the ferrule onto the pipe when the nut is tightened. The sizing systems are also different; NPT fittings are sized based on the nominal pipe size (approximate inside diameter), while compression fittings are sized according to the outer diameter of the pipe.
Their applications also vary, with NPT fittings being more suitable for high-pressure and industrial applications and compression fittings being popular for copper pipe plumbing and areas where easy installation is required.
Are JIC and NPT compatible?
JIC (Joint Industrial Council) and NPT fittings are not directly compatible. JIC fittings are similar to AN fittings, with straight threads and a flare seal. NPT uses tapered threads that rely on the deformation of the threads to create a seal.
What is the difference between compression and threaded fittings?
The main difference lies in their sealing mechanisms. Threaded fittings, like NPT fittings, rely on the interference of their threads to create a seal. In the case of NPT, the tapered threads play a crucial role in achieving this seal. Sealants are often used to enhance the seal. Compression fittings, on the other hand, use a ferrule that is compressed onto the pipe by tightening a nut.
The ferrule deforms to create a seal around the pipe. The thread on the nut of a compression fitting is mainly for the mechanical action of tightening, not for sealing directly. Another difference is in sizing. Threaded NPT fittings are sized based on the nominal pipe size, while compression fittings are sized according to the outer diameter of the pipe. Installation processes also vary, with threaded fittings often requiring more skill in terms of thread alignment and torque control, while compression fittings are relatively easier to install.
What is compatible with NPT?
NPT fittings are compatible with other NPT fittings, and they can be used with sealants or tape for water-tight seals. Adapters are available to connect NPT to other fitting types.
What thread is AN?
AN fittings have straight threads, which are used to create a seal with the help of washers or O-rings, unlike NPT, which uses tapered threads.
Where to buy fittings?
For custom fittings, you can contact us at Dingfeng. We offer a full range of fittings for all applications, from NPT to AN, and we are happy to assist you with any specific needs. Feel free to reach out for our product catalog.