Flare Fitting vs NPT: A Comprehensive Comparison 2025

Flare Fitting vs NPT

Table of Contents

When it comes to hydraulic and plumbing connections, choosing the right fitting is essential. Among the most commonly used are NPT (National Pipe Thread) fittings and flare fittings.

Today, we’ll explore the differences between: Flare Fitting vs NPT, focusing on their structure, dimensions, applications, and unique features.

By the end, you’ll understand how to choose between flare fittings and NPT fittings for your specific needs. If you have any questions about this content, feel free to contact us.

What is an NPT Fitting?

Flare Fitting vs NPT what are npt fittings

Structure of NPT Fittings

NPT fittings are threaded pipe fittings with a tapered thread design. The threads are designed to create a seal by wedging tightly together as they are screwed in. This ensures a leak-proof connection when properly sealed with thread tape or sealant.

Common Sizes of NPT Fittings

Below is a table of common NPT fitting sizes, including relevant examples:

NPT Size (Inch)Thread Pitch (TPI)Outer Diameter (Inch)Example
1/8 NPT270.4051/8 NPT flare fitting
1/4 NPT180.541/4 NPT to 3/8 flare fitting
3/8 NPT180.6753/8 NPT to 3/8 flare fitting
1/2 NPT140.841/2 NPT x 3/8 flare fitting
3/4 NPT141.05Female flare fitting to NPT
1 NPT11.51.315Flare fitting to NPT, NPT flare fitting

Applications of NPT Fittings

NPT fittings are widely used in plumbing, gas lines, and industrial applications. They are ideal for:

  • Low to moderate-pressure systems.
  • Connecting pipes and hoses.
  • Systems where a simple and cost-effective solution is needed.

Key Features of NPT Fittings

  • Tapered Thread Design: Ensures a secure and leak-proof connection.
  • Versatile: Available in various materials, such as stainless steel, brass, and plastic.
  • Simple Installation: Requires minimal tools.

What is a Flare Fitting?

Flare Fitting vs NPT Flare Fitting

Structure of Flare Fittings

Flare fittings have a unique structure. They consist of a flare nut, a flare body, and in some cases, a sleeve. The flare body has a flared end, which is created by expanding the end of a tube at a specific angle, usually 37° for inverted flare fittings (a common type).

The flare nut is used to compress the flared end of the tube against a mating surface, creating a seal. The sleeve, when present, helps to support the tube and ensure a proper fit. This design is different from NPT fittings as it doesn’t rely on tapered threads for sealing.

Common Sizes of Flare Fittings

Flare Fitting SizeEquivalent in Inches
1/16″ Flare0.0625″
1/8″ Flare0.125″
1/4″ Flare0.25″
3/8″ Flare0.375″
1/2″ Flare0.5″
3/4″ Flare0.75″
1″ Flare1″

Common Applications of Flare Fittings

  • High-pressure Systems: Such as refrigeration and hydraulic systems.
  • Fuel Lines: Used in gas and oil pipelines.
  • Aerospace and Automotive: Common in braking and transmission systems.

Key Features of Flare Fittings

  • Durability: Understand high-pressure environments.
  • Reliable Seal: The flaring process ensures a tight seal.
  • Reusable: Connections can be disassembled and reassembled without damage.

Flare Fitting vs NPT: Key Differences

Flare Fitting vs NPT npt fitting

Design

  • Thread Design: NPT fittings have tapered threads, which rely on the compression of the threads as they’re tightened to create a seal. Flare fittings, on the other hand, have a completely different design. They use a flared end that is compressed by a flare nut against a mating surface. There are no traditional threads like in NPT fittings for sealing purposes.
  • Sealing Mechanism: As mentioned, NPT fittings seal through thread compression. Flare fittings seal by the compression of the flared end of the tube. The flared end deforms slightly under the pressure of the flare nut, creating a tight seal against the mating surface.

Size

  • Nominal Sizes: While both NPT and flare fittings come in a range of nominal sizes, the actual dimensions can vary. For example, a 1/4″ NPT fitting and a 1/4″ flare fitting may not have the same outer diameter or connection dimensions. The thread dimensions of NPT fittings are based on the tapered thread standard, while flare fittings have their own set of size specifications related to the flare diameter and the size of the flare nut.
  • Compatibility: The size differences mean that you can’t simply substitute a flare fitting for an NPT fitting of the same nominal size. The connections won’t align properly, and it will be impossible to create a reliable seal.

Materials

  • NPT Fittings: NPT fittings are commonly made from materials like brass, stainless steel, and plastic. Brass is popular for its corrosion – resistance, and ease of machining. Stainless steel is used in applications where high strength and corrosion – resistance are required, such as in industrial settings. Plastic NPT fittings are often used in low-pressure applications or in systems where chemical compatibility is a concern.
  • Flare Fittings: Flare fittings are typically made from materials like copper, aluminum, and steel. Copper is often used in automotive fuel lines due to its good corrosion – resistance, and malleability, which makes it suitable for the flaring process. Aluminum is used in some applications where weight is a concern, such as in aviation. Steel flare fittings are used when high strength is required.

Applications

  • Pressure Requirements: NPT fittings are well-suited for high-pressure applications. Their tapered thread design allows them to withstand pressures of several hundred psi. Flare fittings, on the other hand, are more commonly used in low – to – medium-pressure applications. While they can create a reliable seal, their design may not be as effective in extremely high-pressure situations.
  • Industry Usage: As mentioned earlier, NPT fittings are widely used in plumbing, automotive, and industrial applications. Flare fittings are more prevalent in automotive fuel systems, some low-pressure hydraulic systems, and in the aviation industry for specific fluid transfer needs.

Structure

  • Overall Shape: NPT fittings have a more traditional cylindrical shape with threaded ends. The taper of the threads is a defining feature of their structure. Flare fittings, on the other hand, have a more complex structure with a flare nut, a flare body, and sometimes a sleeve. The flared end of the flare body is a key structural element.
  • Connection Method: NPT fittings connect by screwing the male thread into the female thread. Flare fittings connect by tightening the flare nut, which compresses the flared end of the tube against a mating surface.

Installation

  • NPT Installation Steps:
    1. Wrap threads with thread tape.
    2. Screw the fitting into place.
    3. Tighten with a wrench.
  • Flare Fitting Installation Steps:
    1. Flare the end of the tubing using a flaring tool.
    2. Insert the flared end into the fitting.
    3. Secure with a nut and tighten.
Comparison AspectNPT FittingsFlare Fittings
Thread DesignHave tapered threads, seal through thread compressionUse a flared end compressed by a flare nut against a mating surface, no traditional threads for sealing
Sealing MechanismSeal through thread compressionSeal by compression of the flared end of the tube
Nominal SizesCannot substitute flare fittings of the same nominal size, connections won’t align properlyHave your own tapered thread standard, actual dimensions vary from flare fittings
CompatibilityCommonly used in low-to-medium pressure applications, less effective in extremely high-pressureCannot substitute NPT fittings of same nominal size, connections won’t align properly
MaterialsCommonly made of brass (corrosion-resistant, easy to machine), stainless steel (high strength, corrosion-resistant), plastic (low-pressure, chemical compatibility)Typically made of copper (used in automotive fuel lines, corrosion-resistant, malleable), aluminum (weight concern in aviation), steel (high strength)
Pressure RequirementsWell-suited for high-pressure applications, can withstand several hundred psiMore traditional cylindrical shape with threaded ends, the taper of threads is a defining feature
Industry UsageWidely used in plumbing, automotive, and industrial applicationsPrevalent in automotive fuel systems, some low-pressure hydraulic systems, and aviation for fluid transfer
Overall ShapeHave your size specifications related to flare diameter and flare nut sizeA more complex structure with a flare nut, flare body, and sometimes a sleeve, flared end is key
Connection MethodWrap threads with thread tape, screw fitting into place, and tighten with wrenchConnect by screwing male thread into the female thread
Installation StepsConnect by tightening the flare nut to compress the flared end against mating surfaceTread Design

Can They Be Interchanged?

In general, flare fittings and NPT fittings are not interchangeable. The differences in design, size, and sealing mechanism make it impossible to create a proper connection.

Step 1: If you try to connect a flare fitting to an NPT fitting, the lack of compatible threads and the different sealing methods will result in a leaky connection.

Step 2: Similarly, connecting an NPT fitting to a flare fitting will not work as the tapered threads of the NPT fitting will not match the flared connection of the flare fitting.

How to Choose between Flare Fitting and NPT

Flare Fitting vs NPT (1)

Consider the Application

  • Pressure and Fluid Type:
    • Step 1: First, determine the pressure requirements of your system. If it’s a high-pressure system, such as a hydraulic system in an industrial machine, NPT fittings are likely the better choice. For example, if your system operates at pressures above 100 psi, NPT fittings can handle the load more effectively.
    • Step 2: Consider the type of fluid being transferred. If it’s a fuel in an automotive application, flare fittings may be more suitable, especially if the pressure is relatively low. However, if it’s a corrosive fluid, you need to choose the right material for either NPT or flare fittings. For a corrosive fluid, stainless-steel NPT fittings or copper-based flare fittings with appropriate coatings may be required.
  • Industry Standards:
    • Step 1: Check the industry standards for your application. In the plumbing industry, NPT fittings are the norm. If you’re working on a plumbing project, it’s best to stick with NPT fittings to ensure compatibility with other components.
    • Step 2: In the automotive industry, both flare fittings and NPT fittings are used, but for different applications. Fuel lines often use flare fittings, while some engine-related hydraulic systems may use NPT fittings. Familiarize yourself with the specific requirements of your industry.

Check the System Requirements

  • Space and Accessibility:
    • Step 1: Consider the available space in your system. Flare fittings may require more space around the connection due to the presence of the flare nut and the flared end. If space is limited, NPT fittings may be a better option as they have a more compact design.
    • Step 2: Think about the accessibility for installation and maintenance. If the connection will be difficult to reach, NPT fittings may be easier to install and service as they can be tightened with a standard wrench. Flare fittings may require a specific flare nut wrench, which can be more difficult to use in tight spaces.
  • Cost and Availability:
    • Step 1: Evaluate the cost of the fittings. In some cases, flare fittings may be more expensive due to the additional components (flare nut, sleeve) and the more precise manufacturing process. However, if you need a large quantity of NPT fittings, the cost may also add up. Consider your budget when making a decision.
    • Step 2: Check the availability of the fittings. In some areas, NPT fittings may be more readily available as they’re a common standard. In other cases, flare fittings may be easier to find, especially in regions with a strong automotive or aviation industry presence.

Key Points to Remember

  • Sealing Mechanism: NPT uses thread sealant; flare relies on metal-to-metal contact.
  • Pressure Handling: Flare fittings are better for high-pressure systems.
  • Installation: Both require proper tools and techniques for optimal performance.

Conclusion

Both NPT fittings and flare fittings have unique advantages and applications. Choosing the right one depends on your system requirements and operating conditions. If you’re interested in our high-quality fittings or need further guidance, visit our homepage or request our product catalog. We’re here to help!

FAQs About Flare Fitting vs NPT

Is NPT the same as Flare?

No, NPT and flare fittings are not the same. NPT fittings have tapered threads and seal through thread compression.
Flare fittings, on the other hand, have a flared end that is compressed by a flare nut against a mating surface to create a seal. Their designs, sizes, materials, and applications are different.
NPT is more commonly used in high – pressure and industrial applications, while flare fittings are often used in low – to – medium – pressure applications like automotive fuel lines.

What is the advantage of flare fittings?

Flare fittings provide a secure, leak-proof connection that can handle high pressures and temperatures. They are also reusable and durable.

What is the difference between JIC and NPT threads?

JIC threads have a 37° flare seat, while NPT threads are tapered. JIC fittings are commonly used in high-pressure hydraulic systems, whereas NPT is used in plumbing.

Are flare fittings reliable?

Yes, flare fittings are highly reliable for high-pressure and high-temperature applications. They ensure a secure seal without additional sealants.

How do I convert NPT to flare fitting?

Use an adapter, such as a 3/8 flare x 3/8 NPT adapter fitting, to connect NPT threads to flare fittings. Ensure proper sealing and compatibility for your application.

Where to buy fittings?

Contact Dingfeng for custom fittings. We offer a full range of products, including NPT and flare fittings. Reach out anytime!

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