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Flare Fitting Vs Compression Fitting – A Detailed Comparison!

Fitting work requires extreme care to ensure leak-tight seals eliminate any leakage risk. One can use several types of fittings to ensure plant or plumbing safety and operational efficiency. Therefore, let’s compare the two common types of fittings.

So, how do flare fitting vs compression fitting compare? Flare fitting is used in piping highly flammable gas and high-pressure liner that would be fatal in case of leaks. On the other hand, compression fittings are used for water piping and compressed air lines that would not cause any harm if they leak.

This guide compares both fittings used in plumbing and plant systems to transport fluids. In addition, we shall also review the applications of both types of fittings.

Flare Fitting Vs. Compression Fitting – A Detailed Comparison!

Fitting in the plant system or plumbing work aims to ensure a leak-tight seal of its content. Compression and flare fitting are the common methods used due to their reliability and affordability.

  • Flare fitting involves using a flaring tool to flare the edge of the tubes to be later connected using a flare union with threads. The flare union key has an outward protruding 45-degree corn that fits into the flare. It’s created by the 45-degree flaring tool on the tubes.

To secure the flare union, this method uses nuts on both ends, which are tightened to provide a leak-tight seal to the connection.

  • On the other hand, compression fitting uses a compression nut to hold two pipes together. The fitting consists of three parts, namely:
  • A tapered nut with internal threads
  • A brass ring known as a ferrule or olive
  • A tapered insert fitting

The tapered nut is tightened to press the ferrule between the tubing and the tapered insert fitting on both ends, forming a secure leak-tight joint.

How To Do A Flare Fitting?

Flare fitting provides a leak-tight seal of dangerous and flammable gasses that would cause havoc in case they leak. Therefore, having a flawless connection is essential if you plan on doing it yourself.

However, flare fitting should only be done on the following materials; aluminum, copper, brass, and welded or soft steel, as they can form a reliable flare.

Have the following tools and equipment.

  • 45 degrees SAE-style flaring tool
  • Tube cutter
  • Reamer
  • Thread oil
  • Two adjustable wrenches

For ease of connection, follow the process here step-by-step.

Step 1: Cut the tube square and ensure the edges are free from any damage, including dents or gouges that may prevent proper connection using a reamer

Step 2: Slide the nut onto the tube with the threaded end facing outward

Step 3: Flare the tubing end with a 45-degree flare tool

Step 4: Inspect the flare for splits and thread the flare nut onto the fitting

Step 5: Repeat the procedure for the other tube ending to be joined together

Step 6: Slide the nut to sit on the flare outer side and screw in one end of the flare union

Step 7: Use one wrench to stabilize the flare union and the other to tighten the nut

Step 8: Tighten until it feels properly tightened, and then tighten a quarter turn more. You can apply thread oil for ease of tightening

Step 9: Attach the other tubing to the other end of the flare union with the flare sitting well on the flare union and tighten it properly

Step 10: Test the fitting for any leakage

flare connection components

Figure 1: Flare Connection Components.

Click on the link below to watch this video on flare fitting to connect copper pipes.

How To Do A Compression Fitting?

A compression fitting is common in most domestic and commercial plumbing works where a quick fix is required with less risk in case of leakage. This type of fitting works with brass, plastic, soft copper, and stainless steel.

When selecting the ferrule or olive to use, measure the outer diameter of the tube to be connected and transfer it to the internal diameter of the ferrule. For example, if your copper tube has an external diameter of 5 inches, use a ferrule with an equivalent internal diameter.

For ease of connection, assemble the following tools and equipment.

  • Two adjustable wrenches
  • A compression fitting with nuts and ferrules
  • PTFE
  • Tube cutter

Follow the steps below to do a compression fitting on copper tubing.

Step 1: Make grime less cut on both ends of the tubes to be connected

Step 2: Slide the tightening nut into the tube with the thread end facing the joint

Step 3: Slide the ferrule to follow the tightening nut

Step 4: Repeat the procedure for the other tube endings

Step 5: Insert the ends of the tube into the tapered insert fitting

Step 6: Slide up the ferrules till they fit between the tube and the tapered fitting

Step 7: Push the tightening nut from both ends and tighten them using your hand. You can then apply force using the adjustable wrench, with one holding the tampered fitting and the other tightening the nut.

In case of a repair, wrap the ferrules with PTFE tape to ensure a leak-tight seal.

compression fitting components

Figure 2: Compression Fitting Components

Click on the link below to watch this video on how to do a compression fitting.


Here are frequently asked questions on compression and flare fitting.

Q: What Should I Do If I Find A Compression Or Flare Fitting Leaking?

First, tighten the fitting nuts using a wrench or adjustable pipe tools on both ends. If the leakage persists, close the main gate valve to stop the flow of content and disassemble the fitting for further diagnosis.

If the fitting is faulty, seal it with new fitting components. You can consult a professional plumber if it looks complicated for you.

Q: Which Is Better, Between Flare Fitting And Compression Fitting?

To answer this question, you need to focus on the intended use of the fitting method. Use the flare fittings if you plan to connect tubing for gas and high-pressure lines.

On the other hand, if you wish to do a water or compressed air connection, apply the compression fitting. However, you can use the flare fitting for plumbing as it offers a strong leak-tight seal.

Q: To What Extent Should You Tighten A Compression Fitting?

A compression fitting should be tightened to ensure a leak-tight seal without damaging the threads or the pipe warping. Tighten with less than a ¾ turn, then test if the fitting needs further tightening.


Flare and compression fitting connect two or more pieces of tubing that may be hard to join with other methods, such as sweating. When comparing flare fitting vs compression fitting, both are essential in plumbing work but flare fitting offers a more reliable and leak-tight seal than compression fitting.

Follow the given processes carefully step-by-step to join two pieces of pipe. However, you can consult a professional plumber to fix the connection if you find it difficult to fix.