What Is Compression Fitting And How Does It Work? – Basic Explanation

A compression fitting is indispensable in every plumbing install or repair process. Still, only plumbers or people who prefer DIY plumbing know about this phrase.

If this is the first time you install a DIY plumbing system or fix a plumbing connection of your bathroom, dishwasher, etc, learning about compression fitting is inevitable! Even though it is not an easy task, don’t be discouraged!

Scroll down to get the answer to the question “what is Compression fitting and how does it work?” and helpful instructions in this article!

What Is Compression Fitting And How Does It Work? 

A compression fitting is often known as an excellent attachment that can withstand high pressures and provide a reliable, tight seal. As a result, it is usually utilized in DIY plumbing systems installation processes.

What Is Compression Fitting? 

It is a type of fitting used to connect water pipes and electrical conduits and can be used to join tubes or thin-walled pipes together. Besides, you can attach two different pipes with the help of a special compression fitting.

What is a compression fitting
A compression fitting.

You can utilize it anywhere you need a connection, whether between water lines or compressed airlines. It can be installed everywhere in your home, under the sink, under the dishwasher, etc. However, even though there is a connection between the pipes, sometimes no compression fitting is needed, such as a drinking water pipe system. You will need a quick-connect fitting or a quick disconnect instead.

The most special thing about this fitting is that no heat is needed, so it is incredibly safe and easy to use. Moreover, the fitting is also extremely popular among people who like DIY plumbing systems.

It has various designs and plenty of different manufacturers, but they all have the same standard: extreme temperature and pressure resistance ability and aggressive fluid compatibility. 

Furthermore, most compression fitting has these three elements: a compression nut or screw, one or more ferrules, and a compression fitting body.

basic elements of Compression Fitting
Three basic elements: The nut, the sleeve, and the fitting.

How Does It Work?

Basically, a compression fitting presses a fitting component to another one and creates a watertight seal. You can test it in your house to understand more clearly. It may be underneath your sink, where compression fitting is essential to connect the waterline.

Compression fittings work by compressing “Olives” between the fitting, nut, and pipe faces. Plumbers often use wrenches to clamp the nut to the pipe. Thanks to that, pressure will be created.

In addition, metal compression fittings are generally easier to disinfect and clean than other materials. That’s why it also has high purity applications. You can easily see these applications in the medical, semiconductor, and instrumentation industries. They often use metal compression fitting to join the air hoses together, which can help prevent contaminants from escaping from the air tube.

This type of fitting is also a perfect choice for high-pressure applications. Large compression fittings can be used in pressurized environments of up to 10,000 PSG. Therefore, the high-pressure bottling, hydrogen fuel cell, and aerospace industries frequently use compression fittings.

How compression fittings work – Plumbing Tips

How To Select Compression Fitting?

The most important application of compression fitting is to compress the flow of water or air. Therefore, you need to choose a compression fitting that is strong enough to allow only the necessary amount of water to pass through without undue pressure drop. Here are a few important factors you might want to look out for before purchasing a compression fitting:

The first factor you must pay attention to is the pressure and temperature of the location you want to install your fitting. Inappropriate pressure can lead to limiting the working ability of pipes and fittings, even damaging them. Remember that most fittings cannot be used in an extreme environment. Small tip: You should look up this information online carefully before starting to install it.

Nevertheless, considering the compatibility of materials is also essential. Unsuitable fluids can lead to rapid corrosion. With highly corrosive liquids, you can use PTFE fixtures to minimize the corrosion rate.

Pay attention to pipes and fittings dimensions before buying! There are many types of different sizes. Thus, to install them easily and without extra effort, you should buy fittings with the right index for the channels you want to install.

Compression fitting

How To Install A Compression Fitting On Plumbing Pipes? 

It shouldn’t be that difficult to install a compression fitting into your DIY plumbing. In fact, there are only three simple steps to follow. Here is a step-by-step guide to doing the installation. Read to learn more!

1. Preparation And Cleaning

First, prepare what is necessary for the installation. You only need two wrenches and a pipe dope without complicated preparation. Do not forget to choose wrenches that are the right size for your pipes and fittings!

The pipe cleaning is essential in ensuring smooth installation progress. Use a damp cloth or paper towel to wipe the outside of the tube. If using those types of cloth is not enough, you can also use an emery cloth to clean the pipe. The abrasive papers help clean the pipe and make the pipe no longer rough, easier to install.

If there was a kink in your pipe, you might want to cut it off. Leaving that kink alone may cause joint leakage.

Be aware of any signs of the fitting.

2 Place The Fitting

Now, when the pipe is ready, it’s time to place the fitting on it! Slide the retainer nut in, and be mindful of aligning the distance to have enough room for the next equipment. To make it easier to put in, you can lubricate the nut beforehand, not over-lubricating to avoid causing looseness.

After finishing the nut placing process, you should put the sleeve in and final the fitting. Keep in mind to ensure proper penetration to avoid the possibility of leakage. Besides, it would help if you used prepared pipe dope for leak prevention and pressure sealing during the installation process. Just a small amount is enough to make everything stable!

3. Tighten It! 

This is the last and most important step. If the joints do not match, water can leak, causing waste and reduced compressibility.

Slide the nut and the ring closer to the fitting. Then, tighten it! You can use a wrench or manually install the nut onto the fitting, as long as it’s tight enough not to fall out.

Next, use two prepared wrenches to tighten nuts and joints. You should put one on the fitting and the other on the nut. Tighten it one more time after you put the wrenches in their correct places. More specifically, this will cause the sleeve to create a seal between the fitting and the pipe.

The creaking of the internals indicates the success of the screwing process. If you hear this sound while you are twisting, it means that the internal components have started to create friction!

Tighten the nut and finish the installation process.
Tighten the nut (2) and finish the installation process.

There is a simple tip to let you know if the coupling is in place. Screw the nut a little tight, then hit the back of the coupling. If it bounces back, you’ve misplaced it.

What To Do If Compression Fitting Is Leaking? 

Water leakage is not an uncommon case, but it is quite easy to solve. Yet, you might need to spend time finding out the reason and try different solutions!

If the fitting causes a leak, turn off the water to find out where it is coming from. Normally, a new compression fitting won’t cause water leakage, especially if you’ve installed it correctly. 

The cause of leaks in new DIY plumb systems often comes from improper installation or inaccurate fitting. Buy a new fitting or try to tighten the nuts again!

In case your plumbing system is old, it may leak due to deterioration of the fitting. Then, it would be best if you tried to repair it by loosening the nuts. This will help break up the resistance caused by corrosion of the environment and time, giving more space to turn the nut. 

Be aware to re-tighten the nut immediately afterward. If you forget, loosening will have no effect!

Old compression fitting
Old compression fitting.

Inappropriate materials may also cause this headache problem. The plastic compression fitting might not be a good option, as it will break down quickly in excess vibration areas.


Above is all basic and in-depth information about compression fitting! After reading this article, we hope that you can now answer the question, “what is compression fitting, and how does it work?” As long as you follow our guides and tips in this article, we believe your DIY plumbing installation process will become much more simple. Still, please note some important things we mentioned in the leaking issue part for a timely solution!

Hope we helped you and provided you with some interesting knowledge! Good luck with your DIY plumbing!

Leave a Comment