Compression Fittings: Everything Plumbers Need to Know

Compression Fittings (Blog Cover)

As a plumber, you are going to need to make compression fittings your best friend. Some veteran plumbers liken compression fittings to Snap-On ties: they are quick, easy and sort of your go-to when all else fails. 

But to look at compression fittings as last resort tools would be doing yourself a disservice and belying the true value of these pieces of equipment. The basic principle behind compression fittings is that they are used to join two pieces of thin-walled tubing, pipe, and in some cases a pipe to some sort of valve or fixture. 

You can see compression fitting in other industries as well. Electricians often use them in their line of work and they are even used for hazardous waste materials. The reason they are used in such high-risk types of jobs is that they are extremely reliable and form a water-proof seal in pipe assembly. That is when they are chosen and installed correctly. 

Compression fittings are something you will have to know inside and out as a plumber. So if you are an apprentice or just starting out on your journey as a plumber or contractor, today’s post will be of particular interest to you. Today is all about compression fittings: what they are, how to use them, and what they are used for. Consider this your primer guide to these indispensable plumbing tools. 

If you would like even more resources for your plumbing business or for yourself as a tradesman, please don’t hesitate to call us and find out how to become a member of the Plumbing, Heating & Air Alliance.

The Basic Components of a Compression Fitting

There are 3 basic components to any type of compression fitting: the compression nut, the ferrule (sometimes called the compression ring) and the compression fitting body) sometimes referred to as the compression seat). Here are the functions of each of these components:

  • Compression Nut – The compression nut looks like your basic nut – usually hexagonal. And it functions exactly like a nut. The Compression nut tamps down on the compression ring as it is tightened with a wrench.
  • The Compression Ring – The compression ring is sort of the go-between of the entire operation. It works between the nut and the compression seating and gets pressed into the seating as the nut is tightened.
  • The Compression Seat – The compression seat receives the tube that is to be connected as the compression ring is inserted under it. The seat keeps the ring in place and makes sure that it is being pressed into the tubing, forming a watertight seal…ideally.

Compression Fitting Uses

One of the most important things to remember about compression fittings is that they should only be used on stationary connections. Fitting a pipe to a valve for example would be the ideal time to use a compression fitting because in this scenario, neither the valve or the pipe being fed into it are likely to move. Rather, the fitting is there to form a watertight seal. In general, here are the steps for using a compression fitting properly:

  • Slide the nut onto the tube that is to be fitted
  • Slide the compression ring up onto the tube and into the nut with the threaded side out
  • Connect the tube or pipe that is to be fitted into the compression seat
  • Slide the nut and the compression ring down toward the fitting body
  • Screw the nut (and by proxy the ring) into the fitting body and tighten the connection with a wrench

Different types of compression fittings are available for different uses as well. For example, the lines that supply refrigerators with water to be filtered will typically be sealed with quick-connect compression fittings. Another common application that calls for the use of a compression fitting is any time you need to hook up a water line to pneumatic lines.

And here’s a tip for all you newbie plumbers out there straight from the mouths of our plumbing community members: it’s always a good idea to lubricate the nut thread before using it to join any kind of pipes or tubing. In rare instances, you will be able to reuse old compression fittings. In such cases, you will definitely want to lubricate the threading. But it is just good practice to get into the habit and even lubricate new fittings. 

Other Compression Fitting Tips

So at this point, we’ve done a pretty good job of scratching the service. And surely, there is no better teacher than hands-on experience. As you go out into the field and use compression fittings in your work, you will learn much more about how best to use them.  All the same, here are some helpful tips to keep in mind when working with compression fittings:

  • Don’t Overtighten – Tighter is not always better – especially with certain kinds of tubing. Rigid pipes can stand a lot of torque, but thin piping like copper or thin-walled tubing can’t. Do not overtighten plastic tubing. This will cause a puncture in most cases.
  • Reusing Fittings – It is a good practice to use new compression fittings as much as possible – especially if they have been used on rigid piping. The threading of the ferrule (or ring) can get worn down over time and become unreliable. 
  • Plastic Compression Rings – When dealing with plastic tubing, always use a plastic ferrule (or compression ring). Use a plastic ring instead as a metal ring can damage the tubing.

Get Help from the Pros

Here at Plumbing, Heating & Air Alliance, we specialize in putting consumers and professionals in touch with the contractors that can help them. As a new plumber, you will need the guidance and resources that we can offer. Not just for knowing how to use tools like compression fittings, but to grow your business and operate efficiently. That is what we are all about at Plumbing, Heating & Air Alliance so talk to us and find out how to become a member.