If you enjoy DIY plumbing, you’ll no doubt run into the need to use compression fittings on your copper pipes. When will that be?
You’ll want to use compression fittings in a situation where the run of pipe needs to be taken apart or when an area of the pipe will be difficult to solder. One common location in which this occurs is on supply lines to a bathroom, laundry, or kitchen sink because they have compression fittings at both the stop valve and the faucet inlet.
Table of Contents
- Here’s What You’ll Need
- How Does a Compression Fitting Work?
- How to Make a Compression Joint
- How to Join a Compression Union
- Frequently Asked Questions
- Final Thoughts on Compression Fittings
- Call 1-Tom-Plumber
Here’s What You’ll Need
You won’t need much to complete this simple compression fitting project.
About 15 minutes to make a simple connection.
Here’s the part you’re really going to love. You need no particular skills for this project.
Two crescent wrenches and some pipe joint compound.
How Does a Compression Fitting Work?
Okay, time to get into the nitty gritty of compression fittings. But first, we need to explain how a compression fitting works. While reading this, take a look at the diagram below. It will help you visualize how everything’s put together.
The compression nut forms a seal by squeezing the ferrule against the copper pipe. A ferrule is a metal band that forms or strengthens a joint.
Because copper is a soft metal, the seal can be extremely tight. Use pipe joint compound (or Teflon plumber’s tape) to make sure the seal is watertight. You should also anchor or support the tubing within two feet of either side of the fitting.
How to Make a Compression Joint
Here are the four basic steps in making a compression fitting joint.
1. Shut Off the Water
As always, when working on a plumbing project related to your water pipes and compression fittings, start by turning off the water shut-off valve.
2. Position the Parts
Bend the tubing into position and slip on the nut and the ferrule. The ferrule (a metal band used to strengthen a joint) will not go on if the tubing end is bent or less than perfectly round. You may have to sand it with emery cloth to get it to slide on. Smear pipe joint compound (like Pro Dope) on the ferrule and the male threads of the fitting.
3. If the Tubing Kinks
If you don’t bend the pipe in a gradual, sweeping arc, you’ll be surprised how fast it will kink. And a kink in the pipe is nearly impossible to get back to the right shape. You’ll need to throw the piece away.
A good way to do this safely is to use a coil-spring tubing bender, a device that is inexpensive and will allow you to bend either soft copper or aluminum.
4. Tighten the Nut
Tighten the compression nut with a wrench, forcing the ferrule down into the tubing to secure and seal the connection. If the joint leaks when the water is turned on, tighten the nut a quarter turn at a time until the leak stops. Don’t over-tighten the joint. Too much pressure can crush the tubing or crack the nut.
How to Join a Compression Union
If you don’t need to create a compression joint, but rather need to join a compression union, then follow these steps.
1. Shut Off the Water
I know, it gets annoying having to read this same instruction over and over. But really, it’s that important. Too many water damage disasters have happened because this simple step wasn’t followed. We’ll spare you by not showing you the picture again.
2. Position the Parts and Join Them
Bend the pieces into position and slip a nut and a ferrule onto each piece of tubing. Smear pipe joint compound on the ferrules and on the male threads of the union. Slide the pieces together and hand-tighten the nuts until they are snug.
3. Tighten Each Side
Place one crescent wrench on the union. Use your second crescent wrench to tighten each side (the first wrench is used to keep the pipe stable while you’re tightening with the second wrench).
Once snug, tighten about one more half turn. Turn the water back on, and if there’s a leak, gently tighten a bit more.
Frequently Asked Questions
Compression fittings are more reliable than threaded fittings. They are easier and faster to install than soldering. And they are safer because no torch is needed. However, compression fittings can be prone to issues from vibration and repeated bending.
In a DYI situation, the most common cause is over-tightening. Follow the instructions above for how far you can tighten.
Probably not; you’ll need to cut it off.
Final Thoughts on Compression Fittings
Compression fittings are a great solution for do-it-yourselfers who want a safe way to join (or connect) their copper pipes without a torch. Although not without their potential issues, they are commonly used to make watertight connections quickly and easily.
We can help you repair, remove, or install any type of pipes and fittings, including compression fittings and other solutions. We will also immediately respond to any of your emergency plumbing, drain cleaning and drain clearing, or water damage problems. And we have specialists who excavate, repair, and replace broken sewer lines.