How To Install A Compression Fitting On Plastic Tubing? Just 5 Steps

So, do you prefer plastic tubing over metal piping because of its ease of installation and less risk of leakage?

Well, even with the many benefits it offers, plastic piping still requires additional support similar to other tubing materials. And this is where a compression fitting comes in.

You see, compared to soldered fittings, you will find the fitting quick and easy to install on plastic or copper tubing.

Even so, not everyone can install the fitting correctly. This is true, especially if you don’t know how compression fitting works with plastic.

Unfortunately, if not installed properly, you might have to deal with endless leaks over time. Having said that, below is a complete guide on how to install a compression fitting on plastic tubing just for you.

How Does A Compression Fitting Work With Plastic?

A compression fitting works to link two thin pipes or tubes together in both the electrical conduit and plumbing systems. But how does the fitting work with plastic?

Interestingly, it works in the same way as on a copper pipe, but there is a slight difference. Simply, with plastic piping, you have to use an insert or liner.

Now, this is how a compression fitting works with copper. You first fit a compression nut into the copper. This works to compress the compression O-ring between the fitting.

Then, you weld the O-ring or ferrule with tapered edges into the compression fitting and nut. Consequently, you will end up with a watertight seal between the pipes.

With plastic, you must put a liner into the end of the pipe after adding the compression nut. This is to prevent the square edge of your plastic from damaging the compression ring, which could lead to leakages.

How To Install A Compression Fitting On Plastic Tubing? 6 Easy Steps

Plastic tubing offers many benefits compared to alternative piping materials, such as ease of installation and resistance to chemicals.

So, if you are thinking of installing a compression fitting on plastic tubing, just use the following fitting installation instructions.

Step 1: Gather your installation tools

Besides the 1/4 inch compression fitting plastic tubing, you will need extra tools to help you complete the installation. These include:

• PVC and CPVC tubing cutter or hacksaw
• Adjustable wrenches
• File
• CPVC or PVC pipe
• Brass insert

Step 2: Trim your plastic tubing

Get your PVC pipe and cut the tubing to your preferred size. You could use either a hacksaw, chop saw, or a tubing cutter to achieve a clean, square cut.

After cutting your pipe, you might end up with rough edges. Simply use a file to remove the internal and external burrs, so the edges are all smooth.

Step 3: Take apart the compression fitting

Most brass compression fittings come already assembled. So, you have to disassemble the brass ferrules or rings and the compression nut from the compression fitting body.

Step 4: Position the parts of the compression fitting

Start by slipping your compression nut over your pipe. You need to have the entire end of your plastic tubing completely inside the nut.

After that, slide your fitting’s ring or ferrule onto your PVC pipe. You will notice that the ring has a taper. So, the fat end of the taper should face the compression nut while the small taper should go towards the fitting body.

Step 5: Fit the brass insert

Next up, you need to insert the brass insert inside your plastic tubing for additional support. Make sure to push it inside until you feel it cannot slide anymore.

Step 6: Tighten the fitting

After that, get your adjustable wrench and tighten the nut once more. You may use another wrench to securely hold the compression body.

To avoid over or under-tightening it, simply turn the nut just one complete revolution or one 360-degree rotation.

How Do You Seal Compression Fittings?

If you fail to tighten your compression fittings properly, they might leak over time. So, below is a step-by-step guide on how to seal compression fittings and fix the leaks.

Step 1: Retighten the fitting

Before anything else, first shut down the water supply to your fitting. Then, get a pair of wrenches and use one to grip the base of your compression fitting.

Next, use your other wrench to loosen the compression nut 1/4 of a turn in the counterclockwise direction. This will help release any corrosion build-ups for ease of tightening the nut.

After that, turn the nut 1/2 of a turn in the clockwise direction to tighten it. Then, wipe the fitting dry before turning on your water supply. Lastly, look out for any leaks.

Step 2: Install a new ferrule or ring

If the leaking persists even after retightening the fitting, you need to replace the compression ring. Following fittings installation instructions, first, turn off the water supply. Then, unscrew the compression nut from the fitting using your wrench.

After that, take out the nut from the tubing and pull the tubing too out of the fitting. Next up, cut the tubing using a pipe cutter and remove the old ferrule. Then, fit in your new ferrule over your tubing.

Step 3: Use pipe joint compound

To completely seal your copper or brass compression fittings, you could use a pipe jointing compound or PTFE tape. Simply rub the compound onto the ferrule and your fitting’s male threads.

Then, slide your tubing into the compression body, tighten the nut with your hand, and lastly, use a wrench. Your fittings should be completely sealed at this stage.

How Tight Should Plastic Plumbing Fittings Be?

You must not overtighten your fittings. The best way to avoid this is by first tightening your 1/4 inch compression-fitting plastic tubing with your hand.

Simply tighten it until you cannot do it anymore. After that, get your wrench and make just one or two full turns. Now, even if you get tempted to make another turn, you should not dare.

Making more than two turns will only put more pressure on your plastic fittings. Once this happens, your fittings might develop a crack or start leaking.

You may also like – 7 Best PEX Crimp Rings in 2023 – Reviews & Buyer’s Guide

Conclusion

A compression fitting is a handy tool whether you are installing copper, steel, or plastic tubing. This is because it offers maximum support for your piping.

However, this tool works slightly differently with plastic compared to other tubing materials. The difference being you have to use an insert during installation.

Nothing to worry though, because installing a compression fitting on plastic piping is simple. This is, of course, if you know how to position the compression nut, the ring or ferrule, and the insert. And most importantly, how to correctly tighten the nut to avoid leaks.

But besides knowing how to install a compression fitting on plastic tubing, you must learn how to seal the fittings too.

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