Polyethylene, or PEX for short, is a crosslinked matrix used as a plumbing material that’s recently become increasingly popular.

The new building codes include PEX as a requirement for use in both old and new constructions.

PEX is a flexible tubular plumbing system that works based on compression and involves plastic or metal insert fittings and other mechanical methods.

On the other hand, CPVC is a hard plastic piping system that involves jointed joints which you can glue together.

In this article, I’ll talk about bonding PEX to CPVC, so stick around for more information!

Also, check out my guide on CPVC vs. PVC glue for more tips.

Is It Difficult to Bond PEX to CPVC?

CPVC isn’t the same as PVC. While it may have been easy to bond PEX to PVC, it’s not the same for CPVC.

CPVC is chlorinated as an extra step and can endure higher heat levels than PVC.

PVC is less expensive and doesn’t rust, so many professionals use PVC for drain lines. But CPVC has its uses, especially in the creation of PEX.

CPVC doesn’t have any compression fittings, so it’s difficult to bond them to PEX. A PEX adaptor must be used to form the pipe thread connection.

What Is CPVC?

CPVC stands for chlorinated polyvinyl chloride and is very resilient and durable.

It’s a thermoplastic material often used for cold and hot water applications in various residential constructions.

CPVC is highly resistant to damage from chlorinated water and is much more heat-tolerant than PVC.

If you didn’t know, water companies use chlorine-based disinfection solutions to destroy bacteria in the water.

However, PVC pipes are weak against chlorine-infused water. CPVC pipes aren’t!

What Is PEX?

PEX pipes are made from medium or high-density polyethylene because they’re sturdy and flexible at the same time.

PEX piping systems have long been used for hot and cold-water distribution systems, and hydronic radiant heating.

PEX pipes are very easy to work with because they’re compatible with most plumbing codes.

Moreover, they’re great for remodeling because you can easily place them on the walls, thanks to their flexibility.

Are CPVC And PEX Compatible?

When talking about PEX plumbing, I need to refer to the connections that need a specialized tool that seals the tubing of the fittings.

In other cases, a nut and compression ring is necessary to seal the fitting.

CPVC pipe fittings, on the other hand, are secured to the pipe with solvent-based adhesives that essentially fuse the pipe to the fittings.

However, applying heat to PEX tubing will soften, and the connection won’t be stable.

PEX tubing is made from flexible plastic, so it’s not compatible with CPVC fittings.

The rigid plastic in the fittings can’t be set into place for a crimping system. It won’t spread enough to allow a compression fitting.

However, push fittings are universal and work with CPVC and PEX piping. These fittings use an O-ring to keep the pipes stable against the internal gasket.

It’s just like a quick-release fitting on an air hose.

You should push the PEX tubing to one side of the fitting and the CPVC tubing to the other.

Now you’ve connected PEX and CPVC without using special tools or adhesives.

Are CPVC and PEX Similar in Size?

While CPVC and PEX are nearly identical in most respects, their material composition is different.

CPVC pipes go into a special fitting similar to copper, while PEX pipes have internal diameter reductions for every fitting.

Is PEX Plumbing Bad?

We’ve been using PEX plumbing for a very long time, so we’ve had time to notice its failures.

A major problem with PEX plumbing is the piping and fitting systems.

More specifically, if the piping and fittings come into contact with chlorinated water, they’ll slowly dissolve and loosen.

How Do You Connect PEX And CPVC?

Push fitting has become more and more popular in plumbing. You can find several brands of push fittings at your local home improvement store.

While these pieces are a bit expensive, it’s a cheaper alternative than going from failure to failure with other fittings.

Think if you had to reposition the entire plumbing lines to another system because of compatibility issues.

It would have cost much more than simply buying push fittings. These fittings can be reused, so you won’t need to buy new ones when you make a mistake.

Before connecting the PEX and CPVC systems, ensure no debris in the pipes.

Then, look for any visible cracks, burrs, nicks, or other types of damage. If possible, remove them with a razor blade on the PEX piping and sandpaper on the CPVC piping.

To make a good seal, the pipe that goes into the fitting needs a smooth end. After that, press the push fitting onto the CPVC pipe until it can’t go any further.

After you’ve fitted the rigid CPVC pipe, press the other side of the push fitting on the PEX tubing. Now turn on the water and see if the tubing leaks.

To connect two PEX piping systems, you should use “SeaTech” and “Sharkbite” fittings. You can’t, under any circumstance, seal, weld, or attach PEX piping pieces directly to one another.

Follow the steps below to connect PEX to PEX:

• Remove any excess PEX tubing from the flashing
• Slide the PEX crimp ring over the tube at about 2 inches past the end
• Push the PEX fitting into the PEX tubing all the way
• Position the PEX crimp ring at about 1/4’’ – 1/8’’ from the end of the tubing
• Open the jaws using the PEX crimp tool

If there are leaks in the tubing after you’ve connected the two pipes, you have to repair the leak. To do this, follow the steps below:

• Remove any damaged section of the PEX tube with the PEX tubing cutter
• Prepare a new piece of PEX tubing that’s longer than you need to make the repair
• Connect the tubing to the fitting using the Crimp Connection Method and then check the connections with the Go-No-Go gauge

That’s about it. Now you’ve connected PEX to PEX tubing and repaired the leaks. Repeat the process should you encounter more leaks.

But if you do it right, it shouldn’t leak anymore.

Wrap Up

Remember that most PEX plumbing line fittings need a special tool to crimp the tubing on the fitting.

As for CPVC pipe connections, you’ll need solvent-based glue to seal everything into place. If you have more questions, leave them below, and I’ll answer quickly!