Can You Connect PEX Pipe To Copper?

PEX pipe is a popular alternative to traditional piping materials, like PVC or galvanized steel. Copper is another common choice, despite its steeper pricing. Both materials are excellent choices for their own reasons, but can you use them together? Will there be any adverse side effects?

If you’re questioning the compatibility of PEX and copper, you’re in the right place. We’re here to tackle this topic, so continue reading to learn more!

What Is PEX?

Before we get started, let’s discuss PEX pipe. Since not everyone is familiar with the term, it stands for cross-linked polyethylene (PEX) pipes. PEX piping comes in long red, blue, and white rolls. The material is flexible, which is excellent for climates where frozen and burst plumbing is a common issue. 

In addition, the flexibility lends well to installation. Instead of using an excessive number of joints and fittings to make the pipe fit, it bends easily enough to turn corners. The benefits of PEX are extensive, making it a popular choice in underground and covered plumbing scenarios. 

Since the molecular composition of PEX disintegrates in sunlight, it can only be used underground or in areas where it doesn’t get direct UV exposure.

Other Common Types Of Pipe

There are a few different types of pipe used for plumbing, each with its own set of pros and cons. The plumbing pipes in your home serve a critical role, so choosing a durable, long-lasting option is essential. 

A few of the most common types of plumbing pipe include:

• PVC: Polyvinyl chloride (PVC) pipes are commonly used for the plumbing of sinks, toilets, and shower drain lines. The plastic tubing is a popular choice, as it resists rust and corrosion better than other types of pipe. They’re surprisingly durable and will last indefinitely unless subjected to damage.
• ABS: Acrylonitrile butadiene styrene (ABS) pipe is relatively similar to PVC in nature. However, the two are easy to differentiate due to the color difference. ABS is often used for vent and rain lines and is resilient to cold temperatures. 
• Copper: This material has been a staple in plumbing for many years. It can last for up to 50 years and is commonly used in sinks, showers, tubs, and several other fixtures in new and old homes. These pipes are corrosion resistant, can handle high water pressure, and are tolerant of both temperature extremes.
• Cast Iron and Galvanized Steel: These pipes aren’t common in new builds but were standard in homes built in the early 20th century. Cast iron is durable but prone to rust and corrosion, making it a poor choice for water lines, as it can contaminate the water supply. These pipes were often used for sewage and other drainage purposes. 

Can PEX And Copper Be Used Together?

Yes, PEX and copper piping can be used together. They are compatible, and there aren’t any concerns regarding adverse effects between the materials in either’s composition. So, if you already have existing copper plumbing but need to add to or manipulate the existing pipeline, consider using PEX.

What Is The Best Way To Connect PEX To Copper?

There are a few different ways to connect PEX to copper plumbing. Really, the best method depends on what you’re familiar with and comfortable with. Since everyone’s preferences are different, here are a few different ways to connect PEX to copper.

Depending on the particular method you choose, you may need special tools for your project. 

Use Push Fittings

For copper-to-PEX connections, you can use push fittings (push-fit connectors). These fittings are incredibly easy to use and are simple to connect. You won’t need any additional tools, clamping, or crimping to join the two pipes together.

These fittings are available under the brand name Shark Bite and are composed of brass. You need to be careful with the materials you use for the fitting, as some metals will corrode copper. However, brass coexists well with copper, so it isn’t an issue. 

The fittings come with internal tines that hold the pipes tightly against an internal O-ring, which creates the necessary watertight seal. The name indicates how these work: simply push the fitting onto the pipes to install them. 

For the fittings to work as they should, the pipes must be fully inserted. Measure the insertion depth on each pipe, then mark a line. This way, you’ll know for sure that the pipe is fully inserted when the line is flush with the edge of the fitting. 

Before you insert the PEX pipe into the fitting, you’ll need to insert a support sleeve. Since the tubing is flexible, the plastic sleeve helps prevent the walls from collapsing, which would compromise the seal.

To do so, place the sleeve all the way into the pipe, then insert the pipe all the way into the brass fitting. On the other side of the fitting, ensure the copper pipe is free of oxidation. Copper is plenty sturdy on its own and doesn’t need a support sleeve, but make sure the pipe is free of oxidation. 

Use Threaded Connectors

If you prefer not to use brass fittings, you could also use threaded connectors. Threaded adapters are available with male and female threads and work well to connect PEX and copper. 

Screw the adapter onto the copper end, then use plumbing tape and a wrench to create a leak-proof, watertight connection. On the other end, push the PEX pipe into the barbed connector. Secure the PEX pipe with a crimp ring. 

Use Solder-On Connections

Solder-on connections are another option for joining the two materials. Like the fittings, these connections are also made of brass. They’re available in two different varieties: female sweat adapters come with a slip connection that fits over a pipe, and male sweat adapters slip inside a fitting. 

For example, you’d use the male fitting option if you want to connect PEX tubing directly to an existing tee or elbow. You’ll find a barbed tube that fits within the PEX pipe on the other end of these solder-on connectors. 

To use solder-on connections, solder the fitting onto the pipe. Then, push the PEX tubing on the connector and allow the metal to cool. After the metal cools, push the PEX pipe onto the barbed connector until it’s fully seated. 

Lastly, use a crimping tool to secure the connection. Crimp a clamp around the PEX pipe using the crimping tool. 

Other Fitting Options

Various threaded fittings are available to connect PEX and copper pipes. A few of these options include:

• Expansion fittings: These fittings insert into the PEX pipe with a bit of assistance. Using a PEX expander tool, stretch the diameter of the pipe to accommodate the fitting. Then, the PEX tubing will return to its original size, creating a leak-proof seal.
• Compression fittings: With these fittings, you need a few different parts, which are all available separately. A brass nut fits over a plastic compression ring over the PEX pipe with a metal sleeve inside the pipe for support. Once the fitting is inserted into the PEX pipe and sleeve, tighten the nut to the fitting. This squeezes the compression ring, forming a watertight seal.