April 30, 2025
PEX Cold Expansion vs. Copper Press: Choosing the Right Fitting Solution
By Alex Gross
One of the most important parts of any construction project, residential or commercial, is choosing a reliable, high-performance plumbing system. Equally important; choosing an appropriate fitting solution. The right fitting can ensure performance and reliability throughout the life of the plumbing system, offer unparalleled safety and efficiency, and promote profitability during the project and after it is completed. Choosing unreliable fitting solutions can result in costly failures that jeopardize your reputation as well as the safety and integrity of your project.
How PEX Cold Expansion Works
Cold expansion is designed for use with PEX-a pipe. There are three methods for manufacturing PEX — PEX-a, PEX-b, and PEX-c. PEX-a has the highest degree of crosslinking for the greatest flexibility, durability, and shape memory for cold expansion fittings. If you use cold expansion fittings with PEX-b or PEX-c pipe, you run the risk of microcracking the pipe, which can lead to leaks.
To make an expansion connection, you will need an expansion tool, fitting, and PEX ring. The connection is made when PEX naturally shrinks back to its original size and forms a secure connection around the fitting. This happens because the crosslinking in the pipe allows for the shape memory of the PEX material to shrink back to its original size.
Begin by ensuring the PEX pipe is cut squarely, perpendicular to its length, removing any burrs or debris from the cut end. Select the correct size ring for your pipe and slide it over the edge of the pipe. A stop edge on the end of the ring will ensure the correct 1/16" overhang over the pipe edge. Select the correct expansion head for your tool, insert the expansion head into the pipe and expand fully. Note that if using a manual hand expander tool, it is necessary to rotate the head after each expansion. Battery-powered expander tools will auto-rotate the head. Continue expanding until the pipe and ring reach the collar of the expander head. Immediately remove the expansion tool and insert the PEX fitting into the expanded pipe and ring. Ensure the pipe and PEX ring seat completely against the shoulder of the fitting. Then, let the pipe shrink back to its original size and form a secure connection around the fitting. The connection can be visually verified.
Advantages of PEX Cold Expansion
PEX cold expansion connections are quick to learn, help improve productivity and make connections faster and easier on the jobsite. Additionally, Uponor PEX-a is highly flexible, allowing for a tight bend radius and fewer required fittings for faster installations. Additionally, because PEX expansion connections do not require open flame or heat, they improve safety on projects and eliminate the need for fire-watch requirements. Plus, PEX is much lighter in weight than metallic piping options, which can help prevent jobsite injuries. Best of all, because PEX is not a traded commodity, it has lower, more stable material costs compared to copper.
Because of the shape memory of PEX-a, the pipe always wants to return to its original size. So, cold expansion connections continue to get stronger over time. Copper press connections, on the other hand, require more skill and cannot be visually verified. These connections rely on the tool to apply the correct pressure and the fitting and sealing element to perform as designed. If either component of the press tool is compromised, the reliability of the connection will be affected.
How Copper Press Works
To make a copper press connection, you need a press tool and press fitting. A connection is made when the force from the press tool joins the fitting to the pipe.
Begin by ensuring the pipe is cut squarely, perpendicular to its length, removing any burrs or debris from the cut end. Mark the insertion depth on the outside of the pipe to create a proper seal, then inspect the sealing element to ensure its correctly seated in the fitting groove and free of damage. Turn and slide the copper pipe until the edge of the pipe reaches the stop inside the fitting and the insertion depth aligns with the edge of the fitting. Select the correct jaw and fitting and press the jaw/rig around the pipe, forming a right angle with the pipe. Close the press jaw around the pipe and hold the trigger. The jaws will release when the larger pipes have an actuator that will be released when the connection is complete.
Side-by-Side Comparison
The Importance of Choosing the Right Fitting
Uponor ProPEX® cold-expansion fittings are the right choice for any project because they offer a unique, simple, reliable, and visually verifiable connection that does not require heat or open flames and eliminates the possibility of dry fits. The flexibility of PEX-a eliminates the need for a connection at each change of direction to boost jobsite productivity and material savings. This system is based on shape memory, allowing these fittings to create a strong bond with the pipe – one that can withstand 1,000 pounds of radial force.
