May 19, 2025
How to Make a Cold Expansion Connection
By Alex Gross
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 retract to its original size.
Making a cold expansion connection is simple:
2. Slide the PEX ring, with the stop on the front, onto the end of the pipe.
3. Insert the expansion tool and hold the trigger to allow for several expansions.
4. Ensure the head is rotating with each expansion.
5. Place the pipe and ring up to the stop on each 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, boosting 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.
Trusted. Proven. ProPEX®
Push-to-connect system requiring no heat, open flame, glues or dry fits.
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