How to Transition From Copper to PEX
Mastered in a Minute: Sweat adapters create a solid connection between copper and PEX supply lines.
Transitioning from copper to PEX is a common thing to do when adding new supply lines to an existing home. Sweat adapters make this transition simple.
Female sweat adapters come in many varieties for different kinds of PEX fitting systems (check out the article “Connecting PEX Plumbing” for a rundown of the major PEX fitting systems ). These adapters are soldered—or “sweated”—onto the copper tubing, allowing for a solid connection between the copper and the PEX. Here we’ll use an adapter designed to transition from copper to a PEX crimp connection.
Start by cleaning the outside of the copper tubing with plumber’s cloth, and the inside of the fitting with a wire brush. Then, use an acid brush to apply tinning flux to both the outside of the copper and the inside of the fitting. Then slip the fitting onto the tubing with a slight twist, making sure it’s fully seated.
Unroll about 6 in to 8 in. of lead-free silver solder and bend it at 90° about 2 in. from the end to make it easier to solder around the joint. For 1/2-in. tubing, you’ll only use about 1/2 in. of solder per joint.
Heat the fitting at the connection with a torch, keeping the tip of the brightest part of the flame in contact with the surface. The heat will transfer through the fitting to the pipe.
Soon after the flux starts to bubble, test to see if the tubing is hot enough by touching the tip of the solder to the copper where it meets the fitting. Once it’s hot enough to melt the solder, remove the flame to avoid overheating, and touch the solder to the top of the joint. The solder will run down and around the joint and be sucked into the fitting by capillary action. You can also run the solder around the joint—the hook makes this easier.
With the solder still molten, use a dry rag to clean up any excess solder. When it’s cool, connect the PEX to the end of the adapter. With this crimp fitting, slide the crimp ring onto the PEX first, then push the PEX onto the adapter, slide the ring over so that it’s about 1/8 in. from the end of the tubing, and crimp it with a crimping tool.
For more on cutting copper tubing and PEX fitting systems, check out:
- How to Cut Copper Pipe
- Connect PEX With Viega PEX Press Fittings
- Connect PEX With Crimp Fittings and Stainless-Steel Clamps
- Connect PEX With ASTM F1960 Expansion Fittings and ProPEX Rings
- Connect PEX With ASTM F2080 Expansion Fittings and Compression Sleeves
- Connect PEX With Push Fittings
- Connect PEX With Crimp Fittings and Crimp Rings
- Connecting PEX Plumbing