Pro Tips on Soldering Copper Pipe
Updated: Nov 2, 2020
As I was preparing a story on installing a whole-house water filter, it occurred to me that we had not yet touched on soldering copper pipe here at HIR magazine. Although push-fit PEX plumbing connections are now making a splash among DIY'ers for their ease of use, those connections can be expensive, and many pros still prefer the old-fashioned reliability of a properly soldered pipe.
Rather than regurgitate the tried-and-true instructions for how to solder a joint, I'll turn to the industry experts at the Copper Development Association, which offers a series of short, free instructional videos that demonstrate the process. -- M. Weber
How to Solder Copper Pipe (2:53) -- This video shows the basics of soldering...
Types of Tube and Preparation (2:47) -- This video covers types of copper tubing, how to correctly measure and cut copper tubing, and common pitfalls to avoid before soldering.
Soldering No-lead Fittings (11:24) -- This video shows how to solder copper tube and fittings to the newer, no-lead, brass and bronze copper alloys as a result of the new Federal Reduction of Lead in Drinking Water Act.
Step-by-step Soldering Instructions
1. Measure and mark the copper pipe with a pencil, allowing for the length of pipe that fits into the fitting cup. Dry-fitting the pipe and fittings before soldering will ensure the fittings are square and the runs straight.
2. Cut the pipe to the measured length using a disc-type tube cutter, a hacksaw, an abrasive wheel, or with a stationary or portable band saw. Be careful not to deform the pipe while cutting. Regardless of the method, the cut must be square so the pipe will seat properly in the fitting cup.
3. Ream all cut pipe ends from the inside diameter to remove the small burrs created by cutting. A properly reamed pipe provides a smooth surface for better water flow. Also remove any burrs on the outside of the pipe to ensure proper entrance into the fitting cup. Use the reaming blade on a pipe cutter, half-round or round files, a pocketknife or a suitable deburring tool. If using soft pipe (annealed), be very careful to not deform the pipe end by applying too much pressure.
4. Clean off all oxides and surface oil from the pip end and fitting cup. This will allow the proper flow of solder into the joint. Lightly clean the pipe end using sand cloth or nylon abrasive pads slightly beyond the depth of the fitting cup. Clean the fitting cup by using abrasive cloth, abrasive pads, or a proper-sized fitting brush.
5. Apply a thin, even coat of flux with a brush to both the pipe and fitting as soon as possible after cleaning. Do not apply the flux with your fingers, because chemicals in the flux can be harmful if they come into contact with the eyes, mouth or open cuts. Apply the flux carefully, because residue from excess flux can cause corrosion.
6. Insert the pipe into the fitting cup, making sure it is seated against the base of the fitting cup. Twist it slightly to ensure even coverage by the flux and wipe away excess flux with a cotton rag. Support the pipe and fitting assembly to ensure even connection around the joint.
7. Using a hand torch, begin heating with the flame perpendicular to the pipe, which conducts heat into the fitting cup. Preheat the entire circumference of the pipe to bring it up to a suitable temperature. (For joints in the horizontal position, avoid directly preheating the top of the joint to avoid burning the soldering flux.) Next, move the flame onto the fitting cup. Sweep the flame alternately between the cup and the pipe a distance equal to the depth of the fitting cup, preheating the circumference of the connection. Touch the solder to the joint. If the solder does not melt, remove it and continue heating. Avoid overheating the joint or directing the flame into the face of the fitting cup, which could burn the flux and destroy its effectiveness. When the solder melts, apply heat to the base of the cup to aid capillary action in drawing the molten solder into the cup toward the heat source.
8. Allow the completed joint to cool naturally. (Cooling with water may stress the joint.) When the joint is cool, clean off any remaining flux residue with a wet rag.
Check out more instructional videos and articles on soldering copper at CDA's YouTube channel.