How to Sweat Copper to Fix a Leak

Use solder wire and a torch to sweat copper fittings.

If you discover a small leak in your copper piping and need to replace a short length of the pipe, you may be able to solder a coupling to the existing, undamaged copper piping. A coupling, available at hardware and plumbing stores, is a length of copper pipe designed to bridge the cut ends of pipe together. Measure the diameter of the pipe before purchasing the coupling to get the right size. The coupling needs to be slightly larger in diameter than the existing pipe.

Things You'll Need

• Marker or tape
• Bucket
• Pipe cutter
• Cloth
• Coupling
• Wire fitting brush or steel wool
• Plumber's sandpaper
• Plumber's flux
• Solder wire
• Hand-held propane torch

Instructions

1. Locate the damage on the pipe and mark it with a marker or piece of tape. Turn off the water supply to the house. Turn on the faucets throughout the house to remove as much water as possible from the pipes.

2. Place a bucket or other container beneath the damaged pipe. Measure approximately 1 1/2 inches to either side of the leak and mark the distances. Use a pipe cutter to cut the damaged length of pipe from the rest of the copper piping. Use the bucket to catch any water left in the pipe. Dry the interior of the pipes with a clean cloth.

3. Measure the gap of the cut. Measure out that length plus 1 inch on the repair coupling and mark with a marker or piece of tape. Use a pipe cutter to cut the repair piece from the coupling.

4. Use a wire fitting brush, a wire brush small enough to fit inside copper piping, or steel wool to clean the interior of both ends of the coupling. Use plumber's sandpaper or fine-grit sandpaper to clean and roughen the exterior of the coupling. Use a clean, dry cloth to wipe down the interior and exterior of the coupling as well as the exposed ends of the existing copper pipe. Ensure all components are clean and dry.

5. Apply a small amount of plumber's flux to the interior and exterior ends of the coupling with a small brush, covering approximately a half-inch with the flux at each end. The plumber's flux acts as a conduit during the soldering process, pulling the solder into the joint.

6. Slide the repair coupling over one end of the existing pipe and gently work the other end of the coupling onto the other end of the existing pipe. You may need to loosen the closest pipe clamp to get the coupling over the end. Ensure the coupling is centered on the gap, then tighten the clamp.

7. Hold the tip of the solder wire to one side of the first joint you intend to solder while simultaneously holding the tip of the propane torch to the joint. You should see the solder wire start to melt and bubble, sweating into the joint between the coupling and the existing pipe. Move the solder wire around the joint to create a good seal.

8. Continue to heat the solder wire with the torch, ensuring enough solder is melted into the joint to create a strong connection. Repeat the process on the other joint.

9. Allow the repair to cool completely before turning on the water to the house. Turn off the faucets in the house and check that the repaired joints are sealed.

Tips & Warnings

• If the soldering isn't sweating into the pipe, remove the coupling and wipe away any moisture trapped in the pipes or coupling. Apply plumber's flux to the coupling, fit the coupling and re-solder.

References

• The Family Handyman: How to Repair a Leaking Copper Pipe
• "Popular Mechanics"; Plumbing Basics--How to Sweat a Pipe Joint; Pat Porzio; 2007

Resources

• "This Old House" magazine; How to Use Torches, Heat Guns, and Soldering Irons--and When; John Kelsey