How to Sweat a Pipe Joint

Correctly sweating pipe provides a secure connection that is water-tight.

Sweating a copper pipe joint is not as difficult as many people believe. Copper pipe is an ideal choice for water supply lines because it is lightweight. Unlike threaded pipe, copper pipe requires sweating to form a tight seal between the pipe and coupler fittings. Sweating is a process of melting solder into the seam of the connection. The key to sweating a pipe joint successfully is preparing the pipe. Solder kits that include a propane torch, solder and flux are available at home improvement centers.

Things You'll Need

• Tape measure
• Pipe cutter
• Sanding cloth
• Rag
• Flux
• Portable propane torch
• Striker
• Solder

Instructions

1. Measure the copper pipe and cut it with a pipe cutter. Pipe cutters clamp around the pipe and help ensure the cut is square. When measuring and cutting, remember the contractor's rule: “Measure twice and cut once.”

2. 

   Pipe cutters maintain a level cut.

   Remove burrs from the inside of the cut pipe with the reaming tool on the pipe cutter. The reaming tool is the triangular piece of metal on the outside body of the pipe cutter. Once the straight pipe is cut and reamed, dry-fit the pipe joint over the end to ensure the pipe seats inside the joint shoulder. The shoulder is the portion of each end of the pipe joint that is slightly larger in diameter than the rest of the fitting.

3. Clean the last 4 inches of the end of the copper pipe with a strip of sanding cloth. Continue sanding the end of the pipe with the sanding cloth until it shines like a new penny. Sand the edge of the pipe and also inside the pipe joint shoulder with the sanding cloth. Wipe the end of the pipe and inside of the joint with a clean rag.

4. Open a can of flux and mix it well with the flux applicator brush. Brush the flux over the end of the pipe and inside the pipe joint in a thin, even film. Insert the end of the pipe into the pipe joint. Unroll 1 foot of solder from the roll so it is straight.

5. Turn the dial on a portable propane torch clockwise until you hear the gas. Hold the cup of the striker tool an inch in front of the torch and squeeze the handles to create a spark. This spark ignites the gas. Adjust the dial on the torch until you have a small blue flame in the center.

6. Hold the flame of the torch over the seam of the joint and sweep the flame back and forth. Continue heating the joint until the flux begins to bubble. Hold the roll of solder in your free hand and touch the tip into the joint seam. The tip will melt and seep into the entire circumference of the seam.

7. Turn off the propane torch and set it down. Gently wipe the seam of the joint with a clean rag. Use care, when wiping, as the copper pipe is still very hot.

Tips & Warnings

• Practice sweating on some scrap pieces of copper pipe to get a feel for the process.

• Always wear thick leather gloves, when soldering, to protect your hands from burns.

References

• Popular Mechanics; Plumbing Basics -- How to Sweat a Pipe Joint; Pat Porzio