How to Solder Copper Pipes

Plumber soldering pipes
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While there are many home improvement or repair projects that are best left to trained and experienced professionals, soldering and replacing copper pipe in your house doesn't have to be one of them. The soldering process looks a bit intimidating as a beginner do-it-yourself project, but it is a fairly simple process, as long as you follow a few basic instructions.

Note that it is imperative that you follow the safety instructions throughout this tutorial.

Supplies Needed

  • Eye protection
  • Heavy gloves
  • Fire protection cloth
  • Fire extinguisher
  • Copper pipe
  • Copper pipe fittings
  • Tube cutter
  • Deburring tool
  • Wire brush
  • 120-grit emery cloth, sandpaper, or fine steel wool
  • Propane torch and regulator with built-in igniter
  • Lead-free soldering paste (also known as “flux”) with flux brush
  • Solder wire
  • Rags

Prepare the Pipes and Fittings

Before beginning any part of this project, be sure to put on eye protection.

Cut the Pipes to Length

  1. Clamp the pipe between the cutting wheel and the guide wheel of the tube cutter. For longer pipes, tuck the other end under your knee to hold it stable.
  2. Rotate the cutter to score the pipe all the way around.
  3. Tighten the cutter knob one quarter-turn. Score the pipe all around again; this will make a slightly deeper scoring line.
  4. Tighten the cutter knob another quarter-turn and score the pipe a third time. Continue to tighten and score until the pipe snaps off; this will take about eight turns.

    Clean and Flux the Pipes and Fittings

    1. Use the deburring tool or wire brush to ream the inside of the pipe. A burr is a small ridge of copper that forms when it is forced into the pipe when you are cutting it. If you don't remove it, it can impede the flow of water through the pipe or cause leaks.
    2. Use the emery cloth, sandpaper or steel wool to clean the outside of the pipe and the part of the fitting that will join with the pipe. When it is clean, the pipe should be shiny. Once this is done, don't touch the pipe with your bare hands so that you don't leave body oils on the surface. This can interfere with the solder setting without leaks.
    1. With a brush, apply a thin layer of flux to the last inch of the pipe.
      Safety Tip: Do not apply flux with your fingers! It is an acid and can cause injury to skin, eyes, and other soft tissues.
    2. Apply flux to the inside surface of the fittings where they will join the pipe.
    3. Push the pipe into the fitting until it is seated all the way to the full depth of the fitting.
    4. Wipe off any excess flux with a rag.

    Solder Pipes and Fittings Together

    Put on your heavy gloves before starting these steps, and be sure you are still wearing eye protection. Be sure you have a fire extinguisher nearby, just in case.

    1. Cover any flammable surface near your work area with fire protection cloth.
    2. Cut about 8 to 10 inches of solder wire; bend the last 2 inches at a 90-degree angle.
    3. Light the propane torch using the built-in igniter.
    4. Adjust the blue cone of the flame to about 1 1/4 inches.
    5. Hold the torch so that the tip just touches the fitting. Move it back and forth to evenly heat the fitting. You don't need to heat the pipe with the torch; the heat from the fitting will take care of that. You should hear the flux sizzle as the metal heats up.
    6. Place the end of the solder wire at the joint, on the opposite side of the fitting from the torch flame. As the metal gets hot, the wire will liquefy, flowing into the joint to fill the space.
    1. Fill the joint until the solder begins to drip out; it will take about 1/2 to 3/4 inch of solder wire, depending on the size of the pipe and fitting.
    2. Allow the soldered joint to cool 30 to 45 seconds before applying any kind of pressure. Wipe away any excess solder.
    3. Install the pipe and test it for leaks. If it does leak, remove it and take the pipe and fitting apart, then resolder them.

    If you are soldering pipe that is already in place, be sure to drain any water and thoroughly dry the interior before soldering; the propane torch can help speed that along, if applied carefully.