Soldering Copper Pipes
Basics
Soldering copper pipe, or "sweating" as they call it in the trades, relies on capillary action to create a well-sealed joint. By using a propane torch to heat up the two pieces you are joining, solder is "sucked" into the joint and spreads evenly between the pipe and fitting. Once it cools, you should have a solid, leak-free joint that will last for years.
Use care when working with a torch. Keep the flame away from wood framing or other flammable materials. Also remember to let your work cool before handling it.
Plan ahead. Determine all the materials you will need to complete your plumbing project. Make sure you have enough copper tubing and fittings to make all your turns and straight runs. The last thing you want to do is run to the hardware store in the middle of a project.
Before cutting new pipe, consider the makeup distance (length of the part that will go into the fitting). Cut new lengths of copper pipe with a tubing cutter designed for copper. To use the cutter, twist the knob until the cutter wheel makes contact with the surface. Rotate the cutter around the tube, tightening after each revolution until the pipe easily snaps in two.
After you have cut the tube, clean the inside from burrs with a round brush file or with the retractable reamer often found on tubing cutters. Burrs can cause pipe friction, so reaming them out helps ensure a smooth flowing joint.
Next, use an emery cloth, steel wool or sand paper to smooth and polish the last inch of the outside end of the pipe until it is shiny. Do not overdo this. Also, clean the inside of the fitting from the end down to the shoulder (point where it bends) You can use an emery cloth or steel wool but you will find that a pipe brush makes cleaning easier.
To ensure flow of the solder, use a small stiff brush to apply flux around the inside of the fitting and around the outside of the pipe end. Place the fitting on the pipe end and turn the pipe or the fitting back and forth once or twice to spread the flux evenly. Then position the fitting correctly. It is best to wear gloves for this part to prevent chemical injury to your hands.
Turn on the gas torch's control value and then light the nozzle end with a striker tool. Adjust the flame so it is steady and strong, making certain that it is not aimed at anything flammable. If necessary, shield surround objects with a flame guard.
Next position the torch nozzle about 4 inches from the fitting and move the flame back and forth to distribute the heat evenly. It is important to get the fitting hot but not too hot; the flux will burn and simply vanish if it is over-heated. Be careful where you hold the pipe, as it will become hot.
You'll know if the joint is hot enough when the solder melts on contact with it. Test the temperature by touching the solder wire to the joint occasionally as you heat the fitting. The instant the wire melts, the joint is ready for action.
Turn off the torch, and touch the solder wire to the edge of the fitting; capillary action will pull molten solder in between the fitting and the pipe. That's right! It will actually suck it into the joint. Keep applying the wire until the line of molten solder show all the way around the fitting. Once the solder cools (in just a few minutes), wipe the excess flux off with a damp rag.
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