Connecting two pieces of copper pipe is an important skill that all DIY plumbers and home repair enthusiasts must learn to master. "Sweating" refers to the process of heating the cut end of a copper pipe and a connecting piece until solder melts and flows between the two, forming an impenetrable bond between them. Although sweating copper pipe is usually a job for a professional plumber, you can learn this important skill with a little practice. Here's a look at how you can master this important plumber's secret and make a connection that will last without leaking forever.
There are only a few tools you will need to sweat copper pipe. A pipe cutter and a propane torch are the primary tools, but you will also need a plumber's solder, a damp rag, sand paper and soldering paste, or flux. If you are planning on making your connection anywhere near anything flammable, such as a floor joist, wall stud, or inside a kitchen cabinet, you should also have a flame deflector. You can easily make your own flame deflector from an empty coffee can or some type of metal plate. It's always a good idea to have a portable fire extinguisher nearby whenever working with a propane torch.
Once you have measured the length of pipe and the connectors you need, use the copper cutting tool to cut the copper pipe to the proper length. You want a nice, clean cut that is free of any burrs inside or out. If you haven't used a cutting tool before, you should practice making a clean cut a few times before working on the real plumbing job. Burrs on the inside of the pipe can be removed with a half-round file. Burrs on the outside of the pipe can be removed with a small piece of medium grit sandpaper or an emery cloth.
Next, use the sandpaper or emery cloth to burnish the outside of the copper pipe and the inside of the connector. Using a cotton swab or a clean cloth, apply a thin coat of soldering flux to the outside of the pipe and the inside of the connector. Insert the pipe into the connecting piece and wipe off any flux that oozes out. Flux removes any impurities that might be present on the copper pieces, and only a small amount is needed for it to its job.
Connectors come in many different sizes and shapes, such as an elbow bend a 45-degree bend, a "T" connector or a connector for joining two sections of pipe together. Be sure to have the right sized and shaped connector for the job at hand before beginning your work. Your pipe and connectors should be clean and dry before you apply heat to the copper pieces.
Sweating begins when heat is applied, first to the copper pipe and then to the connector. Being careful of the direction of your flame, begin applying the torch's flame to the copper. A propane torch comes with different tips for different purposes, but any tip will work as long as you don't overheat the copper. Overheating copper is the main mistake a novice plumber will make. Working with copper is not like working with iron in a forge, just a small amount of heat will work nicely.
Apply just enough heat to melt the flux, which will occur at a relatively low temperature, and to melt the plumber's solder. When both the copper pipe and the copper connector are heated uniformly to slightly more than 140 degrees F., the solder will melt and flow quickly in between the pipe and the connector, making a solid, leak proof connection. As with learning the proper pipe cutting technique, practicing sweating copper pipe and connectors together at the workbench will prove beneficial when it comes time to do the real job.
Once the solder has flowed into the connection, withdraw the flame and wipe the excess solder off with a damp rag. A clean joint is a sign of a professional job, well done. If your copper is blackened, it has gotten too hot, if the solder has beaded up, is discolored or appears to drip out, the joint may leak shortly after you turn the water on. Make a proper solder connection right the first time and you will save yourself the plumber's headache of trying to make a good connection with water in the line.
The best advice for leaning how to sweat copper pipe is to practice a bit in the workshop. You will soon see how easy it is and how much heat, flux and solder you need to make a secure connection that will last without leaking, forever.