How to Solder Copper Plumbing Pipe / Fittings.
(How to Sweat Copper with a Propane Torch)

Using copper for water supply pipe for your home offers some advantages over threaded galvanized iron pipe. Threaded pipe can be difficult to work on because once the system has been all threaded together, it is more difficult to make additions or changes to it (you can’t just unscrew a section of pipe once it has fittings already threaded to each of its ends, since turning the pipe one way to unscrew it causes it to screw in tighter on its opposite end). With copper, you just cut out a section using a simple tool (see below), and solder in a new section. Soldering, when done correctly, also makes leaks a very rare occurrence.

In addition to being easier to work with, copper pipe has a longer life than galvanized iron pipe, which will inevitably rust from the inside out. This rust tends to clog faucet aerators and valves with its debris, and will eventually cause the pipe to develop leaks or to break.

The propane torch is the primary tool used to solder copper fittings (soldering copper pipe is also referred to as "sweating copper pipe"). Shown here is a typical torch that has just been lit with the pictured flint torch lighter (using this type of inexpensive lighter is safer and easier than using a match or butane lighter). You can often buy a torch similar to the one shown as part of a kit that includes soldering wire, flux, a lighter, and some other accessories. Once the propane cylinder is empty (they last for a very long time), you simply screw the brass torch head to a new propane cylinder. For more money, you can buy a torch head with a built in ignitor, which is quite convenient. NOTE: Avoid using MAPP gas for soldering. It burns hotter, and while some professional plumbers prefer it, it cannot be used to much advantage by the amateur.)

Flux and soldering wire is also used with the torch when soldering. The two types of flux most often used for sweating copper pipe are paste flux and liquid flux. The purpose of applying flux to the copper fittings is that it cleans away the oxidized coating on the metal and allows the liquid solder to flow and bond to the surfaces. I prefer the use of liquid flux, but sometimes it can be hard to find depending on where you live. An inexpensive flux application brush is used with either kind of solder. Be sure to buy flux and soldering wire that is intended for residential copper plumbing (it is the most commonly available type, so it will not be hard to find).

The most physically demanding part of soldering copper is cutting the pipe sections. Although I might add that this is by no means as physically demanding as working with pipe wrenches and galvanized threaded pipe. The tool shown has a cutting disk that scribes the pipe as the tool is rotated around the pipe (in this image you can just make out the bright line where the cutting wheel is biting into the metal). After a couple of rotations, the knob at the bottom of the tool is tightened slightly, driving the cutting disk a bit more deeply into the copper, and then the tool is rotated again. This process is repeated until the pipe finally snaps apart. The amount of time it takes depends on how tightly you rotate the knob -- the tighter the knob, the deeper the cutting wheel bites and the harder it is to rotate the cutter around the pipe, but the faster it cuts.

Once the cut pipe snaps apart, you want to de-bur its inside edge using the deburing blade on the cutting tool. Simply stick this triangular blunt edged blade into the pipe, and forcefully rotate the pipe and the tool to smooth out the turned-in bur of copper that resulted from the cutting process. This reduces the chance of turbulence and noise developing within the pipe as water is flowing through it as part of your plumbing system.

If you need to work on pipe that has already been installed in a house, a second pipe cutter like this is often a necessity. It works on the same principle as the one illustrated above, but it is smaller so that it can fit into tight places, such as when you need to cut a copper pipe that is running through a stud wall or close to a floor joist. In those instances, using the larger cutter would be impossible because there is not enough room for it. The advantage of the large cutter is that its bigger size offers far more leverage, making it easier to use. If you use one of these small cutters for an extended time, you will find that your fingers get quite sore from rotating it around the pipe so that the cutting wheel can do its work.


Wire brushes made specifically for cleaning copper pipe can also be useful, although not essential, especially if you are using fairly new copper fittings that have been stored in a relatively clean environment. Older, dirtier pipe and fittings that have a heavy layer of oxidation on them can benefit from the use of wire brushes though. The brush shown is one designed for cleaning the inside of copper fittings, but there are ones made for cleaning the ends of copper pipe as well.

PAGE 1 -- PAGE 2 -- PAGE 3
The informational content of this how-to website is not warrantied in any way or form, and any use of said content are at the reader's own risk, the author shall not be held responsible in any way for any damages or injuries arising from the content of this web site. Common safety practices are encouraged at all times, and the proper and safe use of all power tools and safety equipment (eye goggles, etc.) is the responsibility of the user. Additional How-To articles Here.
Copyright 2008 Thomas Penrose