How to Sweat a Pipe Coupling

Blue pipes.
  • 2-3 hours
  • Intermediate
  • 20-60
What You'll Need
Soldering iron
Pipe cutter
Wire brush
Copper pipe

If you’re going to do much plumbing you’ll need to learn how to sweat a pipe coupling. Solder makes a good, watertight bond on copper pipe and you’ll inevitably work with copper pipe. By knowing how to sweat a pipe coupling you’ll be ready to tackle most household plumbing jobs. It’s not difficult to learn.

Step 1 - Prepare

Preparation is key to soldering. Start by using a pipe cutter to make a clean break in the pipe. Tighten and turn around the pipe until it breaks and then use the reamer to clean out the burrs from inside the pipe. Use a wire brush on the outside of the pipe where you’ll be sweating the joint coupling to take off all the oxidation on the pipe. Roughen beyond the area where you’ll be working and then be certain to remove all the grit with a clean cloth.

Step 2 - Flux

Use enough flux on the joint. Brush it all over the area where you’ve used the wire brush. If you’re going to be soldering where you can’t see all around the joint, try taping a small mirror in place so you can see the backside of the joint. If the pipes are in place, make sure that the water is off before you work and that the fixtures have been emptied. To ensure that no water touches the solder as you’re working, which you really don’t want, put a little bread down the pipe from the water supply. This will absorb any water. When you do finally run the water the bread will disintegrate.

Step 3 - Solder

Start by dry fitting the connections to be certain they fit well. Put the fixture in place and begin to heat. You’ll achieve the best result by playing the blue part of the flame over the copper. Exercise some patience when heating; don’t expect it to be ready to work immediately.

Hold the solder in place once the temperature is right. The fixture will begin to suck the solder. Go slowly to make sure you have a complete bond all around the joint. Failure to do so will mean a leaking joint and you’ll need to disassemble everything and redo it. Taking a few minutes more now can save a great deal of work.

Step 4 - Finish

Allow the joint to cool naturally. Don’t use water on it to speed the process as it can cause damage to the joint you’ve just made. Don’t begin to try and fit the joint together until the metal is completely cool.

After you’ve fitted the joint and you’re ready to turn the water back on, remove all aerators and filters from the faucet. This will allow the bread and any burrs and debris to wash out cleanly. Run the water until everything has flushed through. This will also allow you to check the strength of the solder you’ve put on the joint and see if you’ve sweated the pipe joint properly.