How to Sweat/Solder Copper Pipe


While a lot of plumbing is moving toward plastic pvc pipes chances are that at some point in your life you will deal with copper pipes and understanding how to solder is essential. To help you get on your way and to work let’s run through the basic steps of soldering.

1. Collect Your Tools

Before you get to it make sure that you have a propane torch, flux, solder, steel wool, plyers, protective eyewear, a pipe brush and an application brush. Have these on hand and ready to go. Check that there the torch has enough propane it (having your torch run out in the middle of a job can be a huge pain).

2. Clean off the Pipes

If you look at your copper pipes in the basement you will see they have discoloration and dirt all over them. Wipe off the pipes with a rag and then take a handful of steel wool and rub the ends of the pipes you are going to connect. Even if you are installing new pipe make sure to rub the steel wool along the end of the pipe for a good 2-3 inches. As you rub the steel wool on the pipe you will see a shine to the pipe as the dirty outer layer has been scraped away. Hopefully you also have a small wire brush that you can use to slide inside the pipe and rub back and forth as well as twisting to get the same shine on the inside of the pipe as you did on the outside with the steel wool. There are different size brushes for different size pipes, make sure you get the right size otherwise you may end up ruining your brush. Clean the outside and inside of both pipes (not necessary for both but will save you time in case you mixed up which pipe is connecting to which).

3. Lay the Flux

Take a brush and dip it into your flux dish and rub flux around the outside edge of both pipes (I usually use my finger and a rag instead of a brush but a brush leaves less mess). Also place some flux on the inside of the fitting where the two pipes will be inserted. You can also use your steel wool on the fitting before laying down the flux if you wish.

4. Connect and Sweat the Pipes

Slide both pipe ends into the fitting and make sure that it is nice and tight. Now that the pipes are connected take your blow torch and adjust it to a low blue flame. Move the flame back and forth along the joints where the pipe and connector meet. If you need to touch the pipe make sure to use plyers as the heat will conduct very quickly along the metal. This heating of the pipes is referred to as ‘sweating.’

5. Solder the Pipe

After the pipe is heated up take your solder wire and pull out a good five inches off ream and hold the ream with the solder wire forming a straight line. Take the blowtorch away from the pipe and lay the solder gently against the heated edge of the pipe and the connector. The solder will melt and run along the flux that you laid on the pipe. Make sure the solder creates a seal all the way around the pipe and use your solder wire to smooth any drips or bumps in the seal. You don’t need a bunch; just a thin layer along the connection. For heaven sake make sure that you are never soldering directly above your face as the solder will drip down and burn you (personal experience). Also wear protective eyewear. If the pie was not hot enough for the solder to run heat the pipe more and test with the edge of your soldering wire. You will get the hang of it after a few runs.

6. Let the Pipes Cool and Clean them

After the pipes have cooled off go ahead and take steel wool to wipe any excess solder and a rag to wipe off any discoloration of the pipe that may have occurred during heating (if you heat the pipe to much the bluish discoloration will be permanent). Collect your tools and you should be done, make sure to run the liquid, gas, etc. back through the pipe and check for any leaks. With gas spray soapy water on the connection and make sure not bubbles appear from leaking gas.

On a side note if you are having a plumber or general contractor replace your old copper piping with pvc pipe make sure to keep the copper yourself rather than letting them walk away with it. Copper can sell for a good price at scrapyards or metal works.

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