by Marty Alan McGill

Created on: March 19, 2007   Last Updated: April 27, 2007

When you hear the word "Sweating", what do you think of? Most people think of perspiration, which is the logical answer. Of course plumbing is not always logical, so let's explore another meaning of the word.

In plumbing terms sweating is the procedure used to join copper pipe together using copper and/or brass fittings. Most people know it as soldering, yet plumbers and pipe fitters call it sweating. It is done under the intense heat of a hand-held torch, usually propane or the hotter burning MAPP gas, although acetylene, or any hot burning gas will work.

If you're doing plumbing repair work, it is crucial that you have NO water in the pipes. You can hold a torch on a pipe full of water all day long and not make it hot enough to melt solder. Drain the system thoroughly, from the lowest point you can find. This is usually an outside sill-cock. Be sure and open faucets in the house to allow for proper drainage.

The most important step in sweating copper pipe is the cleaning of the pipe and fittings. Sand the pipe with emery cloth until it shines, and use a fitting brush to clean the inside of the fittings. You can use the emery cloth if you don't have a brush. This is a critical step, as any foreign substance can cause the joint to fail.

Next, brush a light coat of "flux" on both the fitting and the pipe. This is what causes the solder to flow into the joint, and it will not work without it. Put the joint together and you are ready to sweat.

Heat the pipe and fitting with your torch until you notice a green glow in the flame. This should indicate that you are ready to apply the solder. Touch the solder to the joint, and it should flow right into the joint. When it drips out the bottom, stop.

Let the joint sit untouched for several seconds to insure that you don't break it loose. At this point, take a damp rag and wipe the joint to clean up excess flux and soot. This step will make a very shiny, and nice looking joint ... and you should always take pride in your work.

You should be able to put the water, air, or whatever on the joint now. If done properly, a sweat joint is virtually leak proof and forever.

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