The simple answer is that sweating a copper water pipe joint is not difficult. I believe that given the proper tools, some helpful tips, and practice, anyone can do it successfully. Having said that, I recommend that you get a copy of my book, "Remodeling a Bathroom," and dive into chapter 3, "Rough-In Plumbing." On pages 56-59 I clearly outline the procedure with detailed photos.

Safety is your first consideration when soldering. Wear gloves, a long-sleeved shirt, and eye protection to prevent burning yourself. Never stand under a joint when soldering. Instead work off to the side from a stepladder to avoid being in the path of hot solder if it should drip. Also protect flammable surfaces from the torch flame by creating a heat block with a fireproof pad or a double layer of 26-gauge sheet metal.

Soldering or sweating copper fittings is a process that involves heating the fitting and pipe to a temperature high enough to melt the solder and draw it into and around the joint.

Use a top-quality tubing cutter for clean cuts on pipe to be soldered. After the pipe has been cut, deburr the inside of the pipe. If the pipe or copper fitting has dents or depressions, cut off the damaged area of the pipe and/or throw the fitting away. You may need to cut a new length of pipe.

Good soldered joints require absolutely clean mating surfaces. Use a quality four-in-one cleaning tool to clean at least the depth of the fitting but not less than 1/2 inch of the outside of the pipe and the inside of the fittings with its 1/2-inch or 3/4-inch brushes. If the copper is dirty, the solder will ball up and adhere to itself, not to the copper. These areas cause voids in the soldered joints and create leaks in the system.

Water in the lines will prevent you from getting the joint hot enough to accept the solder, causing the solder to lump up on the pipe. Even with the water turned off and the lines drained, water can still be in the lines. One trick is to plug the existing pipe(s) with bread; it absorbs moisture and will disintegrate when the water is turned on.

After cleaning all the parts (even those that are new from the store), apply lead-free "water-soluble" flux with a clean brush in a thin even layer to the outside of the copper pipe and the inside of the fitting. Use only enough flux to properly cover the surfaces to be joined. Too much flux interferes with the soldering process; too little prevents the solder from running up the joint and around the pipe.

Assemble and align the pipe and fitting so they are straight and square. They should be supported horizontally and vertically (with string or wire) while you are soldering to prevent misalignment at the next joint down the piping path.

Use a portable hand-held torch with a pencil-flame orifice to heat the fitting (not the pipe). Hold the flame far enough away from the fitting so the sharp point of the inner cone of the flame just touches the metal. The larger outer envelope of the flame will then evenly spread the heat.

While heating the area to be soldered, touch the joint with lead-free solid-wire solder from time to time to see if it melts (not into the flame). When the solder begins to melt, even a little, move the flame to the heel (center) of the fitting. Once the joint is hot, pull the flame away and touch the solder on the joint at one location. There's no need to move the solder around the joint; the flux will help draw the solder up, in, and around the joint. Overheating the joint will allow the solder to run through without creating a seal.

Try your hand on a dummy piece until you achieve a solid leak-proof bond between the pipe and fitting. It's trite but true: practice makes perfect.

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C.R.S., Inc. · Spokane, Washington · USA