How to solder copper tubing?
A first glance, soldering together copper tubing and fittings seems like a messy job. You have dirty pipes, greasy flux, and dripping solder at nearly every turn. But the connecting points between tubing sections and fittings are anything but dirty. In fact, the most important step in sweating joint is to make sure all mating parts are clean before any flux, solder, or heat hits the joint. Specialized tools make this job easier. But don't forget, you can get good results with nothing but a pad of steel wool.
The tools and materials you'll need are: cleaning tool or pad, flux & brush, tubing & fittings, solder, rag, gloves & goggles, soldering torch.
Step 1: Use a combination tool, wire brush, or abrasive pad to clean the inside of each hub on the fitting. Combination tools come with one end for cleaning the inside of the fittings and a round recessed brush for cleaning the outside of the tubing. Tools are available for 1/2- and 3/4-dia. tubing.
Step 2: Use the tubing brush in the body of a combination tool to clean the ends on all tubing sections. Keep turning the tool until a 1-in.-long strip at the end of the tube is shiny. With a little more elbow grease, you can clean the tubing with an abrasive pad (inset photo) or steel wool.
Step 3: Once the mating surfaces are clean, spread flux on the inside of the fittings and around the outside of the tubing using a small disposable brush. Then push the tubing into the fitting.
Step 4: Because you have to handle the solder with one hand and torch with the other, it's a good idea to pull about 24 in. of solder from the roll and wrap it around your hand, Holding solder this way and advancing it into the joint is much easier than struggling with a tightly wound roll of solder.
Step 5: Shutoff valves are standard fittings used for regulating water flow through out the system. Most feature some rubber and/or plastic parts. These will be damaged when the fitting is soldered unless you remove the valve stem first. Use an adjustable wrench, and turn the stem counterclockwise.
Step 6: Start soldering at the lowest point. Adjust the torch flame so that the tip id blue colored, and direct this tip alternately to both sides of the fitting. Unroll a length of solder, and press it against the joint on the fitting and tubing. When the fitting is hot enough, the solder will melt and be drawn up into the joint.
Step 7: Joint are complete when they don't draw in more solder and any new solder starts to spill out. Once this happens, immediately wipe away any excess with a damp rag. If you wait for even 10 seconds, the solder can cool and harden, and you won't be able to wipe it away.