How to Solder a Copper Pipe

Copper pipes are very useful in containing water, refrigerants or air. Hence, they are very commonly used in transporting these materials in various appliances in the house. However, for bending a copper pipe, one has to join two pipes at right angles with a fitting. This can be done by soldering copper pipes to each end of a fitting, at the point where the pipe has to bend.

What is Soldering?

Soldering works by capillary action. When the pipe and the fitting are heated, the soldering material is touched to the joint. The heat melts the soldering material, and by capillary action the material is sucked into the joint sealing it. Once the soldering material cools, an air-tight joint is formed, thus sealing the copper pipes and the fitting tightly together. It is important that the soldering material has a lower melting point than copper. Otherwise during the heating of the pipes up to the melting point of the soldering material, the metal pipes may melt.

Steps for Soldering Copper Pipes

1. Cutting the Pipe: Cut the pipe of required length. As copper is a soft metal, it can be cut neatly using a tube cutter. However, in case of larger pipes, a hacksaw may be used. If you are using a hacksaw, then ensure that the all the burrs at the end of the pipe are filed. Otherwise the pipe may leak.
2. Cleaning the Pipe: Cleaning the pipe and the fittings, and making them rust-free is an important step for sweating a copper pipe (soldering). Sandpaper, emery cloth and steel wool would be good for cleaning the outer surface of the pipe. However, to clean the inner surface of the pipe and the fitting, cleaning brushes would be more effective. These brushes are available in various sizes. Cleaning brushes that suit the copper pipe sizes and those of the fittings can easily be bought from the market. Apply a liberal coat of flux to the inside of the fitting and the outer side of the pipe. Place the fitting on the end of the pipe and move the pipe or the fitting back and forth so that the flux spreads evenly over the surfaces. Fluxing the objects ensures that even the minutest trace of tarnish is removed. Moreover, it reacts slightly with the molten solder and removes impurities from it. This helps the solder to flow freely into the joint.
3. Heat: Put the pipe into the fitting. Now you are ready for soldering the pipe. The heating equipment to be used depends upon the copper pipe dimensions. If you are using small pipes, then using a propane torch would be enough. However, for larger pipes, one should use a plumber's acetylene torch. As copper is an excellent conductor of heat, therefore heating the fitting at a single point or at a point on the pipe close to the joint would work. Hold the flame there for sometime so that the temperature of the object that you are heating reaches the melting point of the soldering material. Although 10 - 20 seconds would be enough, larger pipes may take a little longer. Once you feel that the joint has reached the right temperature, touch the soldering wire at the joint. If it melts, it means the joint has got heated to the correct temperature. Keep testing the temperature by touching the soldering wire to the joint. Once you have enough practice, you will get a hang of the correct temperature easily.
4. Soldering: Touch the solder wire to the joint once you are sure it has reached the soldering temperature. The solder will melt and be pulled into the joint between the pipe and the fitting through capillary action. In case the pipe is small, there is no need to move the soldering wire all along the circumference of the joint. As the solder melts, it will be drawn into the joint along its entire circumference. Once the molten solder starts pouring out, it indicates that there is no more need of the soldering material to fix the joint. Be careful so that not too much of the soldering material melts and accumulates inside the joint, as it will form bumps that will hinder water flow through the pipe.
5. Wiping the Joint: Once the pipe has cooled down a little, take an old rag, fold it a few times so that it is thick enough to protect your finger from the hot metal. You could also moisten it a little bit. Now quickly wipe the excess solder and flux away from the joint to ensure that there is no blobs of solder and flux. Nothing looks better than a bright clean shiny joint with a band of silver gray at the joint. In case you are using a wet rug, it may cool the pipe quickly, leading to the formation of blobs of soldering material at the joint. If that is the case, reheat the joint to remelt and wipe off the excess solder and flux.

Precautions to be Taken

• Always wear safety glasses while soldering.
• Never solder directly overhead.
• Wear a glove while applying the flux as the chemical may damage the skin.
• Use a heat shield if you have combustible substances close to the soldering area.
• Keep a fire extinguisher close by.

Soldering is a simple plumbing process that can be carried out at home. Once you master this technique, you can tackle a number of other domestic repair work.