How To Solder Copper

Soldering copper, also known as sweating copper, is an old art and an easy one to learn. Copper piping is widely being supplanted by new technologies such as pvc, cpvc, pex tubing, and cross-linked pex. But there are still situations where copper water piping is desirable and even widely used. You will still typically find copper water pipes in commercial buildings such as schools, hospitals, public buildings, and business and industry. Some contractors still utilize copper water piping in residences in certain parts of the country. Copper water piping, unlike other materials, adds to the value of your home. So, where you own an old fixer-upper, a finely finished Victorian, a brand new home, or anything in between, if you hope to maintain your property, you will most likely want to know how to solder copper.

Preparation

1. Clean the end of the pipe and fitting. You can use sandpaper, emery cloth, or even coarse steel wool to clean the pipe at least the depth of the fitting socket. Clean the fitting socket, as well, with the proper size fitting brush found in most hardware stores.
2. Apply a good quality flux to the end of the pipe and to the inside of the fitting socket. Go easy in the fitting because a heavy amount of flux in the socket will cause it to boil out, splutter, and possibly burn you. Do apply a generous layer to the end of the pipe. Avoid using the types of flux that are “self-soldering” or that contain lead. Don’t worry about getting your fingers in the flux after it’s applied. That’s the source of an old wive’s tale.
3. Insert the end of the pipe into the fitting socket and twist it as you push it all the way in. You may feel some resistance but it should go in easily.

Tools needed to solder copper pipe and fittings

Solder the Joint

1. Light your torch and hold the tip of the flame at the base of the fitting socket (the end farthest away from the pipe). Play the flame back and forth gently instead of holding it in one place.
2. Use a good quality lead-free solder. Use 95-5 solder for a good, strong joint that will even last underground.
3. Touch the tip of the solder to the joint where the pipe meets the edge of the fitting opposite of where you are holding the torch tip unless you are soldering larger diameters of pipe.
4. When the metal reaches the proper melting point, the solder will rapidly flow around the joint and inside it. Watch the joint itself and when the solder flows in the manner described, remove the solder and the torch and wait for the joint to cool completely before moving it.
5. After the joint has cooled, you can wipe the excess flux residue away with a damp cloth.

Tips

If you move the joint, even slightly, while trying to solder it, it will crack. If that happens, just apply a little more flux with a small brush, reheat the fitting, and apply more solder.

If you apply too much solder, it will simply run out of the joint and that is wasteful. Only feed solder until you see it flow around the circumference of the joint and then remove the solder.

If you wipe the joint with a wet rag, it will make the copper bright and clean. However, there is a chance that the sudden coldness will crack the joint so let it cool a bit before wiping it down.