Soldering Copper

For a good solder joint, all connections must be clean. There can be no dirt, grease, or coating on the copper. The outside of the pipe and the inside of the fitting should be sanded or wire-brushed and then apply a healthy coat of flux. The flux will help the solder bond to the copper.

Another thing that will keep you from soldering is water in the pipe. There can be NO water! Believe it or not, a few drops of water can keep you from getting the fittings hot enough to melt the solder. If you are having water slowly drip down a pipe, try this old trick. Stuff some bread up the pipe to create a plug. It's best to use the white doughy stuff but any soft bread will do. Stuff it up there (that's what I'm doing in this photo) and it will keep the water from dripping long enough for you to solder. Later, the bread will disolve and the water will flow just like normal.

How Soldering Works

Soldering a fitting uses two principles, heat and wicking action. You apply heat to one side of the fitting (avoid applying heat directly to a joint) and then start touching the solder to the opposite side. Once the fitting is sufficiently hot all around, the solder will melt into the joint and a wicking action will bring it around to the heat source. The heat you're applying on one side actually wicks the solder to it, so applying the solder on the opposite side ensures equal distribution. Any gaps in the solder will mean a leak.