Soldering Copper Pipe With Flux. Be careful to clean and flux the end of every pipe and the inside of the fittings before assembling them. The main thing is to choose the right kind of flux and solder.
Solder will not cohere to copper pipe unless the copper has been chemically treated to receive it. Besides you need to know how to prepare the pipe and the fitting before you solder them together. Soldering a copper pipe is just like soldering any two metals.
The amount of heat needing to be applied will vary but well deal with that in the next step.
When flux heats up it will begin to bubble or sweat. It is used in covering the cleaned copper surfaces to be soldered before heating and assembly. Soldering one joint at a time is inefficient. Soldering copper pipe requires a relatively large amount of high intensity heat which is why a propane torch is typically used to heat the joint.