How to solder copper pipes – a straightforward explanation.
The first step is making sure the pipe(s) to be soldered are clean and dry. Water will cause problems, so make sure the area is dry.
Once the area in clean and dry, apply flux to the pipe end you're starting with. This generally has the consistency of vaseline, and doesn't take much.
After the area has been coated, slide the sleeve (a joining peice) onto the pipe, and hold it in place (Vise grips work well, but they DO conduct heat, so be careful, and don't hold it too tightly)
Heat the pipe with the torch close to the sleeve until your solder melts on contact. This is the part that takes practice. You want it hot enough to melt the solder easily, but not too hot. Once you've done it a few times, you'll get a feeel for how hot that is...
Once the solder is melting on contact, touch the solder to the pipe at the seam where it meets the sleeve. Something called 'capilliary action' will pull the melted solder into the space between the pipes, unless you've got it too hot. This process shouldn't take more than a few seconds.
if you're working on a pipe that has water in it, and you just can't get it all out, this will still work, but be careful for the steam you'll create. It's hot, and will burn you.