Watch this video from This Old House to learn how to solder copper pipes.
1 Use emery cloth to clean outside of copper tubing.
2 Clean inside of fitting with wire brush.
3 Apply flux to pipe and fitting with acid brush.
4 Slip fitting over pipe.
5 Heat fitting with propane torch until flux bubbles.
6 Apply solder to fill joint; wipe off excess solder with rag.
7 For an easier way to sweat joints, use pre-soldered fittings, which require the application of heat only.
8 For a no-solder flared connection, use flaring tool to deform end of copper tubing.
9 Slide nut onto tubing, then tighten flared connection using two wrenches.
10 For a no-solder compression fitting, slide brass ferrule onto pipe, add nut and tighten fitting to join two pipes together.
11 Copper fittings lined with neoprene gaskets permit pipe connections without special tools, wrenches or a propane torch.