If you saw my last Instructable on making Motorcycle Saddle Bags out of 40MM Ammo Cans
there was a step in which we sprayed down the cans with paint stripper and then rinse them with the hose. Well, if you've ever watched somebody walk off with a garden hose that hasn't been secured to anything other than the faucet itself, you know what's about to happen especially if that faucet is sticking way out. Some copper is about to get mangled. Secure your hoses between you and the faucet. Then maybe you won't ever need this bread trick.
In this case I noticed a pretty good twist in the pipe right against the wall and a small crack that was leaking water, and this is right above my main. There are other Instructables on patching pipes, making the cuts, and sweating so I'll move fast through those parts. I'm not trying to compete with those and they are excellent, I'm just showing a trick for doing it when leaky. So I punched out a bit of wall and cut out the bad section with a pipe cutter. Use a pipe cutter, as much fun as power tools are, they and copper piping do not go well together... you will not get straight cuts and straight cuts are crucial to prevent leaks. Most copper pipe cutters cost less than 10 bucks. I bought one today for 8.50 after realizing what a disaster my grinders metal cut off wheel was making. Use standard sweating techniques to put a new pipe section in and the couplers needed, right up until the last bit which never quite quit leaking. I tried for about 5 minutes to sweat this piece on before realizing it would be impossible and remembered this trick my old boss taught when I was a kid working a summer job.