This is the MacGyver special. Grab a length of strong twine or even unflavored dental floss (mint works, but the residue is weird). Tie it around the pipe, then pull back and forth like you’re starting a fire in a survival movie. The friction generates heat, which melts—yes, melts—the copper locally because of its high thermal conductivity.
After about a minute of vigorous sawing, the string will get hot enough to cut through. You’ll smell a faint, coppery burning odor, which is your brain going, “Is this normal?” It is. Pop the pipe in cold water to cool it, then snap it clean. Surprising fact: this method was used by ancient Roman plumbers, who had no internet and still managed to build aqueducts that worked. Meanwhile, I can’t find my car keys.
