I am trying to open up some solder joints on a 1/2" residential cold water line, and I am having trouble doing so. I am using a propane torch, and I confirmed that the pipe was evacuated. My brother says that some plumbers use solder with a higher melting point and MAPP gas. Is this true? The concept of this seems like a bad idea for so many reasons and I'm concerned about burning a hole in my pipe. I also don't like the idea of using a much dirtier gas indoors. Is MAPP gas the way to go, or should I try something else?
If it is copper pipe and was indeed soldered (using a tin-lead alloy or a more modern lead-free solder), then propane should work okay. However, MAPP (originally methylacetylene-propadiene propane but now stabilized liquefied petroleum gas with propylene) will heat faster and, with a common sense caution, not melt the pipe. That is, don't heat the pipe until it is yellow hot; red or orange is fine.
If the pipe was brazed with silver solder, which is common in HVAC systems, propane is not enough: you have to use MAPP to get it hot enough to work.
Propane and MAPP both burn completely. You need not worry about the exhaust: in all cases the result is water vapor and carbon dioxide. Just like when animals exhale.
MAPP gas is the way to go. It burns hotter, so It will heat the pipe faster. It will even heat the pipe if there's a bit of water in the line, something that propane will not do.
If you're worried about burning surrounding materials, you can use a heat shield.
There are all different types, sizes, and styles from many different manufacturers. This is just one example.
Contrary to a good friend's advice, who was a plumber, I've several times used oxy-acetyline (as in car body welding, etc.) even on pipes still containing water,and as long as I wait until the solder melts, that's as long as the heat needs to be there. MAPP seems to be close to that, so should do the job. But - I've been welding for many decades.