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?
Plumbing – soldering pipe with mapp gas
plumbingsoldering
Related Solutions
You might have luck using two brazing torches, like these. My concerns usually aren't about making a mess; it's getting it to work without burning holes in it and physically getting it back together after a de-solder. I'd start over, but it's worth a shot on a $20 fitting. I'd say my re-solder success rate is 50\50 without doing more work than just using new, clean fittings. I've never done 3" and I wouldn't without a wrap-around torch head for an acetylene kit.
These brazing heads really are nice and make quick work out of plan old soldering.
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My guess is either the joint wasn't cleaned enough and/or not fluxed properly. I have had problems when my old tub of flux got dirt in it. When heating, the dirt burned and ruined the flux preventing a good solder joint. Check your flux and flux brush for dirt and replace or clean as needed. Then clean all of your joints thoroughly with one of those wire brush cleaners for copper tube or scotch bright.
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Best Answer
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.