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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?

  • also be aware the torch head makes a huge difference. I was using a $15 basic click start head and it would take a minute to get a pipe hot enough to solder. It was difficult on pipes mounted in place. I switched to a nicer torch (TS4000) and it gets the pipe hot enough to solder in seconds. – rpmerf Jun 6 '16 at 13:23
  • I have no idea what kind of solder was in that joint but even mapp gas wouldn't melt it. I ended up just cutting that leg off and re-doing a small portion of it. – mreff555 Jun 6 '16 at 13:28
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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.

  • I'm still not buying the complete burn with MAPP, but then again I haven't used it in 10 years or so. If it's just LPG and propylene now, I guess that makes sense. Thanks for the advice. – mreff555 Jun 4 '16 at 19:19
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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.

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There are all different types, sizes, and styles from many different manufacturers. This is just one example.

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i would say that regular propane gas,use flux,heat it evenly and the solder wil get to meltin and flow i have used it before and just make sure you stuff some light bread in the pipe to keep the water from dripping,since you already have the mapp dont get it to hot keep the flame a distance

  • And be careful not to toast the bread inside the pipe. :-) – Michael Karas Jun 4 '16 at 15:40
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    ... surely you didn't mean "bread"? Sealing food into a water pipe seems like a many-splendored bad idea. – Daniel Griscom Jun 4 '16 at 18:49
  • @Daniel Yes. thats what recommended, its melting in the water thereafter – aofkj Jun 7 '16 at 16:16
  • @aofkj Boy, I hope that if my plumber does this he never tells me about it... – Daniel Griscom Jun 7 '16 at 17:38
  • @Daniel As long as your shower is still working you shouldn't be worried even if he tells it to you:-) – aofkj Jun 7 '16 at 21:15

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