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How To Desolder

How To Desolder

A plumbing expert demonstrates how to desolder pipe fittings, a process that uses heat to melt the solder and break apart the pipe no matter for how long it has been joint.

Occasionally, you need to remove a joint that's already been soldered. We call that process desoldering. Sometimes, it will be that you need to get into the pipe work or it may be that you need to take a straight coupling out to put a T piece in.

The process is very straightforward because we use heat to melt the solder, once the solder's molten, it releases its grip. So, consequently, where we've used heat to make the joint in the first place, we can use the heat to take the joint apart. Slightly different from when you're soldering, in that, with this, you tend to set the torch up so the torch is held and you can use both hands.

What we're going to do is turn the torch on, play the heat onto the joint and we're going to use a certain amount of sideways pressure on the tube. I'm going to be flexing it so I can tell when the solder is molten. I need to be aware of the fact that the solder melts at 400 degrees, the torch is putting out 1000 degrees.

It's very easy, if I leave the torch in too long to go past the point where the solder is molten and start actually changing the temper of the metal, starting to make it soft copper. So, I'll put it into the heat and then take it out. All the time, I have some movement and then maybe put it back if I need to.

So, let's light the torch, take it in and I'm going to choose the hottest part of the flame which is that light blue, where that light blue cone ends. The light blue cone is unburned gas. So, I bring the joint in, give it a few minutes, I can see that rainbow effect, where it's starting to change colour.

I'm going to take it out of the heat, I don't want it to get any hotter, and just by flexing the pipe, as the solder is now molten, you can see that the joint can come apart. I'll need to give that a little bit of a tidy-up just to get that out. But you can see that we have a layer of solder right the way around the pipe.

That's because, although we started off copper and we added tin and zinc, what has actually happened is there has been a chemical reaction. We tend to think in terms of soldering and these sort of processes as if they were glue, as if we were sticking things. In actual fact, we are changing the chemical properties and these are all chemical reactions.

The flame is a chemical reaction, the soldering process is a chemical reaction as well. So, this is called tinning, it's where the tin has reacted with the copper and has actually formed a new alloy. I can remove this because solder's quite a soft metal.

I can file that off, but if I'm going to be applying a new fitting, then it's just as easy to put a new layer of flux on, put the new fitting on and solder as if I was acting from scratch. So, desoldering is a process that we use a lot. It gives us the opportunity to take joints apart that had previously been together and it doesn't matter whether that's a fresh joint or it's been there for 200 years.

It will still be the same process, you melt the solder, the joint can come apart. So, a very useful technique for altering pipe work or for taking sections out or for repairing them, and that's how we desolder pipe work.
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