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How to Solder a Pipe & Fix Water Lines

Learn how to solder a pipe and fix water lines from Master Plumber John Wood in this plumbing repair video from Howcast.


Okay. Let's talk about fixing water lines. Depending on what region of the country you're in, you may see PEX tubing, which is a type of plastic or something, but in the five boroughs of New York City it is exclusively copper. If it's not, you're not legal. So this is what we call half-inch, indicating the size of the pipe, half-inch type L. L is the indicator of whether you can use it for potable water, potable being clean, domestic drinking water, showering water. Okay. This is what you see throughout the city, under your sinks, everything else. This is a fairly thick-walled copper pipe, and it's easy to repair unless you have something bad happen.

But generally speaking it's easy to repair. Now for the purpose of this video I'm going to show you how to solder a 90, okay, also known as an L, which is a very small fitting. This would be, for example, let's say we installed a new vanity or a kitchen cabinet. You'd have a raw copper pipe coming out like so. All right. And then you'd need to put a joint in there of some sort. It might be an L going up like so and then a valve that would shut off the supply to your sink. Okay. So for this purpose I'm just going to solder this 90. I'm going to show you how to properly do it. Ask any plumber how to solder, and you'll get any number of different stories on how to do so. This is is how I solder, not necessarily saying it's the Bible way to solder, but this is how I do it, and it's worked for me for 20 years as a Master Plumber. You need a few things. An emery cloth, this is basically sandpaper, but it's a strip. You need a fitting brush. This is a half-inch fitting brush. You need silver solder. Be careful not to get lead. It says very clearly 95 percent/5 percent. And your trusty torch.

So we start by cleaning the joints to be soldered. Okay. In this case we're going to use these two pieces of pipe. You just kind of wrap it around, and you're going to clean it. Be judicious with the cleaning. Okay. I don't want to see any black marks on that recently sanded pipe. That's carbon. That will cause a leak. That's another reason I'm wearing gloves. People might call me a primadonna for doing so, but it actually keeps the oils in your hands off of the joint. This is not conducive to soldering. The oils in your hands are not conducive to soldering. So now we're going to take our fitting and our fitting brush, okay, just a wire brush. This one's kind of beat up, but it will still get the job done. Again same idea, you twist it around in there until you can see your reflection. So we've got a nice, clean 90-degree elbow. The next thing you want to do, again the gloves come in, they're very imperative here.

No oils from your fingers going onto these joints. The only thing you want on these joints is acid paste, otherwise known as flux. Okay. The purpose of this, and you don't have to be too liberal. This is called an acid brush. The purpose of flux in general is when you heat the pipe to pull the silver solder into the joint. Okay. Don't ask the physics on how that works. That's just how it works. So I generally start with the fitting first. And you just need a film of it, just a little film. You don't need to paint a Picasso doing this here. So we've got the joint fluxed. We just kind of pass around the edge. Okay. We're doing a half-inch joint, so really all you need is a half-inch of flux. Okay. We don't need a ton, a big, messy, ugly pasty joint. And this stuff is all that great to get on your hands, too. We've fluxed everything now. I've got my joint together. This could be an offset in a wall. It could be anything. For any reason I could be doing this.

So now I'm ready to apply heat and actually solder the joint. Again when you're using a torch, always have the fire extinguisher handy, especially if you're not a professional. Yes, I know how to use the torch better than most people that do not use it every day, but I still have a fire extinguisher right over within five feet of me. Okay. So keeping in mind now when we activate the flame on this, we don't need to blast it with as much flame as we can possibly get. There is a regulator right here that I can adjust that flame. This is an excessive flame for half-inch. It's too much heat. It will heat up too fast, and you'll see the joint actually smoke. That's not necessary. I'm only soldering half-inch. This would be a more appropriate flame for three-quarter or one-inch or something like that. So I'm going to turn this down. You can hear it. Now I've got my silver solder. One of my little quirks, I like to actually drag the emery cloth along the edge of the solder to make sure that there's no impurities in that solder. Okay. And then I like control over the solder, my finger applying just a little bit of weight to it. Okay. I'm going to put a little curl to it, and the rule of thumb is if you're doing a half-inch joint, you need about a half-inch of solder. That's all you need. Okay. So the solder itself when it liquifies will follow the heat. It will follow the flame. So where do I want to apply my flame? I want to apply my flame to where I want my solder to be, which in this case is inside this joint. We would take our torch, heat from underneath if you can. It's not always this easy inside a wall or something like that. I'm going to slide it down to the pipe a bit. You're going to see that flux start to bubble. Okay. Now if you're not sure whether you've reached temperature yet, you can do what I call a pass-by. Just give it a little touch. And we're at temperature. Run it, and you can see the solder sucked right into the joint. And you get a little touch under there. And that's soldered.

Repeat on the same side. Another common mistake that newbies make is they are hurrying and they forget to solder one side of the 90, which is a real bummer because it's just a silly mistake. And around we go, and we're done. That's it. No more. No more heat. Back the heat off. Leave the joint alone. You see so many guys going in there and bashing at it with flux and wiping it with a rag. The joint is still cooling. Okay. What you risk doing there is moving a pipe because it's partially liquid. You're moving a pipe that you just soldered, and now you've got what we call a cold-soldered joint and again, a leak. I like to hit it with flux, because it's still hot enough that the flux will kind of boil off some discoloration there. This is purely aesthetic. You just kind of hit is like so. You see it sizzling. I would have a soldering rag or a little piece of paper towel or anything like that, and you just kind of wipe that joint nice and clean. On the same note here, I don't like dropping this into a bucket of cold water. Why? Because it stresses the fitting. It stresses the seam of the fitting. Just leave it alone. Let it cool naturally. Have some patience. And you've got a nice, tight copper joint there.

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