Soldering Copper Pipe

Soldering copper pipe is a basic skill for many DIY plumbing projects. Over the years I've seen all kinds of solder joints. So when someone tells me they tried and failed at soldering copper pipe I know what it looks like. It's usually a scorched and blackened fitting with discolored pipe on either side, and way-too-much solder in and around the joint.

This article isn't about the basic steps of cutting, cleaning and reaming your copper pipe. This info is available everywhere! More useful to you is learning soldering tips that are difficult or impossible to find. These few tips should make the difference, allowing you to succeed at soldering copper pipe and dispelling the myth that soldering pipe joints requires some special skill that is beyond the DIY plumbing layman.

I learned techniques for silver soldering copper pipe joints before I learned to sweat joints so it has always seemed easy to me. I'm confident that I can make it seem easy for you too with just a little coaching.

I have developed all manner of “tricks” to solve various plumbing problems, but there is no trick to soldering copper joints. All that you need is the right torch, flux, and solder. Put those elements together and you can do it. Some practice on top of that and you will do it confidently.


The Right Torch

The torch I recommend is the “TurboTorch” by Thermodyne. It's the only one on my plumbing truck! The common household propane torch has a cone-shaped flame, and while I could solder with it, I'd rather not have to. It is the shape of the flame more than anything else I am concerned with. Soldering pipe joints requires a "rose bud" shaped flame that will wrap around the joint heating a wider surface than a pencil point shaped flame could in any but the most experienced hands. I set my flame only as large as is needed to wrap around the joint and hold the torch so that the flame reaches the joint at about a forty five degree angle, shallower if there is anything near the work I would rather not heat or scorch.

Got Gas?

Many pros use "Mapp Gas" (it's a combination of propane and acetoline gas) for soldering copper pipe. I'm content to use bottled liquid propane. LP takes a little longer but I am not in a hurry. You shouldn't be either! Mapp gas is hotter, allowing the work to go faster and also allowing the flux to scorch more readily. Watch the color of the flame, hold the work in the blue of the rose bud, not the pale blue at the root of the flame.

The Right Flux

Solder will not cohere to copper pipe unless the copper has been chemically treated to receive it. This is what the flux does. There are many types of flux for many types of work, but to sweat joints in a potable (safe to drink) water system you must use a water base flux intended for potable use.

The only other important criteria in selecting a flux is the scorching temperature. The scorching of flux, which is the point at which it becomes a dark solid mass in the joint, is the chief reason for failed joints at the layman level.

Solder will not penetrate a joint that is scorched. It won't even adhere to the outside of it. This is the reason I recommend lower flames and slower work. Taking too long won't scorch flux, but too much heat will.

I've used many brands over the years. Since the change to water-soluble flux, none has pleased me as much as ”Everflux”. You shouldn't let it dry out. If it gets dried out, just dampen it again before you use it.

The Best Solder Is Safe Solder

I come from the good old (bad old) days when plumbing was sweated with “50/50” plumbing solder. It was 50% lead and 50% tin. When we lost that plumbing solder because of public health and safety-oriented plumbing code changes, we all had to relearn soldering copper pipe.

The new lead-free 95/5 solder, 95% tin 5% antimony, has a lower viscosity than 50/50. That means it flows more quickly when molten. It flows so quickly that it can flow right through the joint while it is being applied leaving a gap at the top of the joint.

As with other changes in our industry we soon adapted to the higher skill level needed to perform the job. (We had to!) Using the right plumbing solder made a big difference. My choice is “Silvabrite” solder.

Silvabrite 100 is composed of 95.6% tin-4% copper-and .4% silver. It costs more, but it gives you a nice thick and smooth-working solder that is very reliable. Best of all, it only requires the “old school” skill level to apply. That makes it an excellent plumbing solder for those who don't wake up with a torch in their hand.

I am a full time pro and I can solder with whatever you give me, but all I buy is Silvabrite. Leaks slow your progress, do damage on the job, and make you look bad. I don't mind a little extra expense to ensure I never have these problems.

Once you've gathered the tools and materials, click here to learn how to solder copper pipe.

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