How to Solder Copper Plumbing

Soldering (otherwise known as sweating) copper pipes may look like a complicated and intimidating process, but with a bit of guidance and practice, it is a skill well within the abilities of the average homeowner. With some basic plumbing skills, small problems can be fixed without having to call a plumber, saving both time and money.

Before tackling “real” plumbing, it is always a good idea to practice on scrap pipes. Any older 1/2 inch diameter copper pipe will do, as long as it isn’t bent or heavily painted. If you can’t find old scraps of pipe to use, most home improvement stores sell shorter, inexpensive lengths of pipe you can use. You will also need the following, which can be found in the plumbing section of any hardware store:

* 1/2 inch copper fittings (T’s and 90 degree elbows are common, inexpensive fittings to practice with.)

* Propane blowtorch (often handily available in a kit with solder and flux.)

* Lead-free solder (nearly all available solder is now lead-free, but check the label to be sure.) Avoid solder labeled “acid core” or “rosin core;” these are meant for applications like electronics. For plumbing, choose a thicker width of solder (something that looks more like a lollipop stick than a single strand of angel hair pasta.)

* Pipe cutter

* Wire brush for cleaning the inside of 1/2 inch fittings. This will look like a miniature bottle brush.

* Fine steel wool or plumber’s “cloth” (sandpaper with a fabric back) for cleaning the outside of pipes.

* Flux (usually found right next to the solder on the store shelf.)

* Flux brushes

* An old rag for wiping off the joints.

* Safety glasses (never a bad idea, despite the fact that plumbers don’t wear them.)

* Work gloves for handling hot pipes.

* A vise (or a helper with heavy work gloves and potholders…the pipe will be HOT) to hold your practice pipe while you solder the other end.

* Lighter or other source of ignition for the torch.

Now that you have assembled all your materials, you are ready to start practicing. Use the pipe cutter to cut off a section of pipe that is about 2 feet long. Proper preparation of your pipe and fitting is essential to getting a good bond, so make sure not to rush the following steps.


1. Clean out the inside of your pipe fitting with the wire brush. Make sure there is no debris or burrs inside the fitting.

2. Clean the outside of the pipe with the steel wool or sanding cloth, making sure that the cleaned section is slightly more than will actually be inserted into the fitting. The cleaner your pipe and fitting are, the easier they will be to solder correctly. The copper should be bright and shiny, with no dull discolorations visible.

3. Using the flux brush, apply a small amount of flux to BOTH the outside of the pipe and the inside of the fitting. The flux helps clean off any impurities and helps the solder adhere to the copper. You want just enough flux to coat the pipe and fitting; wipe off any globs with a rag.

4. Dry fit the two pieces together. Make sure the pipe slides all the way into the fitting, and clamp the pipe in a vise (or have your well-gloved helper standing by to hold the pipe.


1. Keeping the propane cylinder upright, carefully screw on the brass nozzle, checking first to make sure the valve is closed.

2. Open the valve slowly, until you hear a slight hiss. Put your lighter in front of the nozzle and light the gas.

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3. Now that your torch is lit, adjust the valve until you have the right sized flame: about 2 inches long with a good amount of blue in the center. If your flame is too small, it will take longer to solder your joint. If it is too big, you run the risk of overheating the metal. (Larger flames are useful if you need to solder larger, heavier pipe.)

4. Hold the flame on the thickest part of the joint you are trying to solder (usually the fitting.) Don’t worry about heating the pipe; if you heat the fitting, the pipe will also get plenty hot. Hold the flame on the fitting until the flux starts to bubble out of the joint.

5. Touch the end of the solder to the joint. Don’t put the flame on the solder itself…if the joint is hot enough, the solder will easily flow and the joint will suck it in. If the solder doesn’t flow, continue to heat the fitting. If the fitting starts to turn orange and red, but the solder still doesn’t flow in, the joint is probably not cleaned or fluxed properly. Let it cool and start again.

6. You may need to heat the opposite side of the fitting to make sure solder has made it all the way around. (This is more of a concern with larger pipe sizes, or if you are trying to heat a inch pipe with a very small flame.)

7. Once you believe the joint is soldered, remove the flame from the pipe and (quickly AND carefully) wipe off any excess solder with a dry rag. This will not only make your joint look neater, but will help you see any potential gaps.

8. Turn off your torch.

9. Let the pipe cool and inspect it. Clean the joint with steel wool to see the joint better, and look inside the fitting to see if you can spot solder coming out at the end of the pipe. There should be some solder visible inside the fitting; if you have globs of it, however, you are using too much solder.


1. If you are replacing a section of copper pipe, be sure to buy the right type of pipe. The two most common types of copper pipe are M and L. Type “M” pipe is cheaper and thinner walled, and may not meet plumbing codes. Type “L” pipe is heavier, stronger, and will last longer, and is required by code in many areas of the country.

2. Before cutting into existing pipes, make sure you have turned off your main water supply and drained the lines. If you can’t drain the lines effectively, have a bucket handy to catch the extra water as you cut into the pipe.

3. Pipes are nearly impossible to solder if they have water inside them. If you are trying to fix a leaky joint, make sure the pipe is emptied of water first.

4. If you are using a brand new propane tank, keep in mind that the high pressure in the tank may make the flame initially slow to shut off. If you turn the valve off, don’t be alarmed if the flame does not immediately extinguish, and don’t try to crank the valve extra hard or set the still-lit torch down on the ground.

5. If you need to solder a pipe that is close to joists or walls, use a piece of flashing behind the pipe to keep from scorching your house. If you are particularly nervous about setting your house on fire, you can even use a spray bottle to wet down the joist or wall. The real plumbers may laugh at you, but you’ll feel better.

6. While soldering pipe, keep in mind that small globs of solder are likely to fall while you work. These globs are molten metal, so do not stand directly underneath anything you are soldering. It is also a good idea to wear jeans and sturdy shoes to protect your legs. Put down an old towel or sheet to protect your floor.

7. If you plan on doing anything more than fixing a leaky joint, it is always a good idea to familiarize yourself with some basic plumbing code. If you are going to do something, you might as well do it right, and plumbing repairs often offer a good opportunity to fix previously installed code violations.

8. If you are planning a major project, like the installation of a new bath, it is always a good idea to meet with your local plumbing inspector. He or she can help you with the planning of your project, as well as offer advice on issues you may face and how to resolve them.

With some basic plumbing skills under your belt, you can now rest easy, knowing that you can handle minor plumbing emergencies all by yourself.

Inland Cal Plumbing

7168 Archibald Ave
Rancho Cucamonga, CA 91701