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How To Solder Copper Pipes Like A Pro - Plumb University

How To Solder Copper Pipes Like A Pro

by Trevor Woods | Last Updated: April 2, 2020

Copper pipes are used all throughout your home. Drainage lines, water supply lines, and even venting piping. And after a while, these copper pipes are bound to show signs of wear and tear. Knowing how to solder copper pipes will allow you to repair leaky joints, worn sections, burst pipes, pinhole leaks, or add on and renovate your plumbing system.

Soldering (also called sweating) copper with an open flame may seem intimidating but fear not! You can do this yourself without resorting to calling a professional for help. With our guide, we will take you from beginner to soldering pro in no time! All you need to do is follow a couple of basic instructions and you are good to go. 

With a little practice, you will have mastered the simple skills required to solder all types and sizes of copper pipe. Following the simple steps in our tutorial, you will learn how to identify copper tubing, cut pipe, clean and flux fittings, and how to sweat copper plumbing without leaks.

Our comprehensive guide will teach you all the best tips and techniques to solder by yourself and avoid making mistakes and turn you into a copper pipe soldering master!

Copper Pipe and Fittings

Copper is a soft, malleable, and ductile chemical element Cu with very high thermal conductivity. These attributes make it the ideal medium for soldering as it allows the transfer of heat required to melt the solid solder and have it flow and fill joints.

In addition to sweating, this perfect plumbing material that can also be brazed, bent, flared, roll grooved, and manually extruded to suit any plumbing need or system.

Natural antibacterial properties destroy a wide range of microorganisms and copper tubing in plumbing systems suppresses Legionnaires’ disease. Thie makes copper one of the safest and healthiest plumbing materials to use in your home.

Copper does not react with water and rust like piping made with iron. But it does react with air and will oxidize forming a layer of green verdigris that will protect the underlying material from further corrosion. If a copper pipe is in contact with other metals like stainless steel or galvanized metal it will deteriorate due to galvanic corrosion.

Water erosion and galvanic corrosion are the most common causes of plumbing leaks at joints and piping connections to pipe fittings that you will find in your home.

Copper Pipe Types

Not all copper pipes are made the same. Copper tubing comes in a variety of pipe wall thicknesses. The four most common types of copper pipe found in your home are types: K, L, M, and DWV.

Each letter code will be printed on the side of the pipe and is color-coded to help identify it. Type K copper tube is green, type L is blue, type M is red, and DWV is yellow. These markings will identify the relative thickness of the pipe and what type of plumbing system it is used for.

Uses of Copper Pipe Types

The various types of copper pipes are utilized in a variety of ways; from medical gas lines found in hospitals to irrigation and solar systems, heating and air conditioning, even compressed gas and vacuum lines. There isn’t much this pipe ain’t good for!

All copper pipe types are suitable for plumbing in your home but not every type is designed to match each plumbing system. Water supply lines and drainage pipes have their own requirements which means selecting the right type of copper pipe for the application.

DWV copper, for example is used exclusively for drains, wastes, and vents (hence the DWV acronym). DWV copper is not rated to handle the pressure of water or gas supply piping due to it’s thinner-walled construction. So it’s important to identify what type of copper you are repairing and match it accordingly.

Type K or green copper pipe is suitable for burying underground is typically found on the water main entering your home. Types M and L will make up the majority of your water supply piping so we will focus on these two kinds of pipe to solder on but the same principles apply to all types of copper pipe.

What’s The Difference Between Type M and L?

The biggest difference between between type M and type L copper is the pipe thickness. Type L copper has a thicker pipe walls and therefore has a higher pressure rating. This increased pressure rating and weight means the pipe requires more copper to be manufactured is reflected in the price tag.

Don’t let pipe wall thickness confuse you. Both Type L and Type M copper pipe have the same outside diameter and used the same fittings.

So Which Type Of Copper Should I Use?

Both Type L and M are suitable for indoor water supply lines. Each are rated well above the standard water pressures you will find in your home. Unless your local plumbing code states otherwise, either is acceptable.

So it really comes down to cost. For smaller repairs, you probably won’t notice much of a price difference but for larger jobs Type L copper will be noticeably more expensive. If you are on a budget Type M copper pipe is your best choice.

You do get what you pay for and many plumbers will opt for Type L copper because it is more durable and will last longer. This pipe is less prone to pinhole leaks and erosion over time.

If you really want to nerd out on copper plumbing, we recommend you check out the Copper Tube Handbook from copper.org. Now that you copper pipe aficionado, let’s get ready to do some soldering!

Tools And Materials Needed

Sweating copper pipe yourself can be quite economical and you are saving money on not having to call a plumber for help. All you need are the right soldering equipment and some materials!

Safety Equipment

Safety is always a concern when working with open flames and soldering torches. A few pieces of protective gear and you will be safe to solder. Make sure that you have a fire extinguisher, a bucket filled with water, or a water spray bottle nearby in case of a fire.

Keep in mind that the main household water supply is probably going to be turned off when you are working with the copper pipes, so make sure you have extra water close by.

Also, always shut your torch off whenever you put it down since the tall propane tank can be tippy. A lit torch could potentially fall over and could end up burning or scorching something.

Goggles or Safety Glasses

These will keep your eyes protected from molten solder and or splattering flux paste.

Heavy Gloves

The pipes and fittings you solder are going to get very hot so handle them with care. We recommend leather gloves to withstand the heat and they don’t melt like rubber or nitrile coated gloves.

Fire Protection Cloth

Take a steel plate or a flame protector cloth and cover any flammable materials, such as wood, before soldering. A fire protection cloth can be used to solder on or protect nearby surfaces if you are working in a confined space.

Fire Extinguisher

Just in case! You can borrow your home’s fire extinguisher if you want and it never hurts to have some water and damp rags handy to clean and cool you solder joints.

Hat And Long-Sleeve Shirt

Protect any exposed skin from burns and a hat is especially important for protection from molten solder drips when working overhead.


Measuring Tape

A tape measure is like a flexible ruler that you can use to measure you copper pipe and fittings. Find one with a locking tab and easy to read markings.

Deburring Tool

These are used to clean off any burrs or imperfections from cutting your pipe. You can also take your and use a file if you want.

Tube Cutter

These cutters are very important. You can use a hacksaw but cutting straight and square can be a challenge. Copper is a soft metal which makes using tubing cutters easy. These cutters make short work of copper pipe and tubing leaving you a perfect cut every time.

Make sure you buy the right kind for the job. Working in tight spots may require mini or close-quarters copper cutters. Cutters rated for up to 1″ pipe will allow you to work on the majority of all household water supply lines. Anything larger than 1″ is best done carefully with a hacksaw or bandsaw.

Emery Cloth

steel wool will also work.

Wire Brush

Wire brushes are used to clean the inside of plumbing fittings and are specific to the pipe size you are working with. It’s easiest to purchase a pipe cleaning tool for both 1/2” and 3/4” pipe and fittings.

You can use emery cloth or fine steel wool and your finger to clean the inside socket of copper and brass fittings but it can slow and tedious. Not mention how sore you fingers get after a while! Save yourself the pain and speed up your pipe cleaning process by investing a proper copper cleaning tool.

Soldering Torch

We strongly suggest you purchase a quality torch with a regulator and a built-in igniter. The regulator will allow you to control how big and hot your flame is and the lighter is more convenient than lighting the torch with a flint striker.

You can use a heat gun or flameless soldering tool but they heat up copper pipe very slowly and some may not have enough energy to solder larger diameter pipes.

Torch Fuel

You have a couple of options when it comes to selecting the fuel type for your soldering torch.

Propane is the standard fuel tank of choice. It is readily available and fairly inexpensive. You can even use 1 lbs propane bottles that are found on most camping lanterns and grills.

MAPP Gas has a higher burn temperature than propane and will have faster heat transfer. This extra heat can be quite handy if you have to solder a copper pipe with water in it and you have to boil the remaining water out of the pipe to complete your repair.

Stay away from Oxygen and Butane fuel tanks. Oxygen is not a suitable choice as it’s higher burn temperature is used for brazing and not soldering. And Butane does not burn hot enough and these torches are typically too small to solder copper pipe. Butane torches are meant for fine soldering jobs and won’t have the capabilities to solder copper pipe properly.


Copper Pipe

Match the diameter of pipe to the project you are working on. Most copper tube will be marked on the sides of the pipe walls identifying what size it is.

Copper Fittings

You can get a variety of copper fittings; elbows, couplings, tees, and caps to name a few.

Can You Solder Brass?

You can also use brass fittings depending on the application but they will typically be more expensive. You might find red or yellow brass fittings if you are soldering drainage lines or valves. The soldering process is the same as copper fittings but they typically require more heat to allow the solder to flow.

Solder Wire and Paste

Solder is a fusible alloy used to join less fusible metals. Copper melts at temperatures higher than 1981 degrees Fahrenheit where as plumbing solder will start to flow at 460 degrees Fahrenheit. So it’s much easier to bond copper pipe and fittings with solder.

You can find solder in bar-form but it is much easier to work with in wire form found in spools. Make sure that if you are working on copper water lines that you use lead-free solder that is safe for potable water. Leaded solder can leach into your water supply, not good!

Solder paste or flux is a cleaning, flowing, and purifying agent. When flux melts and turns to liquid under heat it facilitates wetting and prevents oxidation of the joint. Because flux wets the solder connection it promotes capillary action which allows the molten solder to flow into tiny spaces, even soldering vertically against gravity!

Tinning flux is also a great option as it has a little bit of solder already built-in.


Paper towels aren’t a good choice while working around flames but if that is all you have, keep them moist with a bit of water. It will quench the solder joint and prevent the paper towel from accidentally going up in flames.

Step By Step Guide On How To Solder Copper Pipes

Gather up your tool and get ready to solder. Sweating copper joints can be done easily with a few simple steps; measure, cut, ream, clean, flux, and add heat. Follow along and you will be soldering like a professional in no time!

A tube that has water in it cannot be soldered. You would need to drain your water lines and dry out the pipes in the places that are to be soldered. You can speed up the drying process by using the torch to heat the tube and evaporate any remaining water.

Also, water and air expand under heat. To prevent any build-up of pressure inside the tube, make sure that it can escape during the soldering process. The easiest way to do that is to open any nearby valves or turn on a faucet at one end of the line plumbing line. 

1. Measure

If you are soldering a copper pipe between two fittings, you will need to measure the distance between the fittings and add the depth of the fitting socket on each end. This cup depth will ensure that the pipe engages completely with each fitting cup.

You can typically round off to the nearest 1/8″. And you “dry fit” your pieces to make sure everything fits before they are sweat into place.

2. Cut

To make a perfect cut on copper pipe we recommend you use a tubing cutter. These cutters easily make straight and clean cuts every time. First, hold the pipe securely and place your pipe between the guide wheel and the cutting wheel. Line up the cutting wheel with where you want to make the cut and tighten down the handle until the cutter is squeezing the pipe firmly.

Next, rotate the tube cutter all the way around the pipe. This first rotation will score the copper and you should see a cutting mark around the circumference of the pipe.

After that, tighten the cutter’s knob about a quarter-turn then once again rotate the cutter, which is going to cut the pipe deeper. Keep a solid grip on the pipe to avoid and slippage while you are tightening and rotating the cutter. Continue this process of tightening then rotating the tube cutter until the copper pipe is cut completely and snaps off.

Slow And Steady

Make sure you do not tighten the tubing cutter too quickly because you might dent your pipe, causing you to start all over again.

If you are using a hacksaw for cutting larger copper tubing, like a kitchen sink drain line, make sure to cut square and perpendicular to the length of the pipe.

3. Ream 

The cut you just made might look clean but you need to remove the copper ridge made on the inside of the pipe by the force of the cutting wheel. If you don’t remove this inside lip you can restrict or create turbulent flow through the pipe.

Also, a pipe that is not reamed properly could end up reducing water your water pressure or increasing the rate of erosion and the possibility of spring leaks. When working on drainage pipes, ridges or burrs will catch debris and waste creating blockages and plugged drains.

Ream and clean the cut end in order to get rid of the inside burr. Insert your reaming tool then twist a full revolution. Feel the inside of the pipe with your finger to see if you notice any remainder of the burrs inside. Continue reaming until the cut edge feels completely smooth.

If you have used a hacksaw to make your cut, pay extra attention to removing all the burrs left from the saw’s teeth. A reaming tool and a file will help clean up the inside and outside edges of the copper pipe.

Prepare New Pipe

Ream new copper pipe that you haven’t cut if you are using a factory cut end of the pipe. Most manufacturers don’t ream and prepare their copper tubing from the factory.

4. Clean

It’s time to clean the corrosion, oxidation, and dirt from the outer area of the pipe and the fittings using sandpaper or with an emery cloth. Once cleaned, the copper will shine like a new penny!

Clean and new pipes the same as old tubing. Thoroughly sanding and scuffing the pipe ends will ensure that you get a solid and leak-proof joint when you go to solder.

The inside of your copper and brass fittings will need to be cleaned just like the outside of the pipe you want to solder. Use the properly sized wire brush and clean the copper pipe fittings inside socket area.

You also have the option of using an emery cloth by wrapping it around the finger and reaching inside the fitting. The same technique can be used with steel wool, however, make sure that your bare hands do not touch the newly cleaned surface.

6. Flux

The flux is an acidic paste, which is responsible for chemically etching the copper. As you are heating the joint, the flux will acid-clean the surface of the copper pipe, which will result in an even flow of the solder.

Use a brush to coat the mating surfaces that are going to be soldered together, which are the inside area of the fittings and the pipe ends, with an even layer of the flux. Next, push together the joint until the copper pipe seats full depth.

Solder Smarter

Clean and flux all your plumbing pipes and fittings all at once. Or divide the job into several sections. Batching all these small jobs will speed up your soldering time.

Clean and wipe off the excess flux. 

7. Heat

Grab your soldering torch and a tank of fuel and thread the torch head onto the top of the tank. In order to use it, you need to open its fuel adjustment valve then light its tip.

To make the whole lighting process easier, it is recommended to get a regulator with a built-in igniter. All you would need to do is push a button and the gas will light itself.

However, if you have a simpler torch then make sure that you get a striker too. A striker is not only simpler but also safer as compared to matches. In order to use the striker, you need to squeeze the wire handle, which will create a spark and ignite the gas.

Support the pipe and joint you are going to solder. You can use a variety of methods to stabilize the joint you are working on, just keep in mind that you will likely need both hands to solder properly. Do not hold the pipe with your bare hands as the copper heats up real fast and you could end up getting burned.

Start Soldering

Now the exciting part, you can start to heat the solder joint using the torch and let the solder flow! Light up the torch and adjust your flame to a point where the blue cone that’s in the middle is approximately 1¼ inches long. A longer cone means a hotter flame. The cone’s tip is the hottest point; hence hold your flame in a way that the tip is just touching the fitting.

Solder is not going to flow into the sections that are cooler than the melting point of the solder. So make sure you are holding the solder wire on the opposite side of the flame, to the coolest point, in order to ensure that all of the joint’s parts are hot enough.

You do not have to directly heat the copper pipe since the fitting will quickly conduct the heat to the pipe inside the joint. Once the copper’s temperature reaches the melting point of the solder, it will liquefy that solder wire which is being held against the copper and it will start flowing into the joint.

This is known as capillary action, when a liquid flows inside narrow spaces by taking no help from any external forces; hence it flows upwards as well. Therefore, you can solder copper pipes that run in any direction, whether it’s horizontally or vertically.

Keep filling the joint until the solder starts to drip out. Rule of thumb is a 1/2″ pipe will require 1/2″ of solder wire to fill the joint, a 3/4″ pipe will require 3/4″ of solder wire, and so on. Once you have solder dripping out of the fitting socket, you know it’s full.

Save Your Extra Solder

Do not overfeed your joint. Overfeeding the joint will result in a clogged-up tube thanks to excess solder buildup on the inside of the pipe.

For tubing that is bigger than ¾ inches, apply heat to the tubing’s joint from numerous sides in order to evenly raise the temperature. Then through add the copper solder in multiple spots and observe the joint in order to ensure that the solder filled the joint from every side.

After the solder socket joint is full, you can continue working on the next joint. The closest joint to the previous is typically the quickest way to work as it will already be getting warm thanks to the heat from the torch travelling up the pipe.

Watch Your Torch Temperature!

Do not overheat your solder joint. Too much heat may boil out your flux and prevent the solder from flowing correctly into the joint.

Let the joint cool for 30 – 45 seconds before handling it but extremely careful as it will still be very hot to the touch. You can cool the soldered joint with a wet rag. This will also help clean up the joint and prevent it from going green.

8. Testing Your Soldering

Now that your solder joint is full of solder and hardened you can water test it and make sure there are no drips or drips. Make sure that you flush the piping very thoroughly. Use fresh water to get rid of any extra flux, loose solder beads, or dirt inside the pipes once you complete all of the soldered connections. Plus, by flushing the pipes you will also get to inspect for any leaks. Done!

Soldering Brass Fittings And Valves

If you are soldering valves, you need to be patient. The fitting might need to be heated longer in order to raise the temperature of the joint to a point where it starts to melt the solder. Apply heat to the joint from different sides. And make sure you are leaving the valves open when you solder them.

Make sure that the valve is open to avoid pressure build-up in the tube and avoid joint leakage. Plus, if the valve consists of any rubber or soft plastic parts, then make sure you remove those pieces if possible so they won’t get ruined.

Brass fittings also require more heat than copper fittings. Apply heat at different angles or keep your torch flame primarily focused on the brass fittings. This will help the brass fittings and copper pipe heat up at the same time making your soldering quicker and easier.

When it comes to threaded adapters, make sure you solder them on a slight angle. Tilt the tube end slightly away from the adaptor to prevent excess solder from flowing into the threads.


Soldering copper pipes can be easy. Just remember measure, cut, ream, and clean before you heat and you will be a soldering machine! And don’t worry if you soldering isn’t perfect the first time, you can always flux and resolder until you get a solid leak-free joint.

Happy Plumbing!

Trevor Woods is the founder of Plumb University® and he started in the plumbing and construction industry in 1997. Since then, his mission is to make plumbing repair and maintenance easy for everyone. And each year, he continues to help more people with their plumbing installation, care, and troubleshooting.