How to Solder Copper Pipe

Soldering copper pipes is an essential skill for plumbers, HVAC technicians, and DIYers. With the right tools and technique, soldering copper is a straightforward process that allows you to make watertight joints in copper piping systems. This guide will teach you everything you need to know about soldering copper pipe.

Gather the Necessary Materials

Before you start soldering, make sure you have all the right supplies on hand:

Copper Pipe

You can solder any type of copper pipe including Type K, Type L, and Type M. Type M is the most common. Make sure the pipe is clean and free of dirt, oil, or oxidation before soldering.

Lead-Free Solder

Use lead-free solder that contains tin and silver or tin and copper. Lead solder is banned for potable water systems. A solder wire diameter of 0.5mm or 0.04″ is good for most applications.


Flux helps clean and prep the copper surface for soldering. Use a liquid or paste non-corrosive flux specifically made for copper soldering. Apply flux liberally to both the pipe and fittings.


Have the necessary fittings on hand including elbows, tees, couplings, end caps etc. Fittings must be lead-free and match the pipe size.


A small handheld propane or butane torch works best. Adjust the flame to a sharp blue cone about 1-2 inches long.


Sandcloth helps polish and shine the copper surface for soldering. Emery cloth or very fine grit sandpaper also works.

Wire Brush

Use this to scrub the pipes and remove oxidation or residue after sanding but before soldering.


Have a dry cotton rag handy to wipe away excess flux.

Safety Gear

Wear safety glasses to protect your eyes from debris when sanding or brushing. Leather gloves also help protect your hands from heat.

Prepare the Copper Pipes

Proper preparation is crucial for getting a good solder joint. Follow these tips:

  • Cut the pipe to the required length using a tubing cutter. This will give you a nice straight cut. Avoid hacksawing as it can flatten the pipe shape.
  • Deburr the end of the pipe using a reaming tool. This removes any sharp edges or ridges from cutting.
  • Clean the last 1-2″ of the cut pipe end and the inside of the fittings using sandcloth. Scrub until you see the copper shine.
  • Further buff the sanded areas with a wire brush to remove any residue or oxidation.
  • Wipe away any dust or particles with a dry rag.
  • Apply a generous amount of flux to the sanded pipe end and inside of the fitting. Spread it around using a flux brush.

Assemble the Pipe and Fittings

Once prepped, you can assemble the pipe and fittings:

  • Slide the pipe and fittings together. Use a slight twisting motion to fully insert the pipe into the fitting.
  • Ensure the pipe is contacting the bottom of the fitting cup. There should be no gaps.
  • If needed, mark the joint depth on the pipe. The fitting should go on at the same depth when soldering.
  • Reapply flux if needed before soldering.

Solder the Joint

With the joint assembled, you can move on to soldering:

Step 1 – Heat the Fitting

  • Light your torch and adjust it to a sharp pointed blue flame.
  • Start heating the cup of the fitting first, focusing the torch flame on the bottom inside.
  • Gradually move the flame around the fitting cup edges. Avoid directing the flame on the pipe.
  • Heat until the flux starts bubbling.

Step 2 – Add Solder

  • With the fitting hot enough, touch the solder wire on the opposite side of the cup away from the flame.
  • The solder should melt immediately when contacting the hot fitting. If not, apply more heat.
  • Allow the molten solder to flow into the cup and around the joint as you move the torch flame around.
  • Remove the wire once the solder fills the fitting cup flush with the pipe.

Step 3 – Cool and Clean

  • Allow the joint sit undisturbed as it cools. This takes only a few seconds.
  • Wipe away excess flux with a dry rag once cooled. Avoid disturbing the joint before it sets.
  • Scrub off any drips or splashes using a wire brush.
  • Visually inspect the joint. It should show a thin line of solder around the pipe and fitting.

Tips for Good Soldering Technique

Follow these tips to master proper soldering technique:

  • Always solder pipes horizontally when possible. It’s easier than vertical joints.
  • Position the pipe and torch so you can see the joint as you solder.
  • Torch angle is key. Aim the flame towards the fitting cup, not the pipe.
  • Heat the entire area around the pipe before adding solder.
  • Touch the solder on the opposite side from the flame and let it “chase” around the joint.
  • Avoid moving or bumping the joint as the solder sets. Stay steady.
  • Apply only as much solder as needed to fill the cup flush. Excess solder is problematic.
  • Re-sand and reflux if needed between soldering attempts.
  • Let joints cool fully before disassembling or moving onto the next joint.

Troubleshooting Soldering Problems

Even experienced plumbers have the occasional soldering mishap. Here are some common problems and solutions:

Problem: Solder won’t flow into the joint.

Solution: Insufficient heat on the fitting cup. Increase torch heat until you see smooth solder flow.

Problem: Solder drips off the joint.

Solution: Too much heat. Reduce torch angle and move flame slower around the fitting.

Problem: Joint leaks after soldering.

Solution: Pipe not fully inserted into the fitting before soldering. Disassemble, clean, and resolder.

Problem: Solder blobs around the pipe rather than filling the fitting.

Solution: Heat was focused too much on the pipe rather than cup. Aim flame inside the fitting.

Problem: Burnt flux residue on pipes after soldering.

Solution: Rinse pipes with water immediately after soldering to remove residue before it bakes on.

Problem: White powdery deposit around joints.

Solution: Join was overheated when soldering. Often still seals ok but re-do for a cleaner look.

Safety Tips for Soldering Copper

Soldering can get very hot. Follow these precautions to work safely:

  • Wear eye protection and gloves when soldering.
  • Avoid touching heated parts. Allow joints to fully cool before handling.
  • Keep a fire extinguisher and first aid kit nearby.
  • Work in a well-ventilated area to avoid fumes.
  • Secure pipes with clamps or vises so they don’t shift when hot.
  • Never use a torch near flammable materials or gases.
  • Use lead-free solder for any potable plumbing application.
  • Wash your hands after soldering, especially before eating.

Common Copper Pipe Soldering Applications

With some practice, you can use soldering for all types of residential and commercial copper plumbing applications including:

Plumbing Repairs

  • Fixing leaks in existing pipes and joints.
  • Repairing burst pipes by splicing in a new section.
  • Replacing a damaged fixture tee or elbow.

New Installations

  • Joining copper supply pipes to fixtures like faucets, water heaters etc.
  • Connecting copper to valves, pressure regulators, filters.
  • Installing irrigation systems with copper distribution pipes and emitters.

HVAC Systems

  • Soldering copper refrigerant lines and condenser coils.
  • Joining copper water pipes on heating systems like boilers and radiators.

Other Building Systems

  • Soldering medical gas and compressed air copper lines.
  • Joining copper tubing for fire suppression systems.
  • Solar hot water systems using copper manifolds and heat exchangers.

Frequently Asked Questions

What type of torch do I need for soldering copper pipe?

A basic handheld propane or butane torch with adjustable flame works well for most general copper soldering jobs. Miniature pencil torches are good for tight spaces. High capacity torches may be needed for very large pipes.

Can I use lead solder on copper plumbing?

No. Lead solder is banned by federal law for installation or repair of any potable water systems due to the health risks of lead leaching into drinking water. Always use lead-free tin alloy solder.

What is the proper soldering technique?

Focus heat evenly around the cup of the fitting to warm it first before adding solder wire to the opposite side. Let the solder melt and flow into the joint as you move the torch around the fitting. Avoid applying direct flame to the pipe.

How long does it take for a soldered joint to cool and become sealed?

It usually takes only 10-20 seconds for a soldered copper joint to cool enough to be handled and seal the joint. However, it’s best to let it sit undisturbed for a minute or two before moving.

How can I get old solder joints apart?

Apply heat evenly around the joint with a torch until the solder re-melts. Separate while still hot. You may need to wiggle pipes as the solder softens. Be careful not to distort the pipe.

Is soldering hard to learn?

Basic soldering is not difficult but developing good technique takes some practice. Key tips like proper torch angle, applying even heat, and touching solder wire correctly can take a few tries to master. Practicing on scrap pieces first helps.

What is the best tip for preventing drips and blobs when soldering?

Avoid overheating the joint. Moving the torch flame around the fitting cup slowly and concentrating heat right on the cup gives a nice flow of solder into the joint without drips on the outer pipe.

Can I solder copper without flux?

It’s not recommended. Flux cleans and preps the copper surfaces, aids heat transfer, and allows the solder to adhere correctly. Soldering without flux often results in a poor joint.


Soldering copper pipe is a must-have skill for creating strong, watertight plumbing, HVAC and general piping systems. Follow the steps here to prepare, assemble, and solder joints properly. With some practice you can master good torch technique. Safety is also paramount when handling hot metal. Use lead-free solder and take precautions. Once you get the hang of it, you will find soldering copper to be an enjoyable and rewarding skill.