How to Solder Copper Pipes in 7 Steps

Knowing how to solder a copper pipe, or “sweating” them as some plumbers call it, is key for proper sealing. Most homes use these pipes to distribute water from the main line to sinks, showers, dishwashers, or even to reroute a plumbing vent—and a tiny leak can cause thousands of dollars in damages if it's not fixed right away. You don't necessarily have to hire a plumber to solder copper pipes. Follow the steps in this DIY guide to learn how to solder copper pipes on your own.

What Is Soldering?

Soldering is the process of joining two pieces of metal together by heating solder, which is a metal alloy that consists of tin and lead. While a soldering iron is used for smaller soldering jobs, such as electronics, you typically use a blow torch to solder copper pipe in a process the pros refer to as “sweating the pipes.” When soldering copper pipes, you use the blowtorch to heat the solder to 600 degrees, causing it to melt around the joint between the two pipes. When it cools, it creates a strong watertight joint between the two pieces of metal.

How to Prepare to Solder Copper Piping 

Gather together the supplies you'll need for sweating copper pipes. It might be worth having a little extra copper on hand in case you need to cut a longer piece of pipe than initially expected. Always wear gloves and protective goggles when soldering copper pipes and have access to a fire extinguisher for safety reasons.

Keep in mind solder is only meant for metals like copper, brass, aluminum, and steel. This might be a factor if you're trying to decide between copper and PEX piping.

Two Tips to Join a Pipe Without Heat 

If you don’t feel comfortable wielding a torch to solder two copper pipes together, consider using these two flame-free alternatives instead. 

Copper Bonding 

Copper bonding is basically glue for copper pipes. It won’t create bonds as strong as soldering, but it requires no expertise, costs less than press fittings, and doesn’t involve a torch or applying heat of any kind:

1. Prep the pipe as you would for soldering by cleaning and deburring it. 

2. Apply a line of glue around the end of the copper pipe. 

3. Insert the pipe into the fitting. 

4. Rotate the pipe a full 360 degrees to spread the glue around the entire bond.

5. Allow the glue to dry per the manufacturer’s instructions before putting the pipe back in use. 

Press Fittings

This relatively new way of joining copper pipe uses brute force as opposed to molten metal to bond the two pipes. Press fittings don’t require a blow torch, create connections much more quickly than soldering, and require less skill. This makes press fittings similar in many ways to working with PEX plumbing. 

Though easier to execute, press fittings do require a larger investment than soldering. The press tool required to make this kind of connection costs $150 or more, and the press fit fittings are more expensive than standard copper fittings.

1. Prepare the pipe for connecting by cleaning and deburring it. Don’t skip this step as the sharp metal burr can damage the rubber ring in the press fitting that makes the connection watertight.

2. Insert the press fitting over the copper pipe all the way to the stop.

3. Use a marker to mark where the fitting ends.

4. Remove the pipe and measure from the end of it to your mark. Make sure the measurement matches the depth of the fitting. 

5. Reinsert the pipe into the fitting and use the press tool to compress the two metals together to create a tight connection (make sure the fitting doesn’t deviate from the mark you made as you do this). 

DIY Copper Pipe Soldering vs. Hiring a Pro 

Learning how to solder a copper pipe can save you the cost of a burst pipe repair or allow you to DIY renovations to your home’s plumbing by giving you the skills to connect copper pipes yourself.

However, if you don't have access to the proper materials to solder a copper pipe, such as gloves or a fire extinguisher, it's probably best to hire a local plumber with experience to tackle the job.

Hiring a plumber is also a good idea if you're uncomfortable using a torch. Additionally, excess flux on the inside of the pipes can leave behind an acidic residue, which isn't great for the water flowing through it later. 

Ben Kissam contributed to this piece.