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How To Sweat Solder a Copper Pipe

By Edited Jun 9, 2016 0 0

Many homes have copper pipes carrying its occupants their water supply. As with most homes, issues will arise in various areas in the house or you may find you need to add something or take it away. Your plumbing system is part of that too. Sometimes sections of copper piping can become damaged from impact or frozen pipes that may burst. Some do it yourself type homeowners look to add on to their plumbing system whether adding a new bathroom, laundry room or utility sink.

First off let me start by saying, no plumber would ever call this sweat soldering so if you speak to one just tell them you are sweating in a new pipe. Homeowners tend to call it soldering and the real term is sweat soldering, but professionals shortened it to sweat or sweating. If you need to add to existing plumping or repipe your plumbing, the first thing to keep in mind, the golden rule if you will, use like metals. Do not try to attach copper fittings to cast iron pipe or vice versa, it won't work.Dissimilar metals will go through a process known as galvanic reaction, which mean the metals will react to each and degrade. Galvanic reaction will destroy your pipes.

Prepare the Copper Pipe and Fitting

Clean the ends of the copper pipes that are to be joined together. The ends need to be very smooth. Use a piece of very 320-grit sandpaper, plumbers emery cloth or a wire pipe brush that fits into an electric drill.

Rub the abrasive material around the inside of the pipe and the outside of the that will fit into it. Make sure the copper turns smooth and shiny.

Do not use steel wool, a file or rasp because they leave behind small copper shavings, burrs and scars on the pipe and fitting.

Get Ready To Sweat The Pipe

As soon as you have sanded the copper fitting and pipe to a shine, apply soldering flux to the inside of the fitting and the end of the pipe. Typically, soldering flux has a small brush attached to the inside of the lid so you can spread the flux. Soldering flux can be purchased in

Repair Copper Pipes
hardware stores and home improvement stores.

Place the end of the pipe into the fitting and push it in as far as it will go by hand. Do not bang or hammer the pipes together.

Turn the pipe a couple of times to completely and evenly spread the flux on the inside of the fitting.

Use a clean rag to wipe off any excess flux that may have squeezed out of the copper fitting.


Use a propane torch to heat the pipe and fitting. Move the torch flame around the edge of the fitting to heat it, do not leave the flame burning steadily in one place, keep the flame in motion.

Keep waving the flame over the copper pipe and fitting until it becomes very hot.

Use lead free solid core solder. Touch the solder to the edge of the fitting, if the pipe and fitting are hot enough, the solder will melt and run a ring around the edge of the fitting to seal it.

Do not use the flame from the torch to melt the solder, the heat emitted from the copper pipe and fitting should be great enough to melt the solder.

If the solder did not melt and run a ring around the pipe and fitting, continue to heat the area with moving heat from the propane torch.

That's it -- done!


Wear heat resitant gloves when sweating copper pipes.

Wear safety glasses.

Move all flammable materials out of the area prior to lighting the propane torch.






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