Soldering Copper Pipe

Many older homes have copper pipe and if you need to fix a leak of any kind you will have to do some soldering. There are other ways to make these repairs, but in this article we will focus on the skill of soldering.

You can only solder copper with copper or copper with brass, everything else will not work therefore you would have to use a MIP or FIP. Which stands for male iron pipe threads and female iron pipe threads. Once these fittings are attached you can then use black iron or galvanized pipe to complete your joints.

Back in plumbing school we learned a method that worked well for soldering, therefore this will what I am going to write about today.

First thing you need to do is make proper measurements. Measure twice and cut once. When you cut into the pipe you need to use a proper copper pipe cutter. These come with a cutting wheel and two guiding wheels to help you get a perfect edge to solder with. You can use a hacksaw if you have to, but if your edge is crooked you may not get enough of a bead of solder through the joint to make a leak free seal. Sure it might last a week or two or maybe even a year, but in time this can fail.

Now you need to clean the pipe. There are two types of pipe cleaners out there, and both are pretty much the same. One is a plumbers sand paper that has a paper backing and the other is more of a mesh. In both cases these are called emery cloth.

Take your emery cloth and clean the pipe. This is more of a scraping than cleaning as small particles of copper will come off. Not like if you were using a file, but a little does come off. Now you need to do the same thing with you fitting. If the fitting is too small to get your finger or thumb into then use a pipe fitting cleaning brush. These are small wires that point outwards in a circular fashion at the end of the brush.

Now that your fitting and your pipe is clean you need to apply some soldering flux to the outside of the pipe and to the inside of the fitting. This also helps to clean the copper as you heat it, but is also meant to help the solder flow while you are soldering the copper pipe.

Oh, by the way, I am using the term copper pipe quite loosely here, in actual fact the term is called copper tube. There are three types of copper for plumbing, tubing, tube, and pipe. The long straight lengths you see on trucks and in your local hardware store are tube, while the coils come in longer lengths and are more used for gas fitting where it is against the code to solder. In these cases the gas fitter would use flared fittings to join the pipe. The tubing can be used for water lines in which case compression fittings are used. You may have seen these on dishwashers and ice makers. Real copper pipe is threaded and not soldered and is used for industrial purposes.

Before you start to solder the copper pipe you will need to have the right kind of solder. If you are soldering a joint for a vent or drain then you can use 50/50 which is 50 % tin and 50% lead. Do NOT USE this on water lines. Also not recommended for heating systems as the melting temperature is lower than other types of solder. For water lines you can use 95/5 tin/antimony or lead free solder. Both are lead free just have different names.

Now let’s get soldering, make sure you have proper ventilation and some sort of fire resistant material is you are close to anything flammable. Turn on your torch and point the blue part of the flames tip at the joint you want to heat up. Now touch the joint from time to time with your solder to see if it is hot enough yet. Once the solder starts to melt you should pull the torch back a little so you do not over heat the fittings.

Make sure you get a good bead of solder all the way around the joint. In school it was mandatory to wipe the joint, but in reality nobody ever does.

If you have problems soldering because there is water in the line you will need to get all of the water out to make a proper joint. There are tools that allow you to solder on a valve with water in the line but these are expensive and can only be used to solder on a valve, MIP or FIP to tie onto later.

A quick fix if you can solder fast is to shove a slice of bread into the pipe and poke it up the pipe as far as you can. If the leak is small this should give you anywhere from 30 seconds to 3 minutes to get the job done. If the leak is bad enough that the bread does not hold for thirty second you may have to get someone in to freeze the pipe. If the bread holds the leak for more than 3 minutes then most likely you could have used a hotter torch and kept the steam back while you soldered the copper pipe.

The reason you cannot solder with water in the line is because when water expands to steam there is an increase in volume of about 1700 times. Even if the joint did get hot enough a lot of times this increase in volume causes steam to push the solder out of the joint. Watch your eyes in this case as the solder will spray and is very hot.

I hope this helps you one you copper soldering project.