How to Solder Copper Pipes
What are you trying to solder? New pipes that are bright and clean from your local Home Depot or are you trying to make a repair on some old nasty green patina covered specimen that finds its home under yours? Perhaps with spider webs covering it? Let’s treat them both the same and you won’t have any problems or call backs as we used to say in the business.
Copper pipes and fittings must be clean to solder together. Not just looks clean but actually clean through the first layer of metal. I know that may sound strange but trust me here. I think I can count on 1 hand the number of water leaks that I’ve ever had and I have soldered a lot of copper pipe. To accomplish this task of uncovering the pure element of copper you must scour the surface hard enough to scratch through anything that might be in the way. This can be done with emery cloth or sand paper for the piping and male fittings. Just the ends of the pipe or male fitting needs to be cleaned and I give is an extra in or so above where it will be slipping into its fitting. A properly sized wire brush is what is needed for the female fittings. These brushes can come in a combo that includes 1/2″ and Ã?Â¾” which is almost all you will ever find in a residential setting. Some of these combo brushes also include an outer brush for cleaning up pipe and male fittings but I recommend emery cloth because I like to get it clean, really clean. When you get it there you will have no sign at all of any dark or discolored metal just bright and shiny scratches.
Once you have the pipes and fittings that you are going to use clean. You need to flush the male ends of the pipes and fittings. I use Oatley Tinning Flux but other brands can be use but don’t be cheap get the stuff the pros use and that would be one type of Oatley or another. Just check the labels. The purpose of the flux is to draw the solder into the joint completely. It also is a bit acidic and helps with that all important cleaning. You do not need to glop the flux on but use the small flux application brushes that should be on the same shelf to put a nice layer all the way around the pipe. When you slide the pipe into the fitting you should have a nice rim of flux that is pushed out of the fitting. Remember all the way around.
O.K. you got it cleaned and fluxed. Now is the time to light er’ up. I use a Mapp gas cylinder and an inexpensive torch to do the job. Mapp gas gets hotter quicker than propane and for the small increase in price it will save you a lot of time heating up soldering joints and get you done quicker. Get a medium setting going on the torch because all out is not needed. Place the tip of the flame on the female fitting angled towards the pipe or male fitting if possible. This heats the area that we want our flux to draw the solder into. Have your solder ready in hand with a small amount of it bent at a 90 degree angle. Rule of thumb is that if you are soldering a Ã?Â¾” joint you would need about Ã?Â¾” of solder. But if you use more than that your first few times you are doing alright. If you watch closely you will see the flux begin to melt, bubble and then disappear. When it disappears into the fitting you are getting very close to being able to put the end of the solder in the groove that the fitting and pipe make where they meet. Wait a few seconds and then try. If it is hot enough the solder will flow into the joint and if it is not hot enough it might not melt and may even get stuck to the pipe. If this happens just keep the heat on and it will melt and flow.
How do you know if there is enough solder in the joint? Watch as the solder flows and when it seems to have flowed completely around the joint you have it. If you are not sure you can put a bit more solder to the joint while it is hot but most of it will just go on the floor. I sometimes take the flux brush while the joint is still hot enough for the metal to flow and apply a little flux around the fitting to be sure I have good coverage in the joint.
A few tips for problems you may encounter;
Wet pipes or pipe with water in them will not solder. You will have to do whatever you need to to get the water completely away from the joint. Once that water turns to steam as you apply heat and desperately apply solder you are not going to win.
I have used a shop vac and some duct tape to pull a vacuum on the pipes to clear all the water in the lines and then needed to hurry and get the joint done before the water made its way back to where I was soldering. I have also heard of old timers using a small wad of bread to fit it tightly into a leaking pipe to hold back a small trickle while doing the task. They also sell professional beads that do the same things which is dissolve is water after a few minutes.
That is way more information than I ever had starting out and I hope that it helps. Good luck.
Torch head and Mapp gas tank, emery cloth, flux brush, wire fitting brushes and pipe cutter.