DIY Home Improvement Forum banner

How To Solder Copper Pipes

68K views 69 replies 24 participants last post by  Chokingdogs 
#1 ·
Here's a very basic pictorial lesson on soldering copper pipe together. I'll hit on the high points...

The first picture is what you'll need for basic work on copper pipes:
  • Torch. The one pictured has a hose to the torch head, which is very convenient. I prefer mapp gas over propane just because it gets hot fast. Propane works fine...I'll cover that later on.
  • Pipe/fitting cleaning brush. You have to have a wire brush to clean the inside of the fittings. The brush pictured is a combination brush that cleans both the fittings and the outside of the pipe, in both 1/2" and 3/4". Emery cloth is also great for cleaning pipes, but not fittings.
  • Flux. I like the stuff in the picture. It is a dark cruddy amber color and is very thick. I do not care for the black or dark gray stuff that usually comes in the small tins and "kits"...That stuff is too thin.
  • Pipe cutters. Don't use hacksaws or sawzalls unless it can't be avoided. Tubing cutters don't deform the pipe. It is also a good idea to deburr the end of the pipe after cutting it, and many pipe cutters come with a tip for doing that.
  • Solder. Plumbing solder!
  • Have a rag handy for wiping up the fittings after soldering.
  • Wear shoes and long pants. Hot dripping solder that hits the floor splatters liquid hot metal in all directions. It hurts if it hits you.
  • It is also wise to have a fire extinguisher handy. You never know. Fire and hot metal don't mix well with some interior surfaces.
  • Pipe and fittings. Duh.
  • Labrador retrievers are optional
 

Attachments

See less See more
1
#5 ·
Then flux is applied to the fitting and the pipe. The way I see it, the stuff is cheap, so I use plenty. Pros probably use less. More isn't necessarily better, but a thorough coat on all surfaces is critical. Be sure it is free of sawdust or bristles from the flux brush.

Put the fitting and the pipe together. Be aware that as soon as you heat it, it'll want to move because when the solder melts it gets a lot more viscous. So, when doing this, orient your fittings so gravity won't cause them to rotate on you.
 

Attachments

#6 ·
For the record, this fitting rotated because I left it horizontal for photo purposes. I'd normally do this vertically whenever possible.

Heat is applied to the fitting (not the pipe). The solder will be drawn into the flux TOWARD THE HEAT. So here, I'm heating the underside and the solder will be touched to the top side of the fitting hub.
 

Attachments

#7 ·
I didn't get a picture of it, but I roll several inches of solder off the roll and use the roll as a handle to keep my hand far enough away that molten flux and solder won't drip on it.

Apply the heat. Hold the torch head about 4" away. Watch for the flux to melt and start to boil. Just heat one area of the fitting...The heat will conduct to the entire fitting. You'll see the color of the copper sort of change a little bit, kind of like watching water freeze and expand on a very cold windshield. When you see that, time to apply solder and back the heat off.

The solder is TOUCHED to the side of the fitting opposite the heat. If it melts instantly your fitting is hot enough and you can pull the torch away. Feed the solder into the joint until you see it come out the other side. I feed it in until a drip forms. It doesn't really take much because you're filling a very tiny gap.
 

Attachments

#8 ·
In this picture you can see where I touched the solder to the fitting/pipe joint. THERE IS NO NEED TO MOVE THE SOLDER AROUND, JUST TOUCH IT IN ONE PLACE. This isn't welding. Any solder that you see on the outside of the joint is just extra and isn't the solder doing the work of keeping the water back.
 

Attachments

#11 ·
Valves and other brass fittings...

They can be tricky for a first timer. Brass seems to take more heat than copper, probably due to the fact that it is thicker than the copper pipes and fittings more commonly soldered.

With valves, be careful not to heat the guts if you can help it. Shower valves' inner workings should be removed before heating. You have to remember to orient the valve so that liquid solder doesn't run down into the valve and cause things not to close or parts not to fit.
 
#13 ·
Sometimes people ask "can I re-heat the joint or add some solder if there is a pinhole leak?" My answer is always no. The pinhole leak is there for some reason, and globbing extra solder on the outside is a band aid. Leaks will form in areas where the flux completely melts out, so the solder just won't go there. Re-heating won't work most of the time. So, I usually advise re-heating and removing, cleaning the pipe, cleaning (or replacing) the fitting, and trying again.
 
#14 ·
Any water in the pipes will be drawn toward the heat you are applying. Do whatever you can to drain all the water out. You can't solder pipes with water in them. It cools the joint just enough, and will often cause a lousy seal resulting in a leak.

There are ways to keep the water at bay when necessary. I use bread. There are commercially available products like the little gel-filled eggs they sell at the big box stores or more professional products like Jet Swet that are inserted into the pipe and removed after finishing. White bread formed into a doughball can be jammed a few inches into the pipe will hold the water and steam back, and will liquify into something resembling baby vomit instantly when water pressure is restored to the pipe. Just open a downstream valve to clear the line. Some people say to remove the aerators from the sinks or to let the toilet supply lines shoot into a bucket to avoid getting the bread into the fixtures. Personally I've found that it clears out within seconds and doesn't hang up in the fixtures. Common sense prevails...Don't use the crust and don't use any kind of grainy bread with seeds and chunks of anything. Its a great trick that a master plumber taught me years ago, and I've used it a hundred times with great success.
 
#17 · (Edited)
Hopefully some other folks will have some other tips or scenarios to make this thread more informative. :yes:
I'll take The KCTermite up on that.

1. The purpose of sanding the outside of the copper pipe is not to clean it of oils. The purpose is to remove the copper oxide that forms on copper when it's exposed to air. That oxide film forms slowly at room temperatures, but almost instantaneously at soldering temperatures (or from about 350 to 450 deg. F, depending on the solder you're using.)
Copper is an orangy/gold colour, but Copper oxide is brown in colour, and it's the formation of a copper oxide film over the copper that causes new pennies to turn brown in time. Ditto for copper piping and everything else made of copper.

Oxygen atoms hold onto their outer electrons very tightly. Metal atoms, on the other hand are very loose with their outer electrons, and it's this difference that prevents metals from having a high affinity for oxygen or even metal oxides. Liquid metals, like molten solder, have a very high affinity for bare copper metal, but little to no affinity for copper oxide. In order to get the solder to stick properly to the copper of the pipe and socket, it's necessary to remove all the copper oxide from both AND prevent it from forming during the soldering process. Only then will there be enough capillary pressure drawing the heavy liquid solder into the joint to fill it completely. Any copper oxide film on the pipe or socket will prevent the molten solder from sticking to the copper oxide, resulting in a leaking soldered joint.

2. Soldering flux consists of petroleum jelly (which is what "Vaseline" is) with zinc cloride powder mixed into it. The purpose of the flux is threefold:
A) it prevents an oxide layer from forming on the bare copper
B) it cleans the bare copper of any remaining oxide on it, and
C) it promotes good flow of the solder by keeping the copper metal bare until it is displaced by the solder.

3. The petroleum jelly's job is to prevent oxygen from the air from coming into contact with the bare copper metal while the joint is being soldered. So, in that respect it merely acts as a physical barrier between the copper and the surrounding air. So, you can solder using Vaseline as flux, but the solder will only flow into the joint. It'll beed up on the surface of the copper pipe because the Vaseline outside the joint quickly burns off and exposes the bare copper metal to oxygen in the air.

To prove this to yourself, next time you solder a joint, sand an entire foot (12 inches) from the end of the pipe and flux that entire foot. After you solder, allow everything to cool and clean off the residual flux from that entire foot, you'll find that the entire 12 inches before the joint is clean and bare, just like it was before fluxing and soldering. The flux on the copper pipe prevented the pipe from oxidizing and discolouring as usually happens on sanded copper piping near the solder joint (or source of heat).

4. The zinc cloride acts like an acid. At soldering temperatures it dissolves any residual copper oxide in the joint that wasn't removed by sanding. It dissolves the copper oxide much more aggressively than the copper metal.

5. When you solder a joint, what actually happens is that the molten solder has a greater affinity for the bare copper metal than the flux does, and so it's CAPILLARY PRESSURE that draws the molten solder into the joint to displace the flux inside it. Once the molten solder is in the joint, something called "amalgamation" occurs in a very thin film at the solder/copper interface. That thin film consists of an alloy of the copper and solder that results when the two dissolve in one another. Some of the tin and antimony (or lead) atoms dissolve in the solid copper and some copper atoms dissolve in the molten solder right at the surface of the copper.

(The following was told to me by my metallurgy prof in University. I tried to find a website to confirm in Google, but was unable to.)

If you ever unsolder a joint, you'll find that you cannot completely remove the old solder from the end of the pipe by heating with a torch and wiping. That's because the melting point of the alloy formed at the amalgamation plane varies from that of solder on it's outside to that of copper on it's inside. So, the "solder" doesn't wipe off because it's not molten because it's no longer pure solder with the melting point of pure solder.

6. Everything from sanding the copper pipes to adding zinc chloride to the flux is designed to prevent copper oxide from forming inside the joint. At soldering temperatures, that oxide layer will form instantaneously. So, if for some reason (like not allowing a path for the heated air inside the pipe to escape) the solder isn't drawn all the way around the joint, then adding flux and solder when the joint is hot will (at best) just plug up the leak in the solder joint. It won't end up filling the joint with solder. The reason why is that while you are soldering, the flux won't burn because there isn't any oxygen inside the joint for it to react with. If air inside the pipe expands and leaks out through the fluxed joint, the flux exposed to air will burn off, exposing the bare copper metal that will immediately form an oxide film over it. After that, the molten flux will NEVER bond properly to that oxide film because oxygen hordes it's electrons. The best that you can hope for is that you can plug the END of the leak in the joint with solder. But, that's just a leak waiting to happen.

7. So, how does this affect what you do? Understanding the process allows you to understand why it's seldom necessary to remove old solder from old pipes or sockets. If you unsolder a copper pipe from a socket, you're best bet is to NOT remove the solder from the socket or the end of the pipe. That solder in the socket or on the end of the pipe will protect the underlying bronze, brass or copper from oxidation. Just leave the solder on the end of the pipe or in the socket until you need the pipe or valve. Then, when you need that piece of pipe, just heat the end of the pipe and wipe the old solder off. If it's a valve, heat the socket of the valve and insert a piece of sanded and fluxed copper pipe into it until it goes into the socket, and then pull it out, thereby removing the old solder from the socket. (Repeat if necessary) Then clean the end of that pipe with steel wool or a piece of sandpaper to remove any oxides that may have formed while the pipe was cooling down. Brush out the socket. Flux the pipe end and the ID of the socket and fit them together (even if both appear to be still covered by solder). Now just heat and add enough solder to ensure the joint is full (by the formation of a drop of solder on the bottom of the joint as discussed by KCTermite). That solder joint will be just as strong and last just as long as had you gone to the trouble of using a new pipe and sanding the old solder out of the sockets of the old valve. In fact, it'd prolly last longer because by not sanding the old solder out of the sockets, you're not enlarging the ID of the socket.

PS:
To learn more about soldering and brazing copper, brass and bronze, go to the Copper Development Association's web site at:
http://www.copper.org
and click on the "Publications" link,
then click on the "Publications List" link
then RIGHT CLICK on the "Soldering/Brazing/Welding" link on the list on the LEFT column of links, and chose "Open in new Window".
Then download everything you want.
 
#19 · (Edited)
Here is a direct link to the Copper Development Association's download page for soldering, brazing and welding copper:

http://www.copper.org/publications/pub_list/soldering.html

There's a 1.1 MB PDF file you can download that provides helpful tips on soldering and brazing copper.

There's an 8 page PDF file that gives step-by-step illustrated instructions on soldering and brazing copper tube and fittings.

There's also an 18 minute long video you can order for $25 on soldering and brazing copper tube.

And there are other paper pamphlets you can order for a small fee or PDF files you can download free.

Also, I forgot to mention a few things in my last post:

A) Experienced plumbers will often bark at me for telling people that it's OK to use the soldered end of a piece of copper pipe. They feel that's bad advice because they believe it's "safer" to start with new pipe. All I can say is that when I discussed the matter with the department head of "Piping Trades" at the local provincial trade school here in Winnipeg, "Red River Community College", he advised me that was standard plumbing practice. He also recommended cleaning and fluxing the pipe end to remove any oxides of lead, tin or antimony that may have formed, but it's not necessary to remove all of the old solder, especially from sockets which are much harder to remove that old solder from than pipes.
In my own case, whenever I have to remove a Brasscraft compression stop in order to remove a section of wall, I always solder the old valve body back on after the work is done using the procedure described above. I've never had a leak doing that.

B) It IS true that when you're soldering in a valve, it's best to remove the cartridge from the valve to protect it from the heat. The exception is when you're soldering in a ball valve. In that case, you're more likely to cause a leak by taking the ballvalve apart to remove the ball and seals and then putting it back together than you are by soldering the valve in as is.

When soldering ball valves, Just make sure that the valve is in the open position. Also, when brushing out the sockets on the valve with a fitting brush, drop a standard #12 flat washer into the socket before brushing. A #12 flat washer will have a 1/4" ID and a 5/8" OD, and it will prevent the steel bristles of the fitting brush from coming into contact with the teflon seals inside the valve. That ensures that the seals aren't damaged by the fitting brush.

C) Some valve manufacturers are now selling globe and gate valves that don't have a fiber washer or gasket between the bonnet nut and the valve body. They simply tighten up the bonnet nut so tight that the valve doesn't leak even with a metal-to-metal contact between the bonnet nut and valve body. And, of course, they tell the user to just solder the valve in when it's partially open to protect the washer from the heat. That's dumb because when the time comes to replace the washer, you're more likely to wreck the soft copper piping the valve is soldered into than remove that bonnet nut. And, after replacing the washer, then you somehow have to tighten the by-Geezus out of that bonnet to get a water tight metal-to-metal seal again (without wrecking the copper piping).

There's a better way. Before installing the valve, put it in a vice and remove the bonnet. Now, go to any place listed in your yellow pages under Pneumatics and Hydraulics that sells rubber O-rings and inquire about "teflon back-up rings". Teflon back-up rings are used to prevent the O-ring from extruding into the empty space around it. So, some teflon back-up rings will have a contour on one side of the ring, but most are simply machined from a tube of teflon and so they are flat on both sides. Tell the guy you want a teflon back-up ring without a contoured side.

Teflon back-up rings come in a vast array of sizes starting with ID's of 1/8 of an inch all the way up to 12 inches with widths (difference between outer radius and inner radius) of 1/16", 3/32", 1/8", 3/16" and 1/4 inch, and most places will also stock popular metric sizes as well. So, you can always find a teflon back-up ring to fit your valve and serve as a gasket between the valve body and bonnet nut to prevent leaks.

Also, if the bonnet nut on a valve has 8 sides, that generally means you're not supposed to remove it, and that generally means that there is no fiber washer or gasket between the valve body and the bonnet nut. If you're wanting to use this valve inside a wall as a bathroom water shut off valve, or any other place where you can't use a wrench to remove the bonnet nut, you can modify an 8 point socket to make a tool for removing and tightening the bonnet nut. Just look for an 8 point socket you can put in a lathe and machine down the points so that each point contacts the middle of a flat on the bonnet nut. Then you essentially have a flank drive socket (like a Snap-On) to loosen and tighten eight sided bonnet nuts.

The ratio to find the size of 8 point socket needed to fit over an 8 sided bonnet nut is:

cosine of 22 1/2 degrees or 0.92388

So, if the bonnet nut is 1 1/4 inch across the flats, you'd need a:

(1.25) X (0.92388) = 1.155 inch 8 point socket.

That works out to a 1 5/32 inch 8 point socket which you won't find anywhere. So, buy the next smaller size (1 1/8 inch) socket and have the points machined down on a lathe until it just fits over the bonnet nut.
 
#23 ·
Two points often overlooked.

Wipe the joints with a wet rag after soldering to remove the excess flux. Remaining flux will continue to etch (eat) the copper pipe.

Deburring/reaming of the cut edges of the pipe is also very important. The sharp edge will create turbulence in the water, causing friction and pipe wear.
 
#34 ·
I have a question! The code in my area requires that we would use 'silver' solder, rather than 'lead'.
My question is, can I still use the 'Vaseline' paste that I have on hand, or does it require a special paste designed for silver?
Lead solder hasn't been sold in stores in many years. About the only place you'd pick it up is at garage sales and at your Dad's house.
The solder paste sold today is also lead free.
The ,"vaseline" reference will be confusing to the newbies. You don't use that in soldering.
Ron
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top