Help with sweating copper

[Wade Lippman]

I have to run a new line to an expansion tank, incorporating a valve and faucet. I have done a hundred joints, but none for 15 years and I am a bit nervous. It is all 1/2", which I recall was really easy.

What has me concerned is that I once had trouble doing the second side of a coupling without having the first side fall apart. It was in a 2' crawlspace under a house, so I have an excuse, but still... Any tips would be appreciated.

[Peter Kelly]

If it isn't that long or complicated of a run and you're nervous, you may want to just get some Sharkbite fittings instead of sweating everything.

[Bruce Wrenn]

To make your life easier, get some LACO brand flux. You will probably have to go to a plumbing supply house to buy it. Clean joints, apply flux to both pieces of pipe, fitting and assemble joint. Pick one end or other of fitting, and apply heat to both pipe and fitting. If fitting is in a vertical position, apply heat to bottom side first. Remember that heat rises. After bottom is soldiered, place soldier on other side of fitting and repeat. The valve body will require a lot more heat than a coupling. Be sure valve is in the open position. Make up as many of the fittings on the bench as possible, so you only have one to do one in place.

[Tom M King]

For a coupling, or elbow, or any such fitting, I do both sides with the same heating. It makes no sense to do one side, and then the other. It's fine, and normal to move the torch while the assembly is being heated.

If needed, prop something under it so it doesn't fall apart, but I can't ever remember having to do that. If the valve needs to be soldered too, solder that to the pipe it mates to, let it cool off, and then do both sides of the coupling. The coupling will be heated enough for the soldering before the valve absorbs enough heat to melt its solder.

Hot air rises over colder air, for maybe obvious reasons, but heat itself doesn't rise. It's not part of the situation here.

If the "faucet" is close to the heating of the pipe, and has a rubber washer in it, screw the guts out of it until the soldering is done, and it has cooled back off.

[Lee Schierer]

Clean all surfaces that will be soldered before assembly. Even if the copper looks clean, clean it any way.

[Paul F Franklin]

Proper cleaning is the key to easy, good joints. I use plumbers tape for the pipes, and one of the purpose made wire brushes for inside the fittings. You want bright copper inside and out. After the tape and the brush, I use a clean rag dampened slightly with alcohol to remove the sanding/brushing residue and the oily residue that is often on the pipe and fittings. Then a good quality flux, inside and out. If you have to buy flux, consider tinning flux, which has a small amount of ground up solder in it. When the joint is hot enough, the solder in the flux will flash silver, and then you know to apply the solder.

Don't overheat the joint and burn the flux. A 1/2" joint doesn't take much heat. Heat the pipe next to the joint a little first, and then the fitting. When you apply the solder, you should see it suck into the joint; if you don't, you need a touch more heat.

Don't disturb or wipe the joint until it is fairly cool. Then use a wet rag to remove all the flux residue or it will corrode the joint over time.

The lead free solder one uses today does not flow quite as easily as the old tin/lead that you likely used before, so resist the temptation to really load up the joint with solder. Once the pipe and fitting are hot, a quick swipe around the joint with the solder is enough. The lead free solder also doesn't have the shine the leaded solder had, so don't assume a slightly dull joint is a bad joint.

Buy some extra pipe and and a fitting or two and practice; you'll quickly remember how it goes.

[Tom M King]

When prepping the inside of a fitting with the round wire brush, only go the direction that allows the bristles to lay down. If you go back and forth, or any against the slant of the bristles, it will just bend the bristles, and fray the brush. It might clean that fitting okay after that, but it won't be good for many more. Only go the right direction, and the brush will last for hundreds of fittings.

I got my plumbers license in 1976, and all water lines around here were copper for at least another decade.

[Jim Becker]

If it isn't that long or complicated of a run and you're nervous, you may want to just get some Sharkbite fittings instead of sweating everything.

This. They work well with both copper and PEX....as long as you FULLY insert the pipe into the fitting, wink, wink...nod, nod...and there's zero sweating required.

[Bruce Wrenn]

I got my plumbers license in 1976, and all water lines around here were copper for at least another decade.P-1, or P-2? When I started in the plumbing trade, I didn't need a licensee, because I lived in a town area with a population of less than 5000. Then I got my P-2,followed by my P-1 as the area grew.

[Bruce Wrenn]

Clean all surfaces that will be soldered before assembly. Even if the copper looks clean, clean it any way.


Not necessary when using LACO flux as it's self cleaning. Unless fitting / pipe is covered in dirt, or "green" when the heat hits the LACO flux, it looks like a new penny. That's why plumbers use it. Been using LACO since the early seventies.

[Bill Dufour]

Do not get discouraged if the soldering is harder then you remember . It is due to the new improved solder which does not flow as well, needs more heat, and has a narrower range before the flux burns.
Bil lD

[Ron Citerone]

The new solders are different for sure.

Also a teacher once said to me the three most important things for soldering is "Clean, clean and clean."

[Frank Pratt]

It's because the solder no longer contains lead.

[Wade Lippman]

I did 14 joints, no leaks. Very proud.
I did all three joints in a T and it worked.

When I was cleaning up I found some old lead solder. Good think I didn't see it earlier or I might have wimped out.

[Tom M King]

Good job. Of course it worked on the T. I don't know why anyone would want to do it any other way, unless there was some specific reason to.

[Ole Anderson]

Soldering a long run of fittings successfully gives you a real feeling of accomplishment. Having to pull a run apart because one leaks really sucks the life of of the accomplishment. For the occasional copper fitting, or one where it is nearly impossible to get the pipe dry, I now go the Sharkbite route.