Sweating 1 1/4 inch copper

I’ve been sweating 1/2" and 3/4" pipes for years, but working with 1 1/4" on my furnace (boiler) has been a pain. Lots of problems with horizontal joints getting the solder to suck into the joint on the bottom. I only have one more section to do, and I’m cutting out a large section of pipe so one side will be a vertical ‘gravity fed’ joint. But the other side will have to be done in place, on a horizontal pipe.

I’m using MAPP gas, common handyman torch, paste flux. Found some higher grade solder at the hardware store, better than than usual mega-store brand. I heat the joint all around for a while before focusing on one spot to start the soldering. Applying solder about 90 degrees from where the flame is focused. Is it just me, or was lead solder a lot better?

Anyway, any advice for that horizontal joint, or larger pipes in general?

Also, I should have asked this a year ago, what’s the best way to join copper to iron?

The torch you are using is the main issue. The typical handyman torches have a head sized for 1/2-1 inch pipe. They simply don’t offer a large enough flame to keep bigger joints evenly heated. I use a turbo torch set up and have heads to go up to 8inch copper.

It isn’t you can’t do larger joints with an undersized torch it is just harder. Frequently moving the torch completely around the joint will help. The whole joint needs to be similar temperature for it to take solder correctly. Use lots of flux.

Lead solder was better in a lot of ways, including taste! Functionally it is slightly better but it isn’t a lot better.

As to copper to iron pipe? Threaded fittings. Beyond that you’ll have to consult a welder.

Thanks. I thought flame size might be an issue. I have another torch somewhere, if I can find it, and I just picked up an extra bottle of MAPP, so maybe I can hit it with 2 torches and get someone to feed the solder for me.

And right after I posted I realized I didn’t have to do that vertical joint at all. I’m disconnecting the pipe at the compression fitting on the circulator. I don’t know why I even considered cutting the pipe there. But I’ll still have to do that horizonatal joint to close everything up.

The copper iron transitions caused these problems. At the bottom of the boiler for the water return there was a continuous drip, and the same on one side of an iron tee that came with the expansion tank. The only fittings I could find were copper female threaded to join to an iron nipple. It seems like poor design because the copper on the outside will expand more than the iron when hot. This time I used pipe joint-tape-pipe joint on the iron nipple for the return, and it seems to be leak free. Now I have to drain the system, and I’m taking the iron tee out and replacing with copper.

I’ve never had issues with copper-iron/and or steel. I can understand your logic but in my experience the thermal expansion of fittings isn’t enough to cause a leak. I’m not a heating guy however so that end of things may be different enough that they experience that issue.

Copper to galvanized steel however is a mistake many people make with heating systems and it will cause issues.

Connecting disimiluar metals can cause problems. Copper and Iron do not mix unless a dielectric union is used.

Their is a kit available for soldering dis-similar metals.
It’s usually available at Air Conditioning parts warehouses, or perhaps Google it.

When sweat soldering larger dia copper pipes, ya rap on the pipe as you solder while still hot and feeding the solder and it allows the solder to flow around the fluxed areas better.

Use a high quality silver solder, with flux.

When I saw the question, the first thing I thought is that you need to go to MAPP. But I see you are already using it. I have had trouble getting hot enough due to the altitude I live at. Propane is near impossible.

I will probably get slapped for this, but they use to make a solder paste. It would be applied like flux (finely ground solder is pre-mixed with flux) in the fitting and then heated. I recall that it worked quite well. Anyone ever use that?

Perhaps I mis-remember. I can’t seem to find it online except for printed circuit applications.

Thanks everyone. I’ll try **Lee Vining **'s idea of rapping on the pipe when I close up that last joint.

The copper to iron transition I replaced seems to be tight, so I won’t go further with that. The other leaky one on the iron tee is coming out and being replaced with all copper. The circulator has compression fittings, all iron, I keep looking for a copper to iron equivalent, with a dielectric gasket, but no luck so far. But I should be done soon, and once I have this closed up, I don’t intend to change anything for a while.

Someone had a poll on what kind of community the SDMB is. My answer would be ‘A great one’. Thanks again. - TriP