View Full Version : soldering giving me problems ...

07-29-2012, 06:50 PM
I've soldered a few small jobs in the past but now am having problems.

I feel I am missing something basic that did not come into play on my previous work.
I'm assembling 3/4 and 1/2 copper supply pipes for a new bathroom.

Maybe someone can clarify and/or answer some of these questions:

1) I suspect the problem has something to do with even heating of the pipe.
- Is there an optimal distance to hold the torch (propane) off the pipe and joint?
- I am heating the pipe first and then the joint. Is it the reverse? Does it matter?
- There seems to be a small window of time that the pipe is hot enough to melt the solder but I still get solder running around a horizontal joint and dripping out the bottom without being carried into the joint (I'm only using a thin coat of flux).

2) I am trying to assemble the major sections of pipe on a sheet of plywood. This helps keep a long assembly of pipe with angles square.
- Should I be putting something under the pipe to separate it from the wood?

3) If I have several joints in close proximity should I place and solder each one separately or assemble the group and move from one to the next?

4) My understanding is that the soldering process works by heating the pipe so it melts the solder and once liquified it is draw by capillary action into the joint.
- Is there something else going on?

Yes ... I'm feeling like a beginner.

Thank you.

Tom Sawyer
07-29-2012, 06:55 PM
Clean clean and clean some more. Inside the fitting, outside the pipe. Ream the inside of the pipe. Flux outside the pipe and inside the fitting. A light coat, not a snot ball. Assemble the joint. Heat the fitting not the pipe. when flux bubbles apply solder to the joint. 1/2" fittings need a 1/2" of solder, 3/4 -3/4 and so on until you get to 1-1/4" and larger which take more solder. Let cool naturally. Wipe the excess flux off the joint. If the fitting turns black when heating it's too hot. Disassemble it, re-clean it and start over.

07-29-2012, 07:10 PM
Heat the pipe too. It is as much of the sweat joint as the fitting is. This is very important when sweating larger copper pipe assemblies. I was trained to move the torch in a figure 8 pattern from fitting to pipe for even heating.

07-29-2012, 07:34 PM
The fitting is the heavier (usually) component, so normally, if you heat it, when it's hot enough (since it's in contact with the pipe), the pipe will be hot enough as well.

Tom Sawyer
07-29-2012, 07:46 PM
Never heat the pipe. Size the flame to the size of the work and there is no need to heat the pipe or use a figure 8 pattern. Apply the flame to the center of the fitting and move it to where the flame wraps around the fitting.

07-29-2012, 09:24 PM
Laying the pipe on plywood and soldering it there is a mistake.
If you want to "prefab" the pipe, at least block it off the ground. Heating the fitting and pipe evenly is very important. That means getting heat to all sides of the fitting.

07-30-2012, 01:04 AM
Never heat the pipe. Size the flame to the size of the work and there is no need to heat the pipe or use a figure 8 pattern. Apply the flame to the center of the fitting and move it to where the flame wraps around the fitting.

If I'm working with 4" copper, where will I get a torch that big?

07-30-2012, 10:40 AM
If I'm working with 4" copper, where will I get a torch that big?
You can afford 4" copper?

Obviously, what works at one scale doesn't necessarily work at another...

07-30-2012, 10:54 AM
I work at a university. Occasionally we work on water mains and sump pump piping.

07-30-2012, 11:16 AM
If you are working 1" and less, then heating the fitting usually is adequate to also bring the pipe up to temp. Nothing wrong with briefly hitting the pipe with the flame. On the flame, there is an inner, very bright blue area. The end of that bright blue is the hottest part of the flame.

A pipe of say 3/4" size should be at temp in less than a minute. If you are heating longer , then you may burn the flux.

07-30-2012, 12:54 PM
Do not direct your flame into the face of the fitting. Do not burn your flux...(over heating)

Tom Sawyer
07-30-2012, 01:43 PM
4" copper, it's time to get out either the Turbo T8 tip or go with acetylene.

07-30-2012, 04:48 PM
You mentioned your using 1/2 and 3/4 then later on 4" pipe? if your using 4" copper waste lines then you'll need an acetylene torch for the 4". Copper is the second best conductor of electricity and one of the best conductors of heat. If it is the 4" pipe giving you problems it is because a propane cannot heat such a large area and you may get cold solder joints (leaks). On a 1/2 and 3/4 pipe your leaving the torch on the pipe too long and over heating it thereby allowing the solder to remain a liquid and run out if the joint.

How to solder a joint, as mention earlier is clean copper at all joints. You must use flux on all joints and a just smear is good enough. What flux does as it is heated it actually cleans the copper and prevents the copper from oxidizing, therefore do not over heat the joint, Solder travels from cold to hot, as the pipe gets to temp apply the solder furthest from the flame but the flame should be removed almost immediately. Once you see the bead of solder to go around the pipe pull the solder & heat away.

When soldering on a vertical section of pipe, always start at the lowest connections. Heat also travel up the pipe faster than it travels down. If you start at the top and work down, the heat will rise and kept the connection soft and the solder may run out of the joint above.

For info on solder go to http://en.wikipedia.org/wiki/Solder

07-31-2012, 01:28 AM

I personally don't have a problem with copper but this might be of some help. There are some videos here. They have a training program, they will come to you and do a hands on seminar. Not sure if it costs anything. There is a product called COOL GEL. It is a great aid for doing this kind of work too.


You can spray this stuff on cardboard and put a turbo torch to it with mapp gas and it won't burn. AWESOME PRODUCT. ACE sells something similar.

07-31-2012, 07:03 AM
quote; Heat the pipe too

The solder flows TO the hottest area of the joint so you heat the fitting where the end of the pipe is. As for 4" copper, you borrow my 4 burner staghorn acetylene tip, (I also have a smaller one for 2" copper).

04-19-2013, 05:25 PM
After several horrific problems with soldering copper joints over my head, getting responses from this forum and searching the internet in general and You Tube specifically I modified my technic and those changes seem to have resolved my problem.

All the 7 joints were over my head and in fairly tight places under the floor reached from my crawl space.

I did most of these before but was not as scrupulous.

1) Clean the inside of the fitting and the outside of the pipe until it is shiny with no specks.
2) Make sure there is no water in the pipe in the area of the fitting. Heat the pipe with the torch if need be.
3) Support the pipe so the fitting and pipes are eye sight straight.
4) Wipe the inside of the fitting and outside of the pipe ends with a clean dry cloth and do not touch them with the hands again.
5) Flux the inside of the fitting and the ends of the pipe with a clean brush and assemble fitting.
6) Get comfortable so it is possible to move around the fitting as it is heated and soldered before lighting the torch by moving other tools back.
7) Heat the fitting only blowing heat back to the pipe and moving it side to side and angling as best possible to have flame blow over the top and sides of the fitting. I notice the flame will actually bend some.
8) Bend the end of the solder 1" and then bow it to reach around the fitting seam and keep your hand out of the flame.
9) Watch for the Flux to fizz and then repeatedly test the end of the solder to the fitting seam to see if it melts.
10) Feed solder into the top and sweep it along each side. The reason I bend the solder end 1" is that I find on 3/4" pipe it takes about 3/4" of solder to fill the joint and an 1" allows some to fill the joint and drip out the bottom. I guess 3/4" would work for 1/2" pipe.
11) Wipe the joint clean of Flux and wait 30 minutes for the pipe to cool before pressurizing the pipe.

Celebrate ...

Thank you for everyones input.

04-20-2013, 07:15 AM
#5 should be done after step #1, and skip step #4. Don't "measure" the solder, just use whatever you have to in order to make a good joint. "30 minutes" is about 27 more than you need to cool the joint.