How do I "fix" a bad sweat (solder) joint?

Question

I tried soldering some 1/2" copper (to make something like this) and some of my joints are horrible.

I tested it with water and some of the joints leak.

1. What is the best way to fix the joints?

2. What is a quick and easy way that will work?

These pipes do not need to much pressure. (they are fed fluid from a holding tank into a float valve - the tank is about 100 gallons and sits about 3 feet above the float valve)

I cleaned them and fluxed them before attaching but since the joints are so close together I am not sure if I burned off the flux in the unsoldered joints before I got to them.

I might also have a torch that is too hot?

Answer 1

Just heat the joint up with your torch, once the solder starts to melt use Channel locks to pull the fittings apart. Once the joint is apart, wipe as much old solder off as you can with a rag. Now you can start over. Clean, Flux, solder.

You should not be applying flux to joints you are not working on, take each joint one at a time. If the joints are all close to each other, try doing the joints out of order. Solder one joint, then move to a joint further away, then back to a joint near the first, etc. This should allow some of the heat to dissipate, and reduce the chances of overheating the joints.

Don't forget to wipe excess solder off the joint before it cools using a damp rag, nothings worse than an ugly joint (except maybe a leaky joint). And don't forget, soldering pipes is an art. And like most things, it takes lots of practice to get good at it.

Answer 2

Lot of bad info in this, to the point that it's comical.

Don't need a MAP gas torch. Propane is plenty hot for normal sized copper piping (up to 3" or so).

Wiping a rag on the fitting isn't needed, all that does is smear the solder that's hanging on the outside of the fitting around. Looks better, but it doesn't do anything else.

Don't use too much flux. It will get into valves or glob up in the pipe, stay there and erode a hole after a while. Just a skim coat over the pipe or fitting (either or) is plenty.

If you are getting a green flame, that's too hot.

Answer 3

Because all of these joints are really close together, you will probably have to redo them all. At a minimum you need to heat up the leaking joints and pull them apart, and then re-solder them.

I doubt you are making them too hot, it is too hot if you get the copper glowing orange/red or if the pipe or fittings are deforming.

I use a MAPP torch and my process is something like this.

1. Clean the pipe and fitting.
2. Go crazy with the flux, flux is your friend that "sucks" the solder into the joint. Do not skimp on the flux.
3. Heat up the fitting, when the flame turns green it is hot enough.
4. Quickly add the solder all the way around the fitting. It should melt immediately and get sucked into the joint.

I am not great at soldering so I find it really helpful to have someone else help. One person can use the torch and other uses the solder. That way you can start soldering right when the torch is off of the pipe.

Answer 4

The best way to remove solder is by using a heatgun thats designed for that specific purpose. It is essentially a blowdryer that gets hot enough to melt/soften the solder.

Answer 5

With either propane or MAPP gas it is actually very easy to get the joint too hot. You can actually boil the solder out of the fitting or into the pipe depending on your torch placement. Not so much with larger piping, but with 1/2" it is easy to do it. You should only use about 1/2" to 3/4" of solder to make a joint on that size; don't add more or you could just fill the pipe. Keep a dry rag to knock off excess solder and a wet rag to cool and clean the joint. Flux causes oxidation (turns green). Don't worry about burning off flux: it will take unless it's too hot. There should only be slight discoloration; if there is more then there is too much heat. So as soon as the solder melts, pull your torch away a few inches but make sure to start solder at the bottom and work up, and move the torch around evenly.

Answer 6

1. MAAP GAS. Pros use this. Even if you are soldering a couple of joints it is worth the price otherwise you are handicapping yourself and will end up paying to get a pro out (who will use a MAAP gas torch.) Once you use it you will understand and be upset you didn't get it earlier. I had used propane for years to "save" money, I wish I hadn't "saved" that money as I had to redo some joints / take a lot of extra time.

2. Dry. If there is any water you will fail. Use a small tube to suck the water out if there is any water left. Such as those small irrigation drip lines or a fish tank air line.

3. Clean with wire brush or sandpaper / apply flux. If it is not clean you will fail.

4. Once you have the fittings put together, tap the fitting with the solder as you heat. You want to heat the outside fitting, DO heat the pipe going into the fitting too - both mating pipes have to be hot enough to have the solder melt when it contacts either side of the pipe. of course touch your solder against the inner pipe along the seam with the outer pipe. Move the heat around the fitting, don't hold it in one place. Obviously don't put the flame directly on the solder or you will melt it. As soon as the fitting sucks in the solder, stop heat and move the solder around the joint quickly.

Answer 7

Since you have leaking joints, heating them up and adding more solder will not work because the new solder won’t get sucked into the joint due to a lack of flux. Sorry to say, each bad joint will have to be removed. I would use a MAPP gas torch, as it burns hotter than propane, which will get the job done quicker.

Once removed, look into each copper pipe and see if there is anything present that would cause the joint to fail. If there is take remedial action to solve the problem.

You mentioned the pipes are close together. This likely is why the joints failed. The first one went fine. For the second one, you heated the pipe and the heat was sufficient to melt or soften the solder on the first joint. As someone said earlier start soldering the joints furthest away from each other. The problem is at some time you have to sweat a joint close to another one. In this case, take a cold wet rag and encircle the joint that was already done. This should keep the joint cool enough. If you’re still worried, use the propane torch, which is cooler than a MAPP gas torch.

It goes without saying that the end of the copper pipe and the inside of the joint have to be squeaky.clean.

Answer 8

I am no pro at this stuff, but I have found that for my amateur stuff, I have much better luck with the liquid flux than the paste. With the liquid, you don't have to worry about getting dirt back into the mix..

Answer 9

I just fixed two bad joints, didn't disassemble them any of that nonsense. I used map/pro mix. Before anything got heated, I washed the outside of the pipes with warm soapy (DAWN)water to get the old flux etc...off. I let it dry. I heated the coupling that was leaking on both joints and worked my way around both endson both sides. Then i fluxed both joints all the way around quite liberally, hit both seams again with the torch, and followed the torch with an inch of solder each. waited for it to cool.....and whadda-ya-know? batta-bing! batta-bang!