I have a question relating to analyzing a soldered copper joint. I know I read something fairly recently about sawing a soldered joint in half and then flattening each half & separating the soldered pieces to see if the solder completely filled the joint. The writing also had explanations as to why there would be unsoldered spots, gaps, black parts in solder, etc.
I thought it was on this forum but, have not been able to find it. Does anyone know where this type of information could be found.
Just curious because after the plumber was done there were a few spare 90's & tees left that I had bought for him as extras that he didn't take. So I figured what the heck and tried sweating numerous joints. Then cut them in half & separated them. Some had spots with no solder. One reason I think some of the spots happened is because I tried squeezing the joints like the plumber did so I do not think solder flowed to those two tight points (since noticing that the two unsoldered spots were across from each other. After doing this I am glad I had an experienced plumber do the house. I guess one never really knows if the soldered completely filled a joint. Except for maybe a joint or very small repair in the basement or open area I will stick to my profession and not try to become a DIY plumber. Will probably still generate some questions though. I sincerely hope this is the last house I remodel and it has definitely make me realize an appreciation for the profession.
There"s no great mystery about sweating a good joint. There are of course some principals that you must adhere to, but these are not really difficult. First, there must be absolutely no water in the pipe. Even water at a distance will be drawn by the heat an make a good joint impossible. Next, the pipe should be cut square and deburred inside and out. This will also clean the outside of the pipe. This should be done immediately prior to soldering, not a day or two ahead. Now clean the inside of the fitting with a stiff brush or emery cloth on a stick. Apply flux to the fitting and pipe then insert the pipe into the fitting. Apply heat to the fitting. Do not ever just try to melt the solder with the flame. Move the torch around the joint so as to apply the heat as evenly as possible. Hold the solder on the seam of the joint away from the flame until it begins to flow. Remove the flame and move the solder all the way around the joint. Do not move the joint until it is cool, but you can take a damp cloth and wipe the burned flux and excess solder while the joint is still hot. Remember it is very hot, so use care. If you will do all of those things, you can be assured that you have a good joint.
Is it important to wipe a solder joint. I always do, but my plumper I hire for big stuff rarely if ever does.
I'm a DIYer, not a pro
By wiping the solder joint with a rag you get a chance to see if you have missed something, also by not wiping the excess fux off you can end up with a green corrosve ring around the joint; in a moist environment you can end up with greenish trees growing around the joints. It also makes the job look professional.
I wear an all-cotton string knit glove on my left hand ( I'm right-handed ) when soldering. The cotton is enough to insulate against brief contact with a hot copper pipe, and it's easy to quickly wipe joints down with a finger. Don't get the glove wet if you can help it, a wet glove will conduct the heat straight to your skin. I always wipe the solder away from me.
I tried leather, but I could not feel the pipe very well. The weave of the cotton seemed to have enough thickness to insulate, but it's still flexible. Don't get the kind with rubber dots, they will melt to the pipe. I'm sure everybody has their preferred method.
To test a solder joint, all you have to do is heat it and pull it apart. If there are bad areas you will see them on the tubing and/or inside the fitting. No need to saw anything apart.
That "erosion" you see would be typical of a hot water circulation system with a pump creating excessive velocity in the pipe, causing turbulence downstream of turns/elbows in the pipe.