My last pipe soldering question for a while

I finally did the installation I have asked a bunch of questions about. It involved putting some Ts in the main water line.

One of the joints had a tiny leak, maybe a cup an hour. Reheating it, needless to say, didn't help; so I pulled it apart, recleaned, refluxed and resoldered. It is fine now. But I have some questions for future reference.

2) I have some plastic stretch tape that claims it stops leaks. If I applied it with the water off, would it have stopped the leak; had I not been able to take it apart? If not, would any product?

Thanks

I don't plan on doing anymore plumbing in the new future. Oh, not quite true; I have to replace the kitchen faucet. Hmm.

Never ignore warning signs when they are given to you.

I installed a water softener with all sweat soldered fittings. Apparently I didn't seat one of the fittings all the way, or maybe it was a cold solder joint. The joint never leaked, but it let go one night and fortunately I was home to hear the water gushing out into the garage. Had we been away on vacation, it would have flooded our home.

Ah, something new to worry about! What is "not properly seated"? Only 1/4" of the way into a 3/4" deep joint? My "system" is to make sure that all but the fringe of the 1" that I clean is inside the joint. As long as I do that, the joint must be seated properly; right?

What is a cold solder joint? If the solder melts on the pipe and flows in, it must be hot soldered; no?

If the solder melts and flows it is hot, the problem is the pipe may not be hot and it may not be properly bonded to the cold pipe. Watch what happens when a drip of solder lands on a cold pipe sometime. It just forms a ball and rolls off. That is why you heat the pipe not the solder and wick the solder into the joint. It will not melt or wick if the pipe\fitting is not hot.

But if it does wick, then it is hot; right? (That is what I meant by melting on the pipe and flowing in.)

You've got a good system. In my case I think the most likely cause of the failure was a shallow joint (maybe 1/2" or so) combined with a soldering job that was weakened by some movement while the solder was cooling. I'm speculating here, but I think there was a partial fracture of the solder connection and that over time (perhaps with some vibration from the recycling of the water softener) the joint broke loose.

Not always, but I most of the time anyway.

A cold solder joint means that the copper is coated by the solder, but it never actually combined with it. Usually caused by dirt/oxide on the copper or movement during cooling.

A proper solder joint actually blends the copper and solder together into an alloy.

Left out one vital step...clean the inside of the fitting.

If you do the above steps, it be fine. As I noted before, it's like the old question--"Do you know how to get to Carnegie Hall?"

I was taught to:

Are your telling me that is not always true? Is there anything else that needs to be done, or any way to distinquish between good and bad joints?

I am not being argumentative; I just want to get it right.

Movement during cooling? My understanding is that the solder is either liquid (when it can be moved) or solid (where it can't be moved). The transformation was quick enough that movement was not an issue; at least in small pipe not exposed to high forces. If any of the solder is solid enough to be be damaged by movement, it has already become strong enough to prevent that movement.

Am I misinformed?

One where the solder has formed crystals.

No. Movement in the joint while cooling is the most common cause. The solder doesn't setup as a single cohesive metal, but rather as crumbly material, which looks "cold" compared to a good smooth shiny joint.

Not fully preparing the surfaces to be soldered is another cause, since it keeps the solder from flowing everywhere.

The trick to soldering is to get a complete sheet of solder to melt and reform at the same time, so it is solid.

You got it right. Following those instructions it should work, but most of us, well at least me, are not perfect and even when I think everything has gone well, sometimes it did not (as you noted "assuming it did not leak under pressure.") Maybe not clean enough, not quite enough heat due to moisture in the pipe or working too fast etc. Frankly I seldom if ever have a problem when I follow those procedures. It is not all that hard.

Yes.

and the fitting

and the fitting

This is wrong: heat the *fitting*, not the pipe. The idea is that the fitting will expand when heated, and contract as it cools, tightening the joint.

Opposite side of the *joint*, to be precise.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

Yes, you are. The transition from liquid to solid is neither as rapid nor as clear-cut as you think. Alloys generally don't have a crisp melting or freezing point; instead, they liquefy or solidify over a range of several degrees. There is also a range of temperatures below the melting point in which the metal is plastic, that is, easily deformable. If a solder joint is mechanically stressed before the solder has cooled below the plasticity temperature range, it will be considerably weakened and may fail.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

I've always heated both the fitting and the pipe, gently and evenly. Testing the tip of solder on the junction every so often until it melts then soldering the connection.

Should i not be heating the pipe at all? I thought it was best if both were at temp.

Charles Bishop wrote: ...

Taught us to heat the pipe the fitting, initially around it if