My last pipe soldering question for a while

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wrote:

63/37 solder solidifies almost instantly.
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"almost instantly" isn't "instantly".
Try this experiment: solder a pipe joint while rotating the fittings. The joint edges won't be shiny, and there's an extremely good chance it will leak under pressure.
Solder tends to harden via crystalization. If moved during the critical period, the crystals will literally rotate, and the final solidification will be filled with voids, and be much weaker.
This is an issue with electronics soldering too.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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I was taught to: 1) Clean the pipe 2) Flux the pipe 3) Heat the pipe 4) Let the solder melt by contact with the opposite side of the pipe and flow into the joint. If it wicks around and flows out the opposite side from where it was melted, it was a good joint; assuming it did not leak under pressure.
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.
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toller wrote:

Left out one vital step...clean the inside of the fitting.
If you do the above steps, it <will> be fine. As I noted before, it's like the old question--"Do you know how to get to Carnegie Hall?"
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toller wrote:

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.
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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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?
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snipped-for-privacy@milmac.com (Doug Miller) wrote:

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

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Charles Bishop wrote: ...

Taught us to heat the pipe <through> the fitting, initially around it if 3/4" or larger to speed things up.
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If you want to be perfectly anal about it, the best way is to heat the fitting, and then apply solder to the _pipe_, on the other side of the joint, and not touch the solder to the edge of the fitting until it starts to flow against the pipe.
What this does is force you to be applying solder against the coolest part of the joint. Once _that_ is up to temperature, you're guaranteed that the rest of the joint is up to temperature.
It matters more to pros, because they're often using acetylene or MAP torches, which heat the joint much faster than the gentle roasting of a propane torch, and temperature differences can be rather high.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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snipped-for-privacy@earthlink.netttt (Charles Bishop) wrote:

You should apply heat only to the fitting; the pipe will get hot enough anyway through contact with the fitting. If the pipe is heated directly, it can expand far enough to prevent sufficient solder from flowing into the joint, producing a weak joint.
-- 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?
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Doug Miller wrote:

A few opinions on sweating pipes, I do this for a living. Even went to school for it. Use the hottest torch you can get, my favorite for soft solder is a Turbo Torch using Mapp gas. Then use the hottest part of the flame, in this case about 1/2" past the inner cone. You will do less damage to the surrounding area with a hot torch. Get in there get it hot and get out. Clean everything including the solder. Apply a paste flux sparingly to the outside of the pipe, first 1/8" inside of the fitting, and a little on the solder. Secure the pipe to avoid movement. Rule of thumb, with normal 1/8" solder you will use the same length of solder as the circumference of the pipe. Make a bend in the solder at that point. Protect any heat sensitive parts with wet rags. Preheat the pipe concentrating at edge of the fitting and keep the torch moving. When the pipe is hot enough to melt the solder move the torch on too the fitting. That is the big secret, solder will flow towards the heat. This is especially important on vertical joints. Practice on some scrap pipe, with a little technique you can literally pump solder uphill through the joint and into the inside of the pipe. I test all my soft joints at 200 psi and my silver (solder) braze ones at 400 psi, I don't have leaks. Dave
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On Thu, 17 Feb 2005 10:59:03 -0700, Dave Morrison

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Why sparingly? Why only the first 1/8" of the fitting.

That seems reasonable. I simply let solder melt in until it starts coming out the other side. While maybe a little wasteful and homely with the resulting globs; it ought to be adequate. No?

That is contrary to everything I have ever heard, ie, that the pipe should not be directly heated; only the fitting should be heated.
Do you keept the torch on the fitting until you are done?
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toller wrote:

You simply don't need more. As to the first 1/8", it minimizes interior contamination, if it doesn't matter on your job smear away :-)

Danger here is excess solder getting inside pipe. I have seen enough solder build up inside joints to severely restrict flow, and globs of solder breaking loose latter and fouling valves. A quick wipe with a damp cloth will take care of that exterior glob and give you a pro style joint. I have seen claims that a wiped joint is stronger than a drippy one but have no personal knowledge.

That pipe inside must be up to temp, both to activate the flux and allow the solder to amalgamate with the copper. That lack of amalgamation is the cause of those good looking joints that leak. Preheating the pipe first is the only way you can be sure that the interior will be up to temp.

No, it's a balancing act. Enough heat that all the solder will melt and not so much that it gets pumped in to the interior of the pipe.

Dave
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You are absolutely correct; fortunately I just misspoke rather than misunderstood; I meant fitting in all contexts.
Interestingly, my OP referred to the first soldering of the joint failing. When I pulled it apart there was no solder on the top of the fitting; yet it was bright and the scratches from the brush were still visible. The pipe on the other hand was completely covered with solder. All I can figure is that I didn't put enough flux on it, but even if I didn't, shouldn't enough flux have rubbed off from pipe to have worked? Apparently not. Anyhow, I started using twice as much flux.
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toller wrote:

I can remember once when I put in a water heater using CPVC and turned the water back on. Everything was looking good when a little drop formed under a fitting. I touched it and it gave way. I had totally missed that fitting, no cleaner no solvent. :-)
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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Could be worse... this guy I used to know re-plumbed his kitchen, and didn't even *know* he was supposed to cement the pipes into the fittings. I heard the story from his wife; I guess there was quite a fountain in the crawlspace when he turned the pressure back on...
-- 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?
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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.
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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?
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toller wrote:

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.
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