When will my sweat joints leak?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jok, Jan 29, 2012.

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  1. Tom Sawyer

    Tom Sawyer In the Trades

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    I recall somewhere there is something that tells you the strength of a soldered joint but for the life of me I can't find it anymore.
     
  2. Hackney plumbing

    Hackney plumbing Homeowner

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    It doesn't state the strength of a solder joint I made that was suppose to be a complete failure. Now would it?

    Did you even read the thread?

    Thats like telling the inspector...."I dont need to test my pipe because the manufacture already tested it" LOL
     
  3. Tom Sawyer

    Tom Sawyer In the Trades

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    What exactly is the point of all 6 pages of this though? The OP was concerned about the integrity of his soldered joints and since nobody is required to test water supply lines past 100psi it would seem that his concerns were laid to rest. Oh yes, then we got all bogged down in the dynamics of soldering a closed pipe which again, who cares? Like I said, sometimes you can and sometimes you can't but most of are going to err on the side of caution and open a valve if possible. So what does testing your cap to 6500psi prove? So I suppose we can all give you a pat on the back for your efforts but in the end......what a waste of time LOL don't you have service calls to do?
     
  4. Hackney plumbing

    Hackney plumbing Homeowner

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    The point was to correct incorrect information. I corrected it.

    No ones all "bogged down" unless they have trouble reading and understanding.

    Who cares? Seems like a few of us do,if you dont then why bother?

    Again,get it right.....I tested the cap to 3800 psi at which time the copper pipe itself failed. It proved the joint was stronger than the pipe itself.

    Why are you so concerend with what I do with my time?
     
  5. dlarrivee

    dlarrivee New Member

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    Hey Tom, if you're not a curious person why are you even on this forum in the first place?
     
  6. ballvalve

    ballvalve General Engineering Contractor

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    Yeah, I think Tom Sawyer needs to go swing a cat by its tail. Probably embarassed to find a plumber that is curious about what he does daily and takes the time to actually TEST it.
     
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Somewhere in all of this, was the original implication that soldering a closed piping system COULD cause a joint to fail, not that it would. At least several of the people who have responded have indicated that they've had a failed joint when it was closed, and not had one when it wasn't. My original point is and was: (at least try) to leave the system open when soldering that last joint. If your technique is good, and nothing weird is going on, you're pretty much guaranteed a good joint. If it's closed, albeit maybe a drop of moisture, a really tight fitting, or whatever, you MIGHT have a problem that wouldn't occur if there was an easy path to relieve any potential pressure increase. The air DOES expand when things are heated, and if it can't go somewhere, it will go to to the weakest point, and that could be the liquid in the joint. It doesn't take much of any pressure differential for a bubble to move through a liquid. As long as things have stabilized, you're golden, otherwise, you're not.

    It's really annoying when people take a possibility and read it as a certainty and go off on a tangent. Life is about reducing risks when you can, and this is an easy one to practice. I'm not losing any sleep over it, and the obsession of others seems excessive. It comes down to the fact, not theory, that heated air expands, and that increase will either increase the pressure, or leak out somewhere as, for practical purposes at the pressures involved, the pipe is essentially a rigid body. You may or may not be affected by it, but it is easy to avoid.
     
  8. Hackney plumbing

    Hackney plumbing Homeowner

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    Here you say MUST

    In this post you say COULD

    Whats really annoying is when people act like they didn't say something when they did. Even more annoying when its in print.

    Whats the big deal about running a few test? Why do you think thats obsessive?
     
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    It has to leak somewhere, so given a choice, I'd much prefer it to be controlled, so yes, you must leave some path open. That is goes through the joint is the problematic situation, and to avoid potential problems, yes, you must leave an end open.

    One instance does not make a valid scientific test...take something like when you have a coupling, the whole coupling is hot enough to melt the solder in most cases, and because it is bigger, you're heating more of it. Same thing with potentially a valve body. The OD of the pipe is supposed to be held to fairly tight tolerances, but with a bunch of the imported stuff, match up an oversized pipe with an undersized fitting, and you have a potential problem.

    If you want to avoid the possibility, you must leave an end open, and I'd rather that not be the fitting you're trying to solder because some air WILL move through that fitting if there's no other place for it to go. If there happens to be liquid solder there at the time, then you may have a problem. Eliminate the possibility, and you don't.

    Let's give this a rest.
     
    Last edited: Feb 18, 2012
  10. Hackney plumbing

    Hackney plumbing Homeowner

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    If the joint is too tight then it is too tight.

    Opening the pipe to the atmosphere doesn't correct that the fitting is tight and then you have an improper joint. You should have .002-.005" uniform space for capillary action to best work. Any closer than that the filler metal is not of sufficient thickness.

    To avoid this make sure your have proper joint tolerances.

    I enjoy discussing the subject and really dont see a need to give it a rest. Discussion is what I'm here for.
     
  11. Tom Sawyer

    Tom Sawyer In the Trades

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    And the real point of all this is that when you ask the right questions, you get the right answers.

    BallValve - I do so enjoy cat swinging from time to time and I'm pretty sure this one's all swung out.
     
  12. Hammerlane

    Hammerlane Member

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    Good posts and comments. Cudos to Hackney for showing his video. I guess what is proves is an ongoing debate.
     
    Last edited: Feb 19, 2012
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    What it proved was that the air expanded, the pressure temporarily rose, leaked through the fitting, and was apparantly stable when the solder was added. Had the timing changed slightly, that air may have cooled a tunnel through the solder joint and it would have leaked. Putting on your seatbelt won't prevent an accident happening, but if the planets align, and you do hit something, the physics involved it can save you. Open the pipe to the atmosphere does the same thing - it provides a safety net for something that does happen...the air does expand, pressure builds, it tries and generally does escape somewhere. How much it expands depends on your technique, hot hot you make the joint/pipe, and how tight the joint is, how much flux is there, when the solder is applied, and the list goes on. A DIY'er tends to end up heating a joint longer, the heat conducts, warming more of an area and potentially expanding a larger volume of air.

    This was never a statement that it would create a bad joint, but that it could. Depends on technique, skill, materials, luck, etc. Open the pipe to the atmosphere, and it can't happen, at least from that situation.
     
  14. Hackney plumbing

    Hackney plumbing Homeowner

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    So soldering has a certian amount of luck to it now? LOL Speak for yourself. Get your joint tolerances within specs and its not a problem. Its all part of the knowledge itt takes to do the job correctly 100% of the time. I assure you its not luck.
     
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    A DIY'er needs all the help he can get...following this eliminates one easily avoided pitfall.
     
  16. Hackney plumbing

    Hackney plumbing Homeowner

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    You still do not understand the point. If the joint tolerance is too tight the pressure will build.....right? Ok opening the pipe to atmospehre will correct any pressure build up but it will not correct the joints tolerance. Its too tight and the joint is improper.

    Too much flux and the joint is improper.

    Too much heat the joint is improper.

    Your "work around" is only enabling bad joints to be made. Get the joint tolerance correct and dont worry about opening anything to atmospheric pressure.

    Do things the right way.
     
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    And, you're missing my point...a DIY'er needs all the help he can get. Experience is likely not one of his attributes. An easily applied technique can remove one of the pitfalls to his ultimate success. It's easy to do, and works, and eliminates a potential pitfall.

    Feel free to do whatever you wish.
     
  18. Hackney plumbing

    Hackney plumbing Homeowner

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    So you idea of a good solder joint for a DIY'r is one that doesn't leak. I understand your logic now. while the joint may not leak it is a weak joint. Not enough filler metal was used......this creates a thin joint. An improper joint.

    Its not always easy to do and it doesn't eliminate if the joints too tight.

    Air pressure is not the problem anyway its moisture in the film layer of the copper flashing to steam. If the joint was air tight the air couldn't blow your solder out because it cant get out...thats how it built pressure. Steam on the other hand can and will build substantial pressure and it will escape.

    Steam and over heating is 99% of most peoples soldering problems.....not air pressure rise in the tube.
     
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Let's review a little...It started when I said when making the last connection, you must have an opening to the atmosphere. I didn't say you would have a bad connection, but the implication was that you could.

    Then, a demonstation was made proving my point...heating the last fitting on a closed system raised the pressure as the heated air expanded pushing through the fitting to the only path or opening it had. Until the whole system came into equilibrium, the air was expanding and moving through the fitting - the fact that the pressure peaked, broke through and then stayed constant does not mean that air stopped moving through, only that the pressure couldn't rise as it expanded - i.e., it was being relieved. Depending on when that occurs, will depend on whether there's enough pressure to blow through the solder to compromise the joint. Air in a closed body will increase pressure at about 0.1#/degree (this will vary based on what you start with - more at sea level, less at say Denver where you'r nearly a mile up). I don't know how much pressure a liquid solder joint can withstand, but as a joint is being heated for soldering, that heat is being conducted along the piping and heating the air, expanding it. It either increases pressure if it is trapped, or it just flows through the joint. Blowing through the joint at the 'wrong' time will compromise the joint.

    Seems to me that steam is a gas, and that it, too, expands as it gets heated. The water also expands considerably when it does a phase change from liquid to gas. I totally agree that water, in whatever form, is the biggest reason for a failed joint. But, let us look at two different situations: liquid water at the joint, and liquid water near the joint, taking liquid at the joint first.

    When there's liquid water at a joint you are trying to solder, until all of that water is converted to steam, you cannot get the temperature of the joint hot enough to melt the solder...while boiling, it stays at the boiling point of water which will vary based on the pressure, but let's take 212 as the norm. Solder melts a lot higher than that. In the process of boiling off the water, it creates steam Under adibiatic conditions (constant pressure), water expands by a factor of 1600x it's volume as it changes from liquid to vapor (steam). Guess what, that increased volume in a closed vessel will force its way through the weakest point...the joint you are trying to solder. This can contaminate the joint, wash away the flux, and is likely to create a bad joint, if you ever do get it hot enough to melt the solder.

    Then, lets take the situation where there's no water at the joint, but some near the joint...in our similarly closed vessel. You get the joint hot enough to melt the solder, but in the process now have not only the heated air, but the supersaturated air/steam mixture and guess what, it blows through the joint since it isn't open to the atmosphere. So, what caused this? Failing to provide a path for the expansion of the gas, and yes, steam is a gas, which goes back to my (maybe too simplified) statement, that to ensure you have the best chance of a good connection, make sure you have an opening to relieve the buildup of pressure. Mixing water vapor into the equation just makes the whole situation worse, but expansion occurs regardless, and under the right circumstances, can cause a joint to be bad. It comes down to the partial pressure gas laws...you can only mix so much of various gasses together before the pressure rises or the volume increases, and heating it will try to expand it.

    Leave the piping open to the atmosphere, and you have a better chance of getting a solid joint, water in the picture or not.
     
  20. Hackney plumbing

    Hackney plumbing Homeowner

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    If you go back and review the thread everything I have been telling you has proven to be true. Go back and read the post where I say the pipe has to be dried out. Water in any of its states is a bad thing......with a pipe open to atmospheric pressure or not. A pipe can be open to atmospheric pressure and still have water in any of its forms still in the pipe.

    Water will run to heat. Heat will draw water to your joint as you heat it. The water will then flash to steam. It basically steam cleans the flux off and then the joint. The joint will oxidize and the solder will not stick. The flux acts also as a wetting agent that allows the solder to flow. Some solders flow better than others and also have a wider pasty range.

    Bottom line. A pipe does not have to be open to the atmosphere if you have removed the moisture from the pipe In my earlier posts I expalined that plain and simple.

    . Opening a pipe to the atmosphere doesn't guarantee steam will not affect your joint. Steam will take all paths.....not just your open pipe to atmosphere,it will also blow your joint out.

    Air pressure has nothing to do with it. Its not the expanding air that could give you problems its the conversion of water to steam.

    I suggest everyone read up on proper soldering techniques from copper.org. You can have your own opinions but you cannot have your own facts.

    How I have installed piping and how I was instructed to install piping has worked just like my tests have proved.
     
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