Could this have been avoided?

[MrEd]

Hi all.

I had my first fire(a small one) with mixed results yesterday. Had pressure tested my system upto 30psi and it held. (Could not test any higher because of the pressure relief valve). Feeling confident, I filled the system with water, and it held - no leaks. Ran the circ for a while with just cold water, also no leaks.

Started up the fire and it ran about 2 hours and I had a blowout (one of the soldered joints developed a leak) in one of my copper lines - quite a mess, (in the cellar at least). Have spent the last 24 hours (except for sleep), draining the lines, and re-pressure testing this time upto 45 psi this time (i took out the releif valve).

Question is, as of right now I am holding steady at 45PSI(with air), the system should never exceed 30PSI when its running, and in fact yesterday when I was doing a test burn never got above about 18psi, so why did my joint fail? Now I am nervous about firing it up again.

My past experience with plumbing (not heating systems though) has always been, if it doesn't leak right away, it never does...but in this case, as the circulating water got up to about 160 it failed.

Did the high temperatures cause this failure of a marginal joint? Before I re-fill and re-start the fire, any other advice?

 

[wtom24]

What type solder did you use? Most probable explanation is that the joint didn't "take" and the solder did not wet the entire joint. Carefully clean the joint, apply flux and try again. Should be good to go... Normal water temperatures of less than 200 degrees shouldn't appreciably weaken solder joints. Another cause could have been thermal expansion-is the system piped so expansion forces do not place undue stress on any of the joints?

 

[steam man]

Was the joint in close proximity to the boiler? I am just thinking that it was cold soldered. If the pipe was larger, 1" and over, there's a chance it was a cold joint. I believe typical soldered joints are good for about 280 deg F under pressure. If I can test just pipe and fittings I will go up to 90 psi. Don't fret it, fix it and fire again.

Mike

 

[BrownianHeatingTech]

As others have said, it sounds like the joint didn't actually take the solder. Having explained this to an apprentice recently, perhaps I can clear up the details of what happened...

Before soldering, the surfaces need to be cleaned of corrosion, oils, etc. Wire brush or sandpaper takes care of that. Some folks will say not to bother on anything that "looks clean," but for the extra couple seconds it takes to properly clean each joint, I always do it...

Then, flux is added. The flux serves to acid-etch the mating surfaces of the pipe and fitting, cleaning any remaining oil and such from it, and to draw the solder into the joint. The rule of thumb is that solder will only flow where the flux is. So you want to make sure there is adequate flux inside the joint, and if aesthetics are important to you, then you want to make sure to wipe excess flux away from the outside of the joint after you heat it, but before you add the solder.

What can happen, particularly on larger fittings or other hard-to-heat connections, is that you spend so much time heating the joint, that the flux melts and runs away, leaving nothing to draw the solder into at least some portion of the joint. Since there was flux on the surfaces to begin with, there is often solder attached to the outside edge of the joint, and you won't see that there is none behind it.

The thin bead of solder formed in a "cold" joint is often enough to hold back air pressure, when cold. After the first heat cycle, the expansion of the pipe and fitting shift them slightly, breaking that thin bead, and exposing a gap in the solder.

Joe

 

[webbie]

I concur.....

First of all, the boiler should be run at 15 PSI or less in most cases.....and copper pipes can easily take many times that - my household pipes (DHW) were up at 100 PSI at one time.

Neither heat nor common pressures (up to 60-75 PSI) will make a proper solder joint fail.

Preparation is the key, as Joe says. Proper cleaning, fluxing, slow and even heating and the drawing in of the solder will result in almost 100% success - although large pipes - over 1 1/4", are definitely tougher.

 

[MrEd]

I suspect you are right, I did clean and flux all joints. First time I have worked with the 1.25 copper, so I suspect my technique left something to be desired. Anyway, I am all filled up with water, and tarm is heating up now...we shall see....

 

[kevindauch]

Hi MrEd,
I experienced the same problem. I switched from Home Depot solder to a solder from a plumbing supply place (I believe that it was a 5 percent silver solder) and had better results. It was easier to work with and had of a lower melting point, hence the less chance of heating the flux out of the fitting.

 

[NHFarmer]

I had a couple of leaks,I had to take them apart and redo them.All part of the adventure.You should be good to go.Congrats on the firs burn!

 

[MrEd]

Well I am happy to report, I now am having a successful 2nd first burn. (I am calling this the first one, the one with the water shooting everyplace can't really count, can it?) All in all had to fix 3 tiny leaks that I suspect were because of weak joints that cracked on the first warmup when the pipes expanded.

It was a trick getting all the air out of the system, but now hot water is flowing in all 5 zones of the house - not sure if I actually have "gasification", but I got heat, and that is all that matters to me for today!

 

[Tony H]

I went thru the same thing and found that using silver solder instead of the basic stuff from the big crap stores and using Mapp gas to heat quicker make a big difference on the 1" and larger pipes.
Way to go! It's a great feeling when you got heat.

 

[MrEd]

Next time I'll try a different solder - didn't even occur to me that the quality may make a difference. I had 3 rolls sitting in the toolbox for about 15 years and just grabbed what I had. Oh well, live and learn. I do use MAPP gas, much hotter than the regular torch I used to have.

 

[BrownianHeatingTech]

95/5 (tin-antimony) solder is the way to go. Lead is a pain.

MAPP or acetylene are the only ways to go. And a decent torch. Something like a Lenox LT91, Turbotorch TX504, or similar size. Anything smaller isn't worth the MAPP.

For ultimate control, an air-acetylene kit using a B-tank is the way to go. Various tips can give you anything from a pencil flame for soldering 3/8" M copper right next to a beam, all the way up to a 1/2" tip that can solder 4" copper (or solder a smaller pipe which still has a bit of water in it!). Of course, a good kit will set you back close to half a grand by the time you get it all together, but it's definitely worth it if you're in the trades...

Joe

 

[chuck172]

I've been on jobs where thousands upon thousands of copper joints were tested. Then one day, pow, a joint lets go. Never even soldered, but it held pressure. Don't ask me how but it did.
I use 95/5, then back it up with a bead of 50/50. Main thing is to be clean, don't handle the joints once they are clean. Use a big enough tip. You need allot of heat but not so much as to boil out the flux.

 

[BrownianHeatingTech]

Main thing is to be clean, don't handle the joints once they are clean.

Indeed. And if you test-fit something, then take it apart to make an adjustment, make sure to add some more flux before putting it back together.

Use a big enough tip. You need allot of heat but not so much as to boil out the flux.

Always easier to hold a too-big torch a bit further away, compared to having a torch which cannot heat the joint properly. Err on the side of "big" and pay for a bit of wasted gas, if you have to err one way or the other...

[edited to add] As heaterman says below, don't overheat the joint. If you are using a larger torch than you need, be careful to hold it far enough back to keep from cooking the flux away.

Joe

 

[heaterman]

I think that I have seen as many joints fail from overheating as I have any of the other good reasons given above. If you burn the flux you're basically asking for a problem either immediately or down the road, especially if there's antifreeze involved.