Union joint leak

[rbsc]

I’ve been pretty proud of my soldering job, no vapor leak so far. But I cannot stop a little drop of liquid from dripping out this joint now and then, unless I crank it down unnaturally tight. Obviously, I have a strip of Teflon under there. I mean I’m cranking on this thing so hard I’m afraid I’m going to break something. Is that something that would make you shut the whole thing down? For now I have wrenched it so tight I think it has stopped, but that happened about 15 minutes ago and sprung another little drop.

[NZChris]

Pressure causes leaks, so look for restrictions. If the temperature is high for the boiling point of the wash, shut down and look for a blockage.

Does a drip every now and again really matter?

[Steve Broady]

It’s a lot easier to do before everything is soldered together, but what I did was to put a little abrasive paste between the two mating faces and rotate them against each other, lapping them together.

Try putting something like sharpie all over one face, rubbing it agains the other, and see if there’s a spot that isn’t making proper contact. You should see a continuous ring of bare metal rubbed through the sharpie, from relatively minor pressure on the pipe. If you don’t, try lapping the faces.

[rbsc]

Pressure causes leaks, so look for restrictions. If the temperature is high for the boiling point of the wash, shut down and look for a blockage.

Does a drip every now and again really matter?

No thermometer so no way to know that for sure. I drop now and then doesn’t matter to me as far as volume loss if that’s what you mean, just worried that I’m doing something stupid by continuing. In other words is it like a vapor leak for you shut down immediately.

[rbsc]

It’s a lot easier to do before everything is soldered together, but what I did was to put a little abrasive paste between the two mating faces and rotate them against each other, lapping them together.

Try putting something like sharpie all over one face, rubbing it agains the other, and see if there’s a spot that isn’t making proper contact. You should see a continuous ring of bare metal rubbed through the sharpie, from relatively minor pressure on the pipe. If you don’t, try lapping the faces.

Great thought, thank you

[NZChris]

Disconnect it and blow through it to check that you haven't built a bomb.

Use more tape when you put it back together.

[Salt Must Flow]

I'd replace it. Unions shouldn't leak. You shouldn't have to ever use PTFE tape on union connections either.

[elbono]

It’s a lot easier to do before everything is soldered together, but what I did was to put a little abrasive paste between the two mating faces and rotate them against each other, lapping them together.

Try putting something like sharpie all over one face, rubbing it agains the other, and see if there’s a spot that isn’t making proper contact. You should see a continuous ring of bare metal rubbed through the sharpie, from relatively minor pressure on the pipe. If you don’t, try lapping the faces.

Yes, pipe unions seal inside, spherical faces usually. Tape on the threads won't help. There are two faces where the seal happens, they needs to be clean and smooth.

If you want to use tape it needs to between the seal faces but I wouldn't expect that will work.

[rbsc]

Yeesh, this hobby hates me. Always something. Thank you for your help, everyone.

[elbono]

Yeesh, this hobby hates me. Always something. Thank you for your help, everyone.

I hate pipe unions!

Fought them for 40 years at work, never won, best was a draw. Now I use sanitary/triclamp fittings.

[Salt Must Flow]

Yeesh, this hobby hates me. Always something. Thank you for your help, everyone.

I hate pipe unions!

Fought them for 40 years at work, never won, best was a draw. Now I use sanitary/triclamp fittings.

I totally agree. Unions can be touchy, especially when you disconnect them often. Tri-Clamp fittings are wonderful. They're becoming more common and more affordable.

[Yummyrum]

I also agree , they shouldn’t leak . Tri-clamps are better .

But I wonder have you got it the right way round ? Ball at the top going into cup ?

I recall once having all manner of issues with some stainless unions . Discovered that there were new and old stock in the box at the shop .Someone had unscrewed some. I ended up with a miss matched pair . There apparently were slight differences in the mating surfaces

[NZChris]

I only have one of those and it is installed the other way up. If it leaked and it wasn't under pressure, I doubt I would know as any condensate would run back down to inside the joint rather than out past the nut. I only hand tighten it.

[rbsc]

I also agree , they shouldn’t leak . Tri-clamps are better .

But I wonder have you got it the right way round ? Ball at the top going into cup ?

I recall once having all manner of issues with some stainless unions . Discovered that there were new and old stock in the box at the shop .Someone had unscrewed some. I ended up with a miss matched pair . There apparently were slight differences in the mating surfaces

Man, I’m gonna feel dumb if I’ve messed up something this simple. Just finished so took it apart. This is how it goes, obviously the nut on the right tightens over the threads.

[acfixer69]

I also agree , they shouldn’t leak . Tri-clamps are better .

But I wonder have you got it the right way round ? Ball at the top going into cup ?

I recall once having all manner of issues with some stainless unions . Discovered that there were new and old stock in the box at the shop .Someone had unscrewed some. I ended up with a miss matched pair . There apparently were slight differences in the mating surfaces

Man, I’m gonna feel dumb if I’ve messed up something this simple. Just finished so took it apart. This is how it goes, obviously the nut on the right tightens over the threads.

That don't look like a matched pair union halfs.

[NZChris]

That looks upside down to me.

You could try using valve grind paste to get it to fit better.

Thread tape should be used on the round end, not on the thread.

Do you feel any resistance when you blow through it?

[Wildcats]

That picture looks like the one half is missing. Maybe it's just the picture. Or maybe one half is missing.... Hard to tell with that picture... If there is not two half's of the "ball" then it's never gonna seal.

[elbono]

Definitely not like unions I'm used to.

[rbsc]

Man, this is crazy. Leave it to me to get the wrong part. Someone on here recommended it but maybe they shipped the wrong one? The pic did upload sideways but it still sounds like I have the wrong one.

[Steve Broady]

That looks like the right thing. I think it’s just the angle of some of the photos, throwing things off.

I had the same problem with a few of the copper unions I was using, before I switched to tri clamps. The fix I suggested above, lapping the mating faces, solved the issue for me.

[Windy City]

It definitely looks like something is mismatched with that union.
The threads on the male part should be a larger diameter so to accept the other half into it.
Did you buy that from home depot or a chinese knockoff??

[rbsc]

It definitely looks like something is mismatched with that union.
The threads on the male part should be a larger diameter so to accept the other half into it.
Did you buy that from home depot or a chinese knockoff??

Mine is weird for sure. Just doesn’t make sense, ordered that exact one straight from Home Depot.

[Windy City]

That stinks that that is what they sent you.
I would replace it with a Nibco or Mueller brand.
That union is definitely not the one in the picture advertised.

[rbsc]

Screenshot from the video that goes along with the union. Still doesn’t look like the one someone posted above, but definitely has a better cup on the male end than mine.

[ruminant]

I've had a similar leak in the union connecting my lyne arm to my Liebig. Although it's about six feet away from my burner, I'm not comfortable with a vapor leak, so I wrap the union in a wet cloth several times and knot it. This condenses any leaking vapor into diluted liquid, and--now that I'm a little better at alignment--I end up with a drip every 15-20 minutes during a stripping run.

Any opinions on the safety of this work-around?

[elbono]

Your last pic looks like it was made that way to reduce the diameter but will be harder to get a seal.

Steve's suggestions should help but if you end up replacing it I would go with sanitary/triclamp.

Stainless/copper joints aren't as easy as copper though. I used 1" type M and needed to make a shim to compensate for the loose fit on the ferrule.

[jonnys_spirit]

I replaced unions on my liebig with small 1" TC fittings until I upgraded to a 2" shotgun. I keep the liebig for backup but the unions worked for a good while. Tightening/loosening with vice grips every run wore the mating surfaces out so I added TC fittings as a work around for a while...

I currently use unions on my smaller still but I never loosen them..

Cheers,
j

[rbsc]

Sounds like I have to replace it. It took me many tries to get decent at soldering so I’m really nervous about tearing it apart and doing damage to adjacent joints, but it sounds like that’s the only option. Thanks so much to everyone for their help.

[shadylane]

But I cannot stop a little drop of liquid from dripping out this joint now and then, unless I crank it down unnaturally tight. Obviously, I have a strip of Teflon under there.

Ya don't want or need any teflon tape on a union.
Use valve lapping compound to lap the mating surfaces for a perfect fit.

[Windy City]

Sounds like I have to replace it. It took me many tries to get decent at soldering so I’m really nervous about tearing it apart and doing damage to adjacent joints, but it sounds like that’s the only option. Thanks so much to everyone for their help.

If you are worried about melting other nearby joints you could wrap a wet rag around the joint you want left intact or try Cool-Jel.https://www.maxwarehouse.com/products/l ... fYQAvD_BwE
I have used this stuff for years and it is awesome. I was recently soldering a 2" line that was 2" away from a pvc drain stack and there was no charring, deformation or any signs of heat on the pvc when I was done. I wrap a dry paper towel on the areas I DO want heat and then spray the whole area. Remove the paper towel and you are good to go removing the old fitting. Do the same process when you are going to install the new fitting.