Vapor leak at union

[capt-n haddock]

Hi all,

I've made some upgrades to my pot still, so now it moves from a 2" riser from the keg, into a 2" 90* elbow and then stepping down into a 1' lateral, with a union, then into another 1" 90* elbow which then reduces down to 1/2" (with another union) for the liebig condenser (see photo).

where I seem to be leaking is @ the 1" union (the vapor does not seem to be coming from any of the sodded joints). So, what should I be trying to do to reduce the leak? or should I simply be using flour paste to stop up the leak?

union photo

[acfixer69]

Since it's a mechanical joint connection break it open and look at the faces. It is not unusual for solder to run there if you are not doing soldering as a payday. Also unions halves are not interchangeable from different manufacturers.

[StillerBoy]

As acfixer stated about solder that may have run onto the mating surface.. and you may need to lightly work over the mating surfaces with some fine sandpaper to remove some debris left during the manufacturing process.. also clean the threads with some scotch brite pad, because sometime the threads are poorly made and leave a rough surface which makes it hard to tighten good enough..

Mars

[capt-n haddock]

alright, I'll give those points a try. thanks!

[still_stirrin]

Use PTFE (plumber's) tape on the union threads. It'll allow you to draw in the union tighter.

Also, I usually allow a little to wrap in the cup socket too when I wrap the threads. When the halves come together, the tape will help it close tighter (easier) without galling (copper has a tendency to gall with itself).
ss

[NZChris]

Vapor leaks are often caused by a blockage, and blockages are dangerous, so check for that first.

[capt-n haddock]

no, no blockages. but thanks for your concern. I can and have visually verified all of my piping. I guess I should mention that I noticed this during my vinegar & trash wash runs.

[capt-n haddock]

regarding the face of the union, if that's the issue, is there a good way to make the two surfaces mate better (or is this simply a matter of sanding down any rough edges)?

[acfixer69]

regarding the face of the union, if that's the issue, is there a good way to make the two surfaces mate better (or is this simply a matter of sanding down any rough edges)?

If it's a flaw in the union faces you may be able to use some lapin compound or jewelers rouge to seat it but if it is not a mating pair I would toss it and go with a new one. I would use ferrules to relapse it but that's me.

[OtisT]

You need to make sure that the copper nipple and cup (for lack of better terms) are aligned perfectly before threading the brass nut to the copper threads. I find tightening threads does not bring a misaligned Union into alignment. Otis

[Swedish Pride]

Use PTFE (plumber's) tape on the union threads. It'll allow you to draw in the union tighter.....

+1

bet it'll sort the problem at hand

[BlackStrap]

I use copper unions in my steam stripper setup, connecting the 2 boilers together. When I was fitting everything up and soldering things together the connections between the 2 boilers is interchangeable physically.

However when flipped end for end the one union connection has a slow drip (It's water vapor, so no worries BUT it bugs the %^& out of me)...

In other words the union halves are not interchangeable or a slight mismatch causing my drip...

My Solution.
Mark the direction of vapor, ( Sharpy marker works)
Take apart the unions,
Check the mating surfaces, There will be some discoloration where the mate together.
Polish if need be, and always assemble in the same direction.

+1 Like others have said PTFE tape works well and keeps things dry and from gulling up.

[bronctoad]

On my old rig I had the same set up as your picture, mine also leaked at that joint.
what I found to worked well is 3 or 4 wraps of ptfe tape on the ball of the union.
when applying the tape keep it stretched tight so the tape on the pipe side of the ball
wont interfere with the nut coming up against the ball. you might have to work the nut
opposite of the tape wraps a couple of turns to get it over the ptfe with out balling it up.
that trick will worked but you have to make sure your union is in position before you tighten
it up. you cant rotate the union faces after its been snugged, so assemble your whole rig
then tighten all the fittings. you also have to replace it every time, tedious but it works.

Bronctoad

[Chauncey]

Use PTFE (plumber's) tape on the union threads. It'll allow you to draw in the union tighter.

Also, I usually allow a little to wrap in the cup socket too when I wrap the threads. When the halves come together, the tape will help it close tighter (easier) without galling (copper has a tendency to gall with itself).
ss

This

I find Union leaks are fixed by PTFE taping the socket side only. Even though a wrap on the threads def isn't gonna hurt. I had read it somewhere in the forum tried it once now I tapem every time and haven't had a leak since

[capt-n haddock]

Allmyexsliveinhell : Geaux Saints!

Then, thanks for all the responses everyone. In pulling apart the union, it seems like the ball & socket simply won't be a tight fit (they were bought as a unit, but I never paid any attention to the quality of the fitting until now), baring me doing a lot of filing on the socket to make it work. which seems like a fools errand really. So what I see is that I have two choices: find a new quality union with good fitment, or find a 1" tri-clamp ferrule.

My plan has been to upgrade to tri-clamps all along, but when I look for 1" clamps, i'm not seeing anything other than SS ferrules (seems like 1.5" is the smallest copper ferrule that I can find. And while I like SS, I have no idea how hard it would be to solder to copper. Any guidance there?

[cob]

regarding the face of the union, if that's the issue, is there a good way to make the two surfaces mate better (or is this simply a matter of sanding down any rough edges)?

If it's a flaw in the union faces you may be able to use some lapin compound or jewelers rouge to seat it but if it is not a mating pair I would toss it and go with a new one. I would use ferrules to relapse it but that's me.

this is the least expensive and most practical advice given. it will work.

you can use almost any toothpaste as lapping compound.

just put the joint together loosely with compound and rotate until you have a polish line around both pieces.

[Kareltje]

Sometimes I find some of the unions sweat a bit. Drop by drop and when I collect these drops, they do not contain any alcohol. So I don not care much about it, just put some white tape around them if need be.
But of course your leaks might be different.

[capt-n haddock]

Sometimes I find some of the unions sweat a bit. Drop by drop and when I collect these drops, they do not contain any alcohol. So I don not care much about it, just put some white tape around them if need be.
But of course your leaks might be different.

in this case, because I was doing the vinegar run, I was able to taste the condensate leaking out of the union, and it was vinegar, same with the vapor coming from the union. what's interesting is that I pulled the still apart today, and was looking at the union, and you could see the staining of the vinegar on the ball & socket where the joint is not mating fully.

it seems like the shoulder of the socket is not deep enough / wide enough to mate fully with the ball.

[still_stirrin]

You can use some fine sandpaper/emory cloth to reduce the “shoulder” a little. But, PTFE will help you in the end. (experience with this).
ss

[Chauncey]

regarding the face of the union, if that's the issue, is there a good way to make the two surfaces mate better (or is this simply a matter of sanding down any rough edges)?

If it's a flaw in the union faces you may be able to use some lapin compound or jewelers rouge to seat it but if it is not a mating pair I would toss it and go with a new one. I would use ferrules to relapse it but that's me.

this is the least expensive and most practical advice given. it will work.

you can use almost any toothpaste as lapping compound.

just put the joint together loosely with compound and rotate until you have a polish line around both pieces.

is there a brand of toothpaste that is prefered for this? just curious for my future reference. i figure toms of maine or perodontax or colgate or crest might be of very different grittinessess(sic) and work differently.


also to the OP regarding finding smaller tri clamp ferrules you could just flare/flange it out yourself. ive seen smaller diameter tubing flared for TCs before.

[cob]

regarding the face of the union, if that's the issue, is there a good way to make the two surfaces mate better (or is this simply a matter of sanding down any rough edges)?

If it's a flaw in the union faces you may be able to use some lapin compound or jewelers rouge to seat it but if it is not a mating pair I would toss it and go with a new one. I would use ferrules to relapse it but that's me.

this is the least expensive and most practical advice given. it will work.

you can use almost any toothpaste as lapping compound.

just put the joint together loosely with compound and rotate until you have a polish line around both pieces.

is there a brand of toothpaste that is prefered for this? just curious for my future reference. i figure toms of maine or perodontax or colgate or crest might be of very different grittinessess(sic) and work differently.


also to the OP regarding finding smaller tri clamp ferrules you could just flare/flange it out yourself. ive seen smaller diameter tubing flared for TCs before.

brand doesn't matter most toothpastes have either silica or calcium carbonate as abrasive ingredients,

and cleanup is easier than a grease based lapping compound. the grit is close to the same for most toothpaste.

[Chauncey]

Cool. Good to know.