Leaking unions. How to fix?

warno

I know it has been beat to death on the past but I'm wondering if there are any new ideas on sealing unions? More specifically copper unions. I have 4) 1" copper unions on my plate heat exchanger and testing 2 of the 4 they both leaked. I tightened them, with a 10" pipe wrench, to the point I was uncomfortable with anymore torque. Still leaked. I tried alittle grease on the mating surfaces and the nut threads. Still leaked.

Any sure fire way to get a seal on theses things? I'm hoping the answer is not replace them. Any help would be greatn thank you.

MikeL_2

I'd try wrapping the union mating face with quality teflon tape, and be careful where you contact the nut when tightening; copper union nuts are rather thin walled and easy to warp out of round under tension from a wrench. We always grasp the nut near its rear .........

warno

With air testing it's hard to tell if it's a "drip" leak because it makes soap bubbles like crazy.

hot_rod

POS, most copper unions, not worth the $$.

The best way to assure 100% seal is solder the two halves together

warno

I have read you tell that to a member in an old thread. Before I go that route are you serious? Can you still tighten the nut when you're done?

hot_rod

Your call, some of the low quality unions just will not seal. Thermal expansion from heating and cooling can cause leaks to disappear and reappear as the system runs.

If you flux both faces and the threads around the union nut, no you cannot turn the nut, you have an expensive sweat "coupling"

If you slide the nut back, just solder the faces, the nut can be spun back on. But that would be a dirty trick to play on the next person that tries to remove the connection

Gasketed, o-ring, or flange pairs with gasket are a better way to build a union.

If it is not a union needed on a regular basis, to service a component, why bother?

warno

I got theses in a box of surplus inventory. And I can't tell what manufacturer they are, guessing cheap. I wanted unions on my heat exchanger in case it got clogged and needed cleaned out. Even though I have strainers before each side. I was concerned about using the unions for this reason. I guess I know now.

Larry Weingarten

Hello: I've had good luck putting a turn or two of Teflon tape on the union threads and then just catching the threads and letting tape overlap the actual joint. This has let me tighten the unions up better because of the lubricating action of the tape. I agree with Bob that "O" ring unions actually work!

rick in Alaska

I have also found that if you tighten it up good, then back it off and tighten it again, that it will go a little farther on the second go around. This also works on electrical terminals.
But I am with Hot Rod... if I can avoid them , I will.
Rick
Rick

Bio

warno said:

I got theses in a box of surplus inventory. And I can't tell what manufacturer they are, guessing cheap. I wanted unions on my heat exchanger in case it got clogged and needed cleaned out. Even though I have strainers before each side. I was concerned about using the unions for this reason. I guess I know now.

A compression coupling will do the job, in case of an emergency a removable sharkbite can work as well

warno

I'm so leary of the shark bite fittings. They just seem like a leak waiting to happen.

I think I'm just going to sweat it together and fix it next year. I'm running out of time.

Danny Scully

The best thing to have done was install isolation/purge valves. You could have cleaned the heat exchanger that way.

warno

I have webstone propals at each end of each side of my heat exchanger, I've just heard of people getting them gunked up with stuff that almost needs a soak to remove.

On a side note I decided to give it one last try with the wrenches before going the solder route. I put a VERY uncomfortable amount of torque on the union fitting and it seemed to finally quit bubbling the soapy water. I will definitely take note of this and never use copper unions again or at least not without a gasket sealing surface.

Thanks for all the help everyone.

EBEBRATT-Ed

Use the NIBCO #733 union with the brass fitting. They are pretty good and usually don't leak.

Stay away from the NIBCO #633 wrought copper union 50% of them will leak in my opinion.

problem is most supply houses stock the #633 and they are horrible you always have to dope them.

Harvey Ramer

An uncomfortable amount of torque has always worked for me. Lubricating the threads and the back of the Union nut allows you to turn it a bit tighter.

Ironman

A judicious amount of Teflon paste on the mating surfaces and strong forearms usually works.

The problem is that the mating surfaces of these Asian fittings are not ground together, so the paste and some extra umff tend to compensate.

Oiling the threads, like Harvey suggested, will also help.

ChrisJ

Personally I'd never trust any sealer on the mating surfaces of a union. That's not the intent of thread sealer nor the way a union is designed to seal. If that goop ever gets pushed out, it will start leaking again.

Clean, dry mating surfaces and a dab of pipe dope on the threads of the union to lubricate it.

I don't know what size unions these are, or what material they are but on a black iron 1/2" union I'd throw a 12" and 14" wrench on it. They will take a whole lot more torque than a copper and brass union. You might even try a 14" and 18" wrench on a 1/2" steel union, but don't get carried away.

warno

These are 1" junk copper unions I'm using. I used a 12" wrench and a 10" pipe wrench on the nut. I know the pipe wrench isn't right for the nut but I didn't have a wrench big enough for it other then that. Anyway. I layed the pipe wrench against my forearm and started turning. Things felt bad as it was going. But it stopped leaking.

If I ever have to break them apart again they are getting replaced with gasketed flanges.

warno

This morning I finally got around to finishing up the rest of the system and could check my other 2 unions. And wouldn't ya know it, they leaked too. So that's 4 for 4 on the china express unions leaking. I am definitely taking note of this for future reference.

I ended up breaking the leakers back down and putting dope on the nut threads and the backside of the mating surface I hopes it would lubricate the turning items to get alittle more out of them. It seems to have worked. At 70 psi I have one little tiny bubble that shows up every one in awhile but I'm hoping that stops with heat and alittle scale build up.

pecmsg

Never Seize

warno

I have heard that before but I have heard that that stuff can affect rubber seals. I know I'm not going to glob it on like the idiots at work do but I worry about it getting intrained in the water and going places I don't want it.

john p_2

I agree with Ironman and disagree with most....have never had an issue with die electric or copper unions. Teflon paste on the mating faces of the copper unions and not over tightening them.

As for die electrics I only use Never Seize on the gaskets and only a thin film on each side.