Is It Just Me - or are new unions hard to get leak-tight?


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Old 05-22-11, 04:44 PM
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Is It Just Me - or are new unions hard to get leak-tight?

It seems like I really have to torque them, sometimes with large wrenches - particularly for larger ones, e.g. 1.25" or 1.5" unions in my hot-water heating system. Eventually, I do get them tightened. I wonder if a smooth, thin film of pipe dope on the mating surfaces would help? Maybe that would lubricate the sufaces and allow tightening with less torque.

With smaller unions, like 0.5" - 1", I don't seem to have this problem.
 
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Old 05-22-11, 05:08 PM
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I wonder if a smooth, thin film of pipe dope on the mating surfaces would help? Maybe that would lubricate the sufaces and allow tightening with less torque.
Of course... Its been done for yrs. Pipe dope is really a lubricant. You would put it on the threads which alows you to turn the union more for a tighter seal.

I actually think the newer unions have less bevel on the nose, compared to older unions.

Mike NJ
 
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Old 05-22-11, 05:35 PM
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Originally Posted by lawrosa View Post
You would put it on the threads which alows you to turn the union more for a tighter seal.
Mike NJ
OK, thanks. Would you smear a little dope on the mating surfaces, too?
 
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Old 05-22-11, 05:48 PM
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Would you smear a little dope on the mating surfaces
I do. It would help the nose slide in. I always use teflon paste. The younger guys swear by that rectorseal type stuff. I think it all has teflon, but its all a copy of the original that I used which is grip light or realtuff.

Thread Sealants

Mike NJ
 
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Old 05-22-11, 06:49 PM
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OK, thanks. I have been using Ace Hardware's dope, which has teflon. After time, it tends to get a little gummy, but works fine. And when I get it on my pants, the wife can't get it off in the laundry - so it must be good stuff!
 
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Old 05-22-11, 07:01 PM
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I have always put never-sieze on the threads, that way all of the energy you put in the wrenches goes to torque instead of fighting threads. if you are trying to seal liquids or gases teflon on the faces will work fine. Do not use it with steam the steam will etch right through it and begin cutting away at the union and you will start over. If for steam use a thread lubricant only.
xbank
 
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Old 05-23-11, 06:17 PM
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Thanks for all your help. My latest union is a new 1.5" Ward (USA). I've got it torqued about us much as I can physically do - and it's still weeping, slightly (with 12 psi boiler pressure). I have another Ward union, and may try it, along with your various suggestions.

Maybe I should try a Chinese union?
 
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Old 05-23-11, 06:59 PM
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How big of wrenches are you using? For 1-1/2 inch you need two 24 inch wrenches and you DO need to pull pretty hard on them.

Just because Ward is a US company does NOT mean that all their fittings are made in US foundries OR that any particular one is not damaged. You need to carefully inspect the mating surfaces for any damage BEFORE using a union. I have never used any kind of sealant or "dope" on ground-joint unions or the coupling threads although I will use a drop of machine oil on the coupling threads.
 
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Old 05-23-11, 07:16 PM
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Thanks, Furd. I had been using one 24" and one 18" - to reduce the chance of breaking a foot if one wrench slipped off. I just now tried two 24s, and got a few degrees more turn. But, I'm an old, 185-lb weakling. We'll see how it works.
 
 

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