Leaky Union Fitting

Jim Leong

One inch union on steam radiator has slow drip at the mating surface. No play in pipes to take fitting apart since ends are in concrete. I may be able to loosen union nut. Any suggestions to stop the drip. THANKS.

Bob Gagnon plumbing and heating

just try

tightening the fitting. bob

ed wallace

leaks

back off union nut apply pipe dope retighten union nut

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Jackchips

You might

also be able to wrap a little wickin around the union with the pipe dope before retightening.
Good luck.

Larry_7

Long Shot

If simply tightening the union nut won't work, sometimes re-positioning the mating surfaces will be enough to stop the leak. You have to break the nut loose, then tighten one half of the union a bit, then crank nut back tight again. Sometimes it's just enough to stop the leak.

Hope this helps,

Larry

Frank_5

unions.....

In my experience, trying to overtighten a small union will result in "egging" the collar, then it just won't make up. Try this: Loosen the collar and put a few turns of wick and dope on the machined end of the union, the one that has the collar attached, not the one that the collar attaches to. Try to get some dope onto the mating surfaces also. Then, as you tighten the collar, keep hitting it with a hammer, a few strokes at a time on all the surfaces you can reach, using a glancing blow in the direction you want the collar to turn. I'm not saying to use a lump hammer, but something like a 22 oz. claw. If it is out-or-round, being maleable and hitting it might allow it to become a bit truer, and let it make up enough to stop leaking. Worth a try.

Larry_7

Oops misread post

Didn't notice it was a rad union.

Larry

kevin_5

RTV silicone

OK, it's unorthodox, and it may get me "excommunicated" for even mentioning it, but I'll bet that if you drain the water, smear a little automotive RTV silicone in the union surfaces and let it set up for 30 minutes it will stop the leak. It holds that kind of heat and pressure every day in automotive applications, and since we're already trying to introduce a foreign substance into the mating surfaces of the union, (wicking and dope)why not something that will do the job whether it's traditional or not? If it is applied right, I guarantee it will stop the leak. Have I tried it? Not in this application, but many, many times in oil and water sealing problems in auto mechanics. Many times that's ALL they use for gaskets in OEM applications, and it's comparatively easy to disassemble and remove if you have to. Use your favorite color, wipe it off so noone has to see it when assembled, and it will do the job without relying on extra torque to overcome a bad seal. "Plastic" tubing in a floor was no doubt considered heresy at one time, so please don't hold an Inquisition for me guys. :-) Kevin

Nobby

I was going to suggest the same thing.
As a Marine Engineer this is a repair I have applied many times to unions carrying many various pressures/temps/fluid types. In my armoury are several types of method.
1. If you can create a small gap in the mating surfaces take a feeler gauge or shim stock and smear appropiate rated sealer such as Permatex Ultra Copper. The key is upon reassembly to not overtighten. Initially just pinch up the fitting and then allow sealer to set and form a gasket. Then after several hours tighten some more. Do not lean on it you will squeeze out the gasket. I usually slightly undertighten and then snug up if required. An old marine engineer taught me the merit of modest tightening in that you always have somewhere to go and you don't deform strip anything. Overtighten and you have nowhere to go, kinda like getting stuck in 4 wheel drive mode!
2. Use an o-ring of correct size Buna is good to 250F Viton is good to 400F. As in number 1 do not overtighten you risk squeezing it out.
3. Use Teflon valve stem packing good to 550F you can get it as small as 1/16". Make a ring and make sure you cross the ends, apply like an O-Ring. Overtightening is less of an issue with this one.
I have ordered this somewhat in ease of material availbility. These methods are somewhat dependant on creating a small gap. If no gap can be created then I agree with Franks method though I usually up the ante and use gasket sealer or teflon style dope such as Loctite 565 or 592(which you won't find at Home Depot)!

I hope this does'nt get me thrown off the Wall on my second Post.

Nobby

I was going to suggest the same thing

I was going to suggest the same thing.
As a Marine Engineer this is a repair I have applied many times to unions carrying many various pressures/temps/fluid types. In my armoury are several types of method.

1. If you can create a small gap in the mating surfaces take a feeler gauge or shim stock and smear appropiate rated sealer such as Permatex Ultra Copper. The key is upon reassembly to not overtighten. Initially just pinch up the fitting and then allow sealer to set and form a gasket. Then after several hours tighten some more. Do not lean on it you will squeeze out the gasket. I usually slightly undertighten and then snug up if required. An old marine engineer taught me the merit of modest tightening in that you always have somewhere to go and you don't deform strip anything. Overtighten and you have nowhere to go, kinda like getting stuck in 4 wheel drive mode!

2. Use an o-ring of correct size Buna is good to 250F Viton is good to 400F. As in number 1 do not overtighten you risk squeezing it out.

3. Use Teflon valve stem packing good to 550F you can get it as small as 1/16". Make a ring and make sure you cross the ends, apply like an O-Ring. Overtightening is less of an issue with this one.

I have ordered this somewhat in ease of material availbility. These methods are somewhat dependant on creating a small gap. If no gap can be created then I agree with Franks method though I usually up the ante and use gasket sealer or teflon style dope such as Loctite 565 or 592(which you won't find at Home Depot)!

I hope this does'nt get me thrown off the Wall on my first reply to a Post.