ripsnortMN
Well-known member
Does a black pipe union usually leak at the threads? Installed a brand new one and I’m getting bubbles near the thread where the two halves screw to each other.
Black pipe union leaking
- Thread starter ripsnortMN
- Start date
Usually, no.
Make sure both halves are from same mfr.
Take it apart and pipe dope the inner threads and the machined faces lightly.
Make sure the pipes entering the union are not skewed where the union is forced to align both opposing pipe sections.
Make sure both halves are from same mfr.
Take it apart and pipe dope the inner threads and the machined faces lightly.
Make sure the pipes entering the union are not skewed where the union is forced to align both opposing pipe sections.
what mm said.
actually, the threads of the union are not sealing , the machined faces are the sealing areas ( of course the pipe threads are sealing too)
also check the mating surfaces for any imperfections that would cause them not to seal
actually, the threads of the union are not sealing , the machined faces are the sealing areas ( of course the pipe threads are sealing too)
also check the mating surfaces for any imperfections that would cause them not to seal
housewolf
Well-known member
This.
You didn’t mention what size it is but you need to roll your sleeves up, get two pipe wrenches (one for a back up), and tighten it up pretty good. You’re not going to hurt it.
nadogail
Well-known member
pipe Unions, in my limited experience, don't like to be misaligned. I am careful to check the country of origin on critical fittings.
OP
ripsnortMN
Well-known member
These are china 1/2” union. The Black pipe is nice and even on the approach when screwing together. I tightened it extremely tight and still leaked. I resorted to putting pipe dope on the mating surfaces and also the threads. It’s holding a seal now. Imho it’s completely ridiculous that I would need to put sealant on the mating surface of the union for it to seal. But I guess after all it is made in china. On a side note, this is the second union I’ve had to install. The first one I tried was actually leaking through the casting.
housewolf
Well-known member
I agree, it shouldn’t be needed but I put a thin coat on the surfaces and maybe a drop on the big threads for lube. I almost never have one leak, and I’m not one to use pipe dope for “good luck”
BillK
Well-known member
Is this an air line ?
OP
ripsnortMN
Well-known member
No. Converting my propane furnace to natural gas.
D45
Well-known member
True Value sells Anvil brand, USA
Couldn't pay me enough to use a Chinese union for gas.
OP
ripsnortMN
Well-known member
It’s funny you say that. All of the Chinese black pipe that I’ve used has leaked and will only seal when using yellow gas tape and pipe sealer combined. Also torqued to 80flbs.
ratflinger
Well-known member
well, answered your own question.
HoosierBuddy
Well-known member
I buy a lot of gas fittings for work. I don't get them at a box store, I get them from a wholesale plumbing supplier.
I'm not saying these are all US made either, but I'm not seeing any difficulties in getting them to seal at pressures many times what you are going to have in your home. When manufacturing switched to China (mostly Taiwan) 15 or 20 years ago, there was a huge uptick in issues, but that kind of went away within a few years. Maybe the box stores are getting them from even cheaper sources now.
Anyway..I think you can walk in and buy fittings retail from a wholesale plumbing supply company....correct me if I'm wrong. They sell 99.9% to plumbers, and they aren't going to be able to get away with selling junk.
Of course the union doesn't need pipe dope to seal on the face, or at least shouldn't....but using the correct pipe sealant helps a lot. I've used many different kinds over the decades, and I haven't found anything better than rectorseal #5. There may be something better, but I haven't found it....and it's non-setting so you can get your joint back apart 10 years from now if you need to. Stir well. Brush it on. Let it tack. Assemble. I don't use teflon tape on gas fittings anymore. It does work most of the time, but it's harder to get leak tight than a good pipe dope.
I'm not saying these are all US made either, but I'm not seeing any difficulties in getting them to seal at pressures many times what you are going to have in your home. When manufacturing switched to China (mostly Taiwan) 15 or 20 years ago, there was a huge uptick in issues, but that kind of went away within a few years. Maybe the box stores are getting them from even cheaper sources now.
Anyway..I think you can walk in and buy fittings retail from a wholesale plumbing supply company....correct me if I'm wrong. They sell 99.9% to plumbers, and they aren't going to be able to get away with selling junk.
Of course the union doesn't need pipe dope to seal on the face, or at least shouldn't....but using the correct pipe sealant helps a lot. I've used many different kinds over the decades, and I haven't found anything better than rectorseal #5. There may be something better, but I haven't found it....and it's non-setting so you can get your joint back apart 10 years from now if you need to. Stir well. Brush it on. Let it tack. Assemble. I don't use teflon tape on gas fittings anymore. It does work most of the time, but it's harder to get leak tight than a good pipe dope.
fitter30
Well-known member
Always use a back up wench when tightening or loosening fittings. Take the back up wench hold it tight to the union nut with other wench hammer the nut once tight nut again it will gain a 1/8 turn.
Especially if it's leaking with almost no pressure that natural gas has.
rlitman
Well-known member
Rectorseal #5 is all I would use with gas threads. In a brush on form, I too don't think there's anything better. I've had it get runny and leak when applied to a threaded fitting that is sweated after assembly, but that's not applicable to gas.
As for a better option, the best I can suggest is La-Co Slic-Tite Stik with PTFE. And when it comes to applying a sealant to the sealing faces of a union (which technically SHOULD seal metal-to-metal), this weird big crayon is much better than any paste dope. Just draw on the two sides with the crayon until they're white, and it's like a headgasket in a crayon.
Oh, and I won't take credit for this idea. I picked it from a service man from my gas company who was taught to use this as company policy on the union fittings on gas meters in my area. If it's good enough for those two unions, it's got to be good enough for the rest of the ones downstream.
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housewolf
Well-known member
Pipe Dope -
Rectorseal #5 is my go to as well. I started running screw pipe back when if there was anything available beside Rutland Red, I didn’t know about it. Old timers talked about linseed oil mixed with Portland cement. I don’t know it all but I’ve put more than a reasonable amount of thought into this and I have a pretty good bit of experience. I’ve run jobs with over a hundred pipe fitters and plumbers installing pipe for two years. Guys would come up to me and request “Leak Lock” pipe dope. It’s good stuff and I guess if you are making tens of thousands of joints and you’d have 13 leaks using rectorseal and only 9 using Leak Lock, it would make sense to use the blue stuff. My way of thinking evolved to; I know the yellow stuff is good and if the only thing making .0004% of my joints leak is the color of the pipe dope (yes I realize it’s an entirely different chemical) am I maybe not just putting a patch on a bad fitting, bad threads, pipe not tight enough etc… and compromising the integrity of the system?
The most consistently difficult threads I’ve had to seal are copper male/female adapters that have been brazed (medical gas). Brazing anneals the copper and the threads often begin leaking after they’ve been tested. X-Pando is what you seek there.
Just my $0.02… probably about what it’s worth
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mike93lx
ALLIANCE MEMBER
Whether you got it to stop leaking or not, I bet you'll never feel comfortable with it. I'd replace it with something higher quality
HoosierBuddy
Well-known member
Yeah...I went thought a Leak Lock phase myself. It lasted about 2 years.
At a gas company you end up having to reconfigure piping some of the time. Leak Lock sets hard and it is extremely difficult and sometimes impossible to disassemble a completed joint after it has set up completely. We've had items like cast aluminum gas meters with NPT female threads where we completely destroyed the aluminum castings trying to get pipe ******* out of the meter.
When you're dealing with trying to disassemble a 4-inch NPT ****** from a gas meter, you've got a tough job in front of you regardless. If Leak Lock was used? You can just about guarantee you'll be scrapping the meter before the day is out. Leak Lock might be the berries for someone....but not me. Lesson learned.
Firebrick43
Well-known member
Last place I worked had a guy go nuts with the leak lock. I was a team lead/supervisor and I absolutely refused to work on it.
It was either all cut off and replaced or someone else could do it, and I normally volunteered the guy that applied it.
They balked at the cost at first when I started replacing whole sections instead of the individual piece that was leaking but i am not a bad pipe fitter and could measure, order fittings, and make up the assembly. Then I could replace the whole assembly in 30 mins instead of hours of down time.
I also demoed the quality difference of anvil and ward fittings. The maintenance manager convinced the plant manage to require the bean counters to attend. Had no issues ordering American fittings from supply house.com
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I wish I had a backup wench
a lot of thread leaks in pipe are caused by overtightening & stretching the threads .
I realize this thread started with a joint @ a union. we always lightly doped them on the sealing surfaces too .
I realize this thread started with a joint @ a union. we always lightly doped them on the sealing surfaces too .
claymont
Well-known member
Over the years I've hammered a lot of unions into submission
Mr onetwo
Well-known member
These are just opinions
....Rectorseal #5 *****.I stopped using that **** years ago and went with this stuff. https://www.supplyhouse.com/Blue-Mo...avy-Duty-Industrial-Grade-Thread-Sealant-8-oz As to unions...start with a light touch tightening them to leave yourself room and always dope the mating surfaces.I suspect that chinesium unions warp as they are tightened, but I always use JP Ward unions. Back in the day we used to use "Dart" unions which were heavier with brass to brass seats.
....Rectorseal #5 *****.I stopped using that **** years ago and went with this stuff. https://www.supplyhouse.com/Blue-Mo...avy-Duty-Industrial-Grade-Thread-Sealant-8-oz As to unions...start with a light touch tightening them to leave yourself room and always dope the mating surfaces.I suspect that chinesium unions warp as they are tightened, but I always use JP Ward unions. Back in the day we used to use "Dart" unions which were heavier with brass to brass seats.
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disston
Well-known member
Pipe threads like sealing tape or dope. I use one or the other, some use both, but not me. They also like really, really tight.