Home>Discussions>PLUMBING>1" threaded copper union leaking
8 posts / 0 new
Last post
1" threaded copper union leaking

I'm wondering what the proper way is to install a "ELKHART 33584 UNION C TO C 1" COPPER" (or similar) fitting to keep it from leaking

I had to replace the house water shut-off valve, and I had lots of trouble soldering due to the bending stresses of the existing pipes, so I cut the line downsteam and used a 1" copper threaded union to allow me to solder the joints in free air, then screw the last joint together.

The union uses a simple rounded seat and mating rounded head on the two pieces, and when I first assembled the joint and turned the water on, the joint leaked profusely through the threads. I took it apart used some teflon tape wrapped partly around the thread, and partly lapping into the seat of the joint.

After turning on the water, I got only a little slow drip, and with time it seems to be stopping.

Is there some other trick I should have used?

Photos attached

Re: 1" threaded copper union leaking

I prefer to use pipe dope rather than teflon tape. And the teflon tape should not be on the seat of the connection. I am assuming you used two good size wrenches to to really tighten the fitting.

However, it may not have been your fault at all. The cheaper fittings bought from a big box store supplied from China have become known for "hit or miss" threading. I have read on many forums frustrated users reporting that the threading on some parts are not machined well enough to allow a tight, leak free fit. It's probably a case of 90% good, 10% bad, but it's the 10% that people take the time to post about.

Re: 1" threaded copper union leaking

Only the seat of the union is intended to provide a seal. The threads are not meant to seal; they are only there to provide a mechanically strong connection. The seats should provide a good seal with just metal-to-metal contact; no compound or tape necessary.

If the union is not sealing, then the seats are not mating properly. As bp21901 says, it may be a poor-quality union.

Re: 1" threaded copper union leaking

I did not use pipe dope - the way I wrapped the teflon tape, it overlapped into the seating area by just a small amount.

After the joint sat a while, the dripping has stopped, now it's just a "cold sweat" of moisture. For now, I'm going to leave it as-is and monitor. Fortunately, as you can see in my pic, I'm not lying on my back under the house to work on it, it's waist-high in an alcove under the stairwell, so it's easy to check on.

Maybe next weekend I'll give the joint another crank with wrenches - I admit I just used channel-locks on the nut. With a bit of re-tourqing it should be OK. I may even open it up and put some pipe dope in there.

Thanks for the advice.

Re: 1" threaded copper union leaking

By the way...

The Union I got from Home Depot is identified with the logo:
Streamline Mueller Industries, Made In USA, Fulton MS

Re: 1" threaded copper union leaking

Wow, you got one made in USA, that may be a museum piece!

I would get a couple pipe wrenches and very firmly, by pushing one and pulling the other, try to get a leeeettle extra snugness out of the union fitting. I would bet that will take care of the drip.

You just have to "persuade" that drip to leave town! :)

Re: 1" threaded copper union leaking

A little pipe dope on the seat may help and a little more torque.

Re: 1" threaded copper union leaking

Well actually what remaining drip there was has gone away. If I wipe my hand across the bottom of the fitting it comes back a little damp, but there isn't enough moisture to even create a drip.

I'll torque it up a little next weekend, if it will budge

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.