Water Heater Nipple Weeping at Union Connector- Tried but Still Weeping. Tips and Ideas?

HandyFS · February 28

I had to replace the dip tube on a Weil Mclain indirect and the cold water supply nipple has a small break in the threads about 1/2 way down and is causing the union connection to weep just a little bit once pressurized. This water heater has welded-in nipples, so I can't swap them out, unfortunately.

I tried a few combinations of spool wick, Teflon tape, and regular pipe dope without success. Tried separately, and in different combinations. A very slow weep, but weeping nonetheless.

I have seen some mentions in past threads, and the web of using Blue Block dope, different locking thread sealants, lamp wick/spool wick, and beyond.

I had another HVAC guy put a new union on since it was leaking before and he took a few tries but got it to stop with Teflon tape, but I'm not having the same luck.

Any suggestions? I was thinking maybe I'd change up the union and replace it with a supply hose that has the nut/gasket on the top side of the nipple so it may rely less on the threads and that rubber gasket may help solve the issue. Is this a better plan than to try to keep wrenching around with the nipple? This seems promising.

I've tried a few different combinations and I can get it 99.5% to stop other than a minor weep, but that last little bit must be stopped.

I appreciate everyone's help on such a rookie issue.

Jamie Hall · February 28

Problem. First off, those aren't union threads -- they're NPT. Even with that nick, though, they would seal -- with an NPT fitting and generous dope or tape. Or both.

But.

Even if it were a union that your are playing with there, it wouldn't seal, as unions aren't designed to take up the angular misalignment between that fitting and your pipes above it. No hope.

You are best off replacing it with the flex hose and rubber gasket arrangement you mention.

HandyFS · February 28

Jamie Hall said:
Problem. First off, those aren't union threads -- they're NPT. Even with that nick, though, they would seal -- with an NPT fitting and generous dope or tape. Or both.

But.

Even if it were a union that your are playing with there, it wouldn't seal, as unions aren't designed to take up the angular misalignment between that fitting and your pipes above it. No hope.

You are best off replacing it with the flex hose and rubber gasket arrangement you mention.

Thanks for the feedback. This was an FIP so almost sure that was an NPT thread, so I figured it was compatible:
https://www.homedepot.com/p/Everbilt-3-4-in-Galvanized-Steel-FIP-x-Sweat-Dielectric-Union-FSU-HDLFDU-34/311317713

Maybe I'm explaining it wrong, but the leak is where the bottom side of the union adapter threads onto the nipple. The top union part is fine, its where the nipple and bottom side of the union are mating with the male nipple threads, and female threads of the union connection.

I'm going to give those flex hoses a shot, seems like its my best shot. Thanks for the vote to give these a go.

I am feeling a bit defeated though, I felt like I should be able to get this one to stop leaking. I may try Lamp Wick (Thicker) instead of the Spool Wick (Thinner) I was using just to see at this point. If that doesn't cut it, a new set of connector hoses hopefully seals the deal, and the leak asap.

Larry Weingarten · February 28

Hi, Is there any way to straighten the pipe above the union? That tilt, along with the thin gasket in the union, and the strain on the fitting are a recipe for a leak. Also there was another thread recently on everyone's preferences for making a leak-proof threaded connection. Maybe you'll find some ideas there. For what it's worth, with metal threads, I just use at least six turns of teflon (depending on the thickness of the teflon) on that size pipe and almost never have leaks.

Yours, Larry

Mustangman · February 28

I've been in this trade for 47 years so I guess I am an old timer. The old timers when I was young, would use lead wool. Probably impossible to find unless you have a plumber who will sell you some. The lead in this form was longer strings of lead.. they wound it in the threads front to back. the on the starter end a pipe dope.. only cover the first 2 threads with dope. I do the same with tape and dope.. just the first few threads. It rolls back and looks professional.
Have you tried the grey teflon that is for stainless?

EBEBRATT-Ed · February 28

It may not be leaking from the threads. As Larry mentioned the pipe is crooked and the water could be running down from that

Jamie Hall · February 28

You didn't explain it wrong -- it's just that that is where the leak is appearing. As @Larry Weingarten said, so long as that pipe above is crooked like that, you'll never get that to seal.

KC_Jones · February 28

Where is the leak at? I highlighted in red where it would have to be if those pipe threads are leaking. If it's a different location it is due to the misalignment of the union with the pipes above.

mattmia2 · February 28

I bet it is actually leaking at the bottom of the union and running down so it looks like it is the threads. Everyone has some leaks sometimes.

SuperTech · February 28

I'd try using Leak Lock with Teflon tape. Let it cure and dry out before applying water pressure to it. That's worked for me in the past when dealing with damaged threads. I would also get rid of the dielectric union and use a brass 3/4" coupling instead, much less potential for leakage it will provide the same dielectric separation.

HandyFS · February 28

KC_Jones said:
Where is the leak at? I highlighted in red where it would have to be if those pipe threads are leaking. If it's a different location it is due to the misalignment of the union with the pipes above.

Yes, this is where it is leaking, on the nipple threads where the bottom part of the union mates to the water heater. The top is crooked, but that part does not leak. Not sure why the last guy installed it like that, but it hasn't leaked up top so I haven't redone it.

The leak is where your red line is. Thanks for helping me clarify.

HandyFS · February 28

SuperTech said:
I'd try using Leak Lock with Teflon tape. Let it cure and dry out before applying water pressure to it. That's worked for me in the past when dealing with damaged threads. I would also get rid of the dielectric union and use a brass 3/4" coupling instead, much less potential for leakage it will provide the same dielectric separation.

Is something like this ideal?
https://www.supplyhouse.com/Supco-HS10001-Highside-Leak-Lock-Pipe-Joint-Sealant-Tube-1-1-3-oz

What type of connection would you use instead coming off the nipple and the 3/4 coupling? Would you then go from the 3/4 brass coupling over to threaded copper and onto the supply line? It looks like I'll probably reworking things at this point anyhow, so any tips on connections from the supply line to the inlet nipple appreciated.

SuperTech · February 28

That's the stuff I use. Yes I typically use a 3/4" brass tee on the cold water nipple of the tank and use brass nipples and fittings to connect an expansion tank if needed. If I don't need to install an expansion tank I use a brass coupling and connect the water pipes with a 3/4" copper male adapter.

pedmec · February 29

Why are you using a dielectric union on a dielectric nipple? get rid of the dielectric union and use a propress x female union with a ground joint face. the damage thread is so far down on the nipple it's not coming into play.

Jamie Hall · February 29

HandyFS said:

KC_Jones said:
Where is the leak at? I highlighted in red where it would have to be if those pipe threads are leaking. If it's a different location it is due to the misalignment of the union with the pipes above.

Yes, this is where it is leaking, on the nipple threads where the bottom part of the union mates to the water heater. The top is crooked, but that part does not leak. Not sure why the last guy installed it like that, but it hasn't leaked up top so I haven't redone it.

The leak is where your red line is. Thanks for helping me clarify.

Let me try again. The red line is where the leak appears. That's fine. That's not where the leak is. That union arrangement, with the misalignment, is never going to seal and not leak. The water is moving down inside the union nut (which it will) and you see it at the red line.

hot_rod · February 29

That looks like a stainless nipple, which makes sense if it is a stainless indirect. And a dip tube inside.

stainless can be tricky to seal, there us a specific tape and pipe dope for stainless that works well

If you can get it dry, Loctite a stainless coupling onto that bad thread

Water Heater Nipple Weeping at Union Connector- Tried but Still Weeping. Tips and Ideas?

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