I just replaced our gas hot water heater. I changed out both water unions and inspected the new ones before soldering to new stubs. The cold stub is a fraction off of plumb to the supply pipe and the hot stub is dead on.
When I filled the water heater I had a teenie leak on the cold side, so I found a little more room to tighten the jamb nut and I believe that's gone. When the hot side pressurized with water it started to leak. I tightened the jamb nut a little more and nothing changed. I gave it one more hard push and now it leaks worse.
I had put teflon tape on the union threads just as a lubricant for tightening.
Also, did I overtighten?
Any ideas on how to fix the leak without desoldering and replacing the new union?
I helped a friend install his water heater with unions. They both leaked. I played with them by tightening them but was not satisfied. I removed them both and didn't use any unions. I've never used unions on any of my water heater replacements.
(Marq1 – I know what you are saying is true, but…)
I have a 1” brass union that had a really slow drip after I installed it. Could not stop it, no way no how. But then I used Teflon tape on the threads with RectorSeal #5 over the tape - and then a no-no - I also put some RectorSeal #5 inside the union itself, so I guess it got down to the mating surfaces (which I know should probably be counterproductive because they are machined to mate with nothing between as you say).
I felt I had nothing to lose by trying that.
But, somehow that stopped the drip – for about 8 years now.
Contrary to what Marq1 is telling you, a dielectric union is not a flared compression fitting. It is 2 flat pieces of metal that mate perfectly, usually with a gasket in between. Just like in this image.
A dielectric union is a little different than just a standard union. Often a standard copper sweat or galvanized union does not have a gasket. Just two parts that mate together.
A dielectric union is for when you are connecting two pipes of dissimilar metals to prevent galvanic action that can cause corrosion.
Marq1 is showing a flared fitting that is used for gas piping with soft copper, not for water.
He said he is sweating, so the pipes are copper, and generally you always want to use a dielectric union when hooking up a hot water heater due to dissimilar metal at the hot water heater connection. If you use a standard union when hooking up a hot water heater you may run into electrolysis problems.
Copper unions, very much like the gas fittings, rely on a metal to metal fit, could even call it a "compression fitting"!
If it's leaking it's defective and there is no sealant, no tape, that will make a difference. Your only option is to torque the threads and hope it seals.
If your issue is with a dielectric union, yes it has a gasket in there and may be the cause but again, sealing the joint between the two halves will have no effect!!
If the op has a standard copper union, that is called a slip union. Just as PJMax said, it is 2 flat surfaces that mate together... no washer... no compression ring. It is not called a "compression" fitting by anyone in the trades.
A dielectric union is basically the same, except the dissimilar metals are separated by non conductors. It is also not a compression fitting.
A copper "compression" union would have 2 compression rings on either side being joined.
Flared fittings are completely different, are called type B compression fittings, and aren't typically used in plumbing, just gas.
The leak stopped. It was a combination of tightening the stub on the water heater (8 inch stub on the heater to an all copper union) a little more to rotate the stub/male side of the union to a different position and using a lot of PTFE pipe dope on the threads to provide lubrication to crank down on the union nut - which I did.
Regarding dielectric: I have all copper to the water heater. I wondered when I attached the threaded fitting on the stub to the plated steel threaded nipples on the heater about dielectric issues. The last water heater went 10 years with the same config and there was only a little corrosion in the old copper stubs that probably was the nipples. (I have to go look at the old water heater nipples before I scrap it.)
So now that I'm leak free, do I have to worry about dielectric corrosion issues? If so, would the dielectric union go right on the water heater without stubs?
IMO, anytime you don't put a dielectric union on a water heater you are taking the chance that you are accelerating the demise of your pipes. If you use them, you generally install one stub on the water heater, then the union between the stub and the copper. As in this video at about 10:00. Whether you use one or not is ultimately up to you. In my mind, they are a no brainer. But as PjMax said, he never uses them. I've seen plenty of pinhole leaks in copper pipes in my area, so I use them. That can be due to dielectric displacement (corrosion) in action.
Many water heaters today come with what the manufacturers call heat trap nipples and some come with what they call dielectric nipples. Regardless, both type nipples are made of steel. I use female threaded dielectric unions on both types that screw right onto the factory installed short nipple extending up from the tank. Never had a leak.
So I followed the advice here and got two dielectric unions. I repiped the cold a couple of days after being advised here. There was a touch of rust already forming in the nipple. I changed the configuration and it was fine immediately. I like it better this way so I really appreciate everyone's help. Thank you!
Yesterday (about a week later) I did the hot side. It had a lot more rust even staining the plastic inside the nipple. I cleaned it up and carefully assembled everything. Immediately it had a slow trickle between the female threaded adapter and the tank nipple - not the jam nut.
Today, I have disassembled and replaced everything three times and still have a slow trickle. The droplet forms and then drops slowly (between the nipple and adapter). I even tried another adapter from an extra union I bought. Also each time, I use even more teflon tape than the prior attempt. And yes I remove the prior tape and clean the nipple.
You can see a droplet in the photo.
The nipple threads are perfect. The female adapter is getting little burs on the internal threads, probably because I am tightening the hell out of it each time.
My main question: how do I fix this now???? FYI - the prior copper fitting I had on the nipple did not leak.
Secondary question: how did rust form so fast? Is the dielectric conduction that good that fast? Can the fact that the plumbing is part of the house's electrical ground contribute to a current that causes a dielectric?
If you are not using a tfe paste that is the entire problem. You don't need to tighten things superhumanly tight if you use paste instead of... or in addition to... teflon tape.
The electrolysis only has to do with dissimilar metals in contact with one another. It's similar to how certain metals get plated. Silver plated... Gold plated. Doesn't take long given the right combination.
You would read the label of the paste you buy, and it will say whether it is "safe for potable water" or not. I'm not going to say yes, when I don't know what product you're going to buy... when it's right on the label. There are probably some that are not.
Quick backstory: I have a basement rambler and for the past several months, I have been noticing a faint odor in certain areas of the house that seemed to be originating somewhere under the stairs. I have switchback stairs with a landing going down to the basement and underneath is a storage area. When I open the folding door to under the stairs, it has a pretty strong smell which I determined has to be coming from the joist channels because they are exposed under there and I took everything out from underneath and found nothing. I originally thought it was a dead smell and was just waiting for it to go away but it has been there for probably 6 months and hasn't changed and the more I go in there, I think it is more of like a stagnant water/sewer smell.
Lately when I go outside the front door (in the picture), I occasionally get a sewage smell depending on the wind. Anyways, yesterday the dishwasher was running and I smelled it more and I leaned down to that vent under the window and could smell it coming from there. I get a pretty faint smell from that vent with no water running but when the water starts running, it comes on stronger. That vent is right beneath the floor level of the main floor so it must be venting the joist channels. The kitchen sink is centered under the window and you can see the roof vent and I know where the pipe is in the basement (it goes straight down inside the wall and into the floor) and from where I measured, it appears that it is a straight shot from the vent all the way down into the basement and the sink drain must go over horizontally into it somewhere (I have the yellow line drawn where I believe the drain pipe is likely run, the yellow circle above the hose bib would be where the drain goes into the wall in the undersink photo). I can definitely hear the water running well when I get down near that grate just like you would hear water running through a pipe in an exposed wall. Where could this smell be coming from? There can't be a leak in this pipe anywhere or else I would have water in the basement or at least leaking through the ceiling or walls down below. What are your thoughts?
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Hi, I installed a utility sink in my garage on the other side of the wall from my laundry room. The drain and p-trap for the washing machine is in the wall behind and just to the left of the utility sink. Is there any reason I couldn't tee the drain for the utility sink into the horizontal pipe for the washing machine above the p-trap? See market up photo attached. Thank you.
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05-29-21, 03:50 PM
Brand New Leaky Copper Union - Help Please
If so, would the dielectric union go right on the water heater without stubs?
If so, would the dielectric union go right on the water heater without stubs?
