# Dielectric unions coming back to bite me.



## Plumbersteve (Jan 25, 2011)

The first time, I questioned myself. "Did I forget to tighten the dielectric on that water heater?" It seemed unlikely. After all, I've put in hundreds of water heaters. Why, all of a sudden, would I leave a dielectric loose? Either way, the dielectric union leaked and ruined the water heater as well as some wood trim and drywall. I took my lashes and henceforth agreed to fill out a checklist each time I installed a water heater that included items like; dielectric unions tight? Three flu screws in each joint? Drip leg on gas? And so on...

A month ago, I installed two water heaters in parallel. That's four dielectrics for those of you keeping score. At the end of the job, I went through my check list and verified each item which included putting pliers on the unions to make sure they were in fact tight. 

Yesterday the customer called and said that the water heater was leaking. So, the boss went out to check it and found that ALL FOUR union nuts were barely more than hand tight. 

Has this happened to any of you? Dielectric unions loosening up after about a month?


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## rwh (Dec 17, 2014)

Dielectrics suck in general. Don't use them


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## Plumbersteve (Jan 25, 2011)

rwh said:


> Dielectrics suck in general. Don't use them



Ok. Are we not worried about corrosion? How do you circumvent the code requirement? What about WH warranty?


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## gear junkie (Jun 20, 2008)

Plumbersteve said:


> Ok. Are we not worried about corrosion? How do you circumvent the code requirement? What about WH warranty?


What corrosion protection?


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## plumber11928 (Feb 18, 2015)

Just wondering if you use thread sealant on the threads. My plumbing mentor back in the day always said to me i'm buying the pipe dope, so use it on anything that has threads. Pipe dope is cheap...Leaks are expensive


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## Cajunhiker (Dec 14, 2009)

Plumbersteve said:


> The first time, I questioned myself. "Did I forget to tighten the dielectric on that water heater?" ... Has this happened to any of you? Dielectric unions loosening up after about a month?


Short answer: No.

Almost sounds like sabotage.

I know this: you have to do something different so you can get a better result. Try switching to a different manufacturer AND as mentioned above, put thread sealant on your threads. If it happens again, it's definitely sabotage.


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## OpenSights (Mar 23, 2015)

I can't say I ever had a "backing off" problem over time with dielectrics in general, though, yeah sometimes heat, cold, expansion, contraction happens. I've had call backs on them, but probably ten times in ten years maybe? I normally buy dielectrics from Builders or Crawford Supply (As it shows on my card), but I did have a run in with bad dielectrics from Ferg's once. One whole box leaked right on install.

I only use 'em because of swap value. Replace the gasket and m/f. Lets just say Apallo style furnace/heater is bad for MI. 3 years max life. 


Dope, think of it as not just a sealer on a thread, but as a lubricant to tighten threads tighter, barring braided supplies of course.


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## Plumbersteve (Jan 25, 2011)

I didn't ask whether or not you used them. I asked if you had trouble with them. 

I do use dope and I tighten them to the right.


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## rwh (Dec 17, 2014)

Dielectrics are junk. They have a rubber washer in them. They are junk just like "terminator" valves, which utilize an o ring. Pipe dope is for pipe threads. Not union faces or threads. Use a good anti seize compound on union threads. Approved for the application, of course. Use plumber's grease on compression joints.


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## Master Mark (Aug 14, 2009)

SS steel Brass Craft connectors on top of the water heater work a lot better than dialectric unions.... 

why do you need dialectric unions when the water ehater already had dialectric nipples installed into the tanks...


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## Blackhawk (Jul 23, 2014)

I use to buy the cheap matco ones and have never once had an issue.

I now install brass female x sweat unions because electric unions corrode in a very short amount of time.


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## OpenSights (Mar 23, 2015)

Some good points. A lot of what I do is more for the inspectors in my area, and some not so much. They like seeing dielectrics, do they do their job? No. Had a conversation with an electrical engineer (Bad word, I know) early on who asked what they were supposed to do. I gave the shpeal of what I was told about electrolysis and different metals taking electrons or what not away from one metal to another... he said; water is a conductor right? So they are not an end to all means.

Now direct contact, brass to cast iron, copper to galvi... they just don't like each other. Sometimes its codes we have to follow. I've been to rentals where I HAD to install dielectrics because the inspector wants them per local code.

They have advantages in an Apollo (State) system when you have to change a heater every 2-3 years.


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## BOBBYTUCSON (Feb 8, 2013)

well , most quality waterheaters come with dilectric nipples already on the the ins/outs ,and i always avoid the dilectric unions alltogether by putting brass couplings and then 8'' brass nipples when i run into galvanized and have to transition. i have found the brass route better performing than those ****ty unions that rely on a paper thin washer in reality. yah its more expensive on the fittings n parts , but unions cause callbacks which our cost of our time is way more expensive.plus , unions dont last long , ive seen them fail within a few short years, which makes customers scratch thier heads as to how trusty we are. now , nomatter what we do , corrosion still wins the war. but i have found that using 8'' brass nips with couplings , which is within code , definitely delays the process better than ****ty unions.

as far as your unions coming loose...thats crazy , this has never happened to me. i dont see how this is possible unless sabotage or maybe pressure build up causing unwind effect but i just dont see how thats enough to undo a plumbers fitting if he is sure he torqued it right. perhaps switch to tru-blu pipe dope or hercules gripp , they have adhesives


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## rwh (Dec 17, 2014)

I know unions are required under most codes on water heaters. They have always seemed kind of pointless to me, unless the house is piped in galvi, and you need them. Copper is easy enough to cut if you are going to the trouble of changing a tank. If you put grip or blu block or any other hard setting dope on them, they may as well not be there.


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## GREENPLUM (Jul 27, 2008)

I only put them on big commercial heaters and don't know why


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## rwh (Dec 17, 2014)

GREENPLUM said:


> I only put them on big commercial heaters and don't know why


That is my point greenplumb. So on a water heater change out, there are unions when you get there. If its a d.e. it will be shot. Even if it looked ok, you wouldn't trust it and replace anyway. A sweat union is cool, but you have to un-sweat one side to reuse it, or make another sweat joint to tie back in. Screwed pipe necessitates a union due to physics. Commonly changed parts are fitted with unions or flanges, I.e. pumps, steam traps, radiator valves, faucets, downstream side of stops, etc. Water heaters I.M.O. need no unions. That is what separates tradesmen from handymen?


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## Fatpat (Nov 1, 2015)

Ditch the dielectric nipples and unions.
Al least 6" of brass and a brass Union and be done with it.

No call backs, no switching gaskets and no corrosion!


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## Ncplumber84 (Dec 30, 2014)

I use brass couplings on top of the nipple.


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## Jessedog11 (Feb 6, 2016)

Use the Nipples that come with the New HWW, In NYC we don't use them at all. Straight Copper x male , new EVER had a problem in 25 Years .


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## Nathan901 (Feb 11, 2012)

The best way of connecting to a heater that I've seen is just a copper male into the tank. 


I've unscrewed so many out of old tanks and the threads look brand new, and no corrosion inside the fitting or tank. 
On installs in residential, it's copper straight to the nipples. 
It's funny, I always do dielectrics on bigger heaters, and don't know why either.


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## Jessedog11 (Feb 6, 2016)

Agree with Nathan901.


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