# To dielectric union or not to dielectric union



## Nazareth (Sep 30, 2017)

I have always seen the argument back and forth between whether or not you should put a dielectric union on the nipples for a w/h even though the majority of w/hs have dielectric nipples already installed. 

I've always seemed to have issues with dielectric unions clogging up with junk over time, but I'm indecisive on whether or not I should be using the unions at all, or just threading an FIP adaptor on and calling it a day


----------



## OpenSights (Mar 23, 2015)

Any master I’ve worked for uses them on heaters, so I do. I do see an advantage in some apartment complexes for a simple swap out. Do I believe they really make a difference? Nope. The inspectors like to see them. F’in overloads! I really think they only make a difference when connecting to old galvi.


----------



## ShtRnsdownhill (Jan 13, 2016)

OpenSights said:


> Any master I’ve worked for uses them on heaters, so I do. I do see an advantage in some apartment complexes for a simple swap out. Do I believe they really make a difference? Nope. The inspectors like to see them. F’in overloads! I really think they only make a difference when connecting to old galvi.


I make nothing easy for the next person..as that next person could be some hack that you made it easy for them to do plumbing work...
whatever the heater comes with is what they get, I never added dielectric unions to anything...
the gas meters that are supplied by the gas company have dielectric unions as an integral part of the meter bars they give out...


----------



## Debo22 (Feb 15, 2015)

Here in earthquake part of the country we use flex lines


----------



## Tango (Jan 13, 2018)

Brass adapter here. Brass is a neutral metal so no corrosion. Never seen a dialectric union on a water heater in my life.


----------



## The Dane (Feb 19, 2015)

My boss claims to have seen the copper female adapters corrode out and leak badly. For that reason he wanted us to switch to using dielectric unions (my bad for telling him about them when he complained about the copper females). Around here there are never dielectric unions on the old heaters but some times a regular union. That union is worthless anyway as all new heaters are taller than the old ones. I hate dielectric unions for the reason that they clog up. The few I have taken out always look like these pictures I took. I use a brass female adapter.









Sent from my SM-G970U using Tapatalk


----------



## GAN (Jul 10, 2012)

Yep brass unions, wont' corrode up. Never copper on the galvanized threads on a heater galvanic reaction will take it's toll.


----------



## canuck92 (Apr 1, 2016)

If you install an HTP tank it says right on it " do not use dialetric unions it voids warrany".
Then i unthreaded them an went an bought 1-1/2 bar stock females lol


----------



## justme (Jul 4, 2012)

canuck92 said:


> If you install an HTP tank it says right on it " do not use dialetric unions it voids warrany".
> Then i unthreaded them an went an bought 1-1/2 bar stock females lol



You're corrrect the HTP stainless steel tanks require you to install copper directly to the tank. Di-electric unions void the tank warranty.


----------



## Nazareth (Sep 30, 2017)

Tango said:


> Brass adapter here. Brass is a neutral metal so no corrosion. Never seen a dialectric union on a water heater in my life.


You see I've heard people argue that, too.

I've heard most of my mentors say you need at minimum 6" of brass, but then people here say that a simple brass FIP will work, or a brass union.

Does the 6" rule really matter that much?


----------



## The Dane (Feb 19, 2015)

I'm pretty sure my UPC code states that water heaters must be connected with eighter a dielectric union or 6" of brass. I hate dielectric unions so that's a no for me. Now with the water heaters all having dielectric nipples these days I am good with just the brass fip adapter.

Sent from my SM-G970U using Tapatalk


----------



## czplumbing (Nov 24, 2014)

I hate them never use them


----------



## czplumbing (Nov 24, 2014)

I hate them never use them . they seem to cause more issues


----------



## Tango (Jan 13, 2018)

Nazareth said:


> You see I've heard people argue that, too.
> 
> I've heard most of my mentors say you need at minimum 6" of brass, but then people here say that a simple brass FIP will work, or a brass union.
> 
> Does the 6" rule really matter that much?


Never heard of that 6" thing. 3/4" Female adapter and copper, That's all I've seen in 26 years. 

Nowadays brass adapter and straight to pex.


----------



## The Dane (Feb 19, 2015)

Tango said:


> Never heard of that 6" thing. 3/4" Female adapter and copper, That's all I've seen in 26 years.
> 
> 
> 
> Nowadays brass adapter and straight to pex.


Straight to pex hmm. Here UPC and most manufactures require 18" of ridgid metal tubing before going to any plastic piping.

Sent from my SM-G970U using Tapatalk


----------



## czplumbing (Nov 24, 2014)

The Dane said:


> Straight to pex hmm. Here UPC and most manufactures require 18" of ridgid metal tubing before going to any plastic piping.
> 
> Sent from my SM-G970U using Tapatalk


 why? once you go pex it is what it is who made that law?


----------



## The Dane (Feb 19, 2015)

czplumbing said:


> why? once you go pex it is what it is who made that law?


I believe its something to do with in case the tank overheats then that first bit of metal piping can give off some of the heat in the first 18" so the heat from the tank rising up will cool down a little before hitting the plastic pipe. Honestly no one I know of has an answer but it is the code.

Sent from my SM-G970U using Tapatalk


----------



## Tango (Jan 13, 2018)

The Dane said:


> Straight to pex hmm. Here UPC and most manufactures require 18" of ridgid metal tubing before going to any plastic piping.
> 
> Sent from my SM-G970U using Tapatalk


Here this is code. Water heater rental company. :vs_laugh:


.


----------



## Tango (Jan 13, 2018)

The Dane said:


> Straight to pex hmm. Here UPC and most manufactures require 18" of ridgid metal tubing before going to any plastic piping.
> 
> Sent from my SM-G970U using Tapatalk





czplumbing said:


> why? once you go pex it is what it is who made that law?


Direct pex or poly-B for the last 30 years, no issue that I've heard of and code for us.


----------



## Debo22 (Feb 15, 2015)

Nazareth said:


> You see I've heard people argue that, too.
> 
> I've heard most of my mentors say you need at minimum 6" of brass, but then people here say that a simple brass FIP will work, or a brass union.
> 
> Does the 6" rule really matter that much?


The minimum 6” of brass is between galvanized pipe and copper to prevent electrolysis. They’re probably thinking it’s the same on water heater nipples.


----------



## Debo22 (Feb 15, 2015)

The Dane said:


> I believe its something to do with in case the tank overheats then that first bit of metal piping can give off some of the heat in the first 18" so the heat from the tank rising up will cool down a little before hitting the plastic pipe. Honestly no one I know of has an answer but it is the code.
> 
> Sent from my SM-G970U using Tapatalk


I thought it was only for gas water heaters because it would be too close to the flue and draft diverter.


----------



## The Dane (Feb 19, 2015)

Debo22 said:


> I thought it was only for gas water heaters because it would be too close to the flue and draft diverter.


Maybe your right and its only on gas heaters. I dont have my code book here at home. I just remember the 18" and around here its the standard on all heaters. I have rarely seen one with pex directly to the heater.

Sent from my SM-G970U using Tapatalk


----------



## Nazareth (Sep 30, 2017)

Debo22 said:


> The Dane said:
> 
> 
> > I believe its something to do with in case the tank overheats then that first bit of metal piping can give off some of the heat in the first 18" so the heat from the tank rising up will cool down a little before hitting the plastic pipe. Honestly no one I know of has an answer but it is the code.
> ...


I've seen pex become damaged from being pressed up against a hot flue for a few years, I've always assumed the 18" law is for preventing that kind of stuff


----------



## czplumbing (Nov 24, 2014)

ShtRnsdownhill said:


> I make nothing easy for the next person..as that next person could be some hack that you made it easy for them to do plumbing work...
> whatever the heater comes with is what they get, I never added dielectric unions to anything...
> the gas meters that are supplied by the gas company have dielectric unions as an integral part of the meter bars they give out...


 National Grid always wanted an insulated coupling by meter for any transitions going into ground and NOW they want one by equipment it is connecting to "two Insulated unions" for what????


----------



## Master Mark (Aug 14, 2009)

The Rheem and bradford white already come with dialectric nipples installed on the tank...... 

I dont use them because the flex lines are basically dialectric connectors and if you look at the female connectors the washer and plastic ferrull under the nut into a dialectric fitting.... the flex line breaks the connection to the heater at both ends of the connections... 

better grounding of the whole electrical system is the only way to keep the heater from getting eaten alive .....


----------



## ShtRnsdownhill (Jan 13, 2016)

czplumbing said:


> National Grid always wanted an insulated coupling by meter for any transitions going into ground and NOW they want one by equipment it is connecting to "two Insulated unions" for what????


im thinking with all the electronics and computers in todays equipment, any electric current that may hit a gas line will fry the heating equipment....just like a lightening strike on your tv, computer and other electronics...
so the dielectric union offers a little protection from that..
thats my guess....


----------



## Master Mark (Aug 14, 2009)

ShtRnsdownhill said:


> im thinking with all the electronics and computers in todays equipment, any electric current that may hit a gas line will fry the heating equipment....just like a lightening strike on your tv, computer and other electronics...
> so the dielectric union offers a little protection from that..
> thats my guess....



I just went the extra mile and grounded a plumbing system with some copper and jumper connectors on a Rheem heater I installed 4 years ago.... I installed everythign properly at that time with flex connectors, and a thermal expansion tank but it still only lasted 4 years.... 

the hot side dialectric nipple on the heater was badly corroded due to the electrolysis that was going on with everything trying to ground itself through the heater...


upon closer inspection of the house I found that the whole system lost its ground because the hard line in the home was connected to a water softener with plastic john gest fittings which broke the secondary ground to the city water main... The ground in the home was only grounded on the soft side of the system.....

I also to the fellow that he might want a better grounding wire at the breaker box just to be sure it was still in good condition too 

If the house is not grounded properly, then everything in the home has to ground itself somewhere which is gonna be into the heater.....

Upon further thought, I probably should have also ran a ground to the gas line on the water heater and back to the main ground on the soft side of the system because that is probably what all the current in the home was attempting to ground itself through....


----------



## ShtRnsdownhill (Jan 13, 2016)

Master Mark said:


> I just went the extra mile and grounded a plumbing system with some copper and jumper connectors on a Rheem heater I installed 4 years ago.... I installed everythign properly at that time with flex connectors, and a thermal expansion tank but it still only lasted 4 years....
> 
> the hot side dialectric nipple on the heater was badly corroded due to the electrolysis that was going on with everything trying to ground itself through the heater...
> 
> ...


so if you ran pex to the heater and put a dielectric union on the gas line, the water heater is now insulated from any current or ground issues....


----------



## OpenSights (Mar 23, 2015)

ShtRnsdownhill said:


> I make nothing easy for the next person..as that next person could be some hack that you made it easy for them to do plumbing work...
> whatever the heater comes with is what they get, I never added dielectric unions to anything...
> the gas meters that are supplied by the gas company have dielectric unions as an integral part of the meter bars they give out...


There was a few years where I had 4 apartment complexes that used the heaters as the furnace. Not a bad idea for the southern states, but not for the north! State I believe was the brand. Each heater would only last a year or two so the chances of us swapping it out again was pretty good.

Other than that, I don’t see the advantage. Just one more thing to fail.


----------



## OpenSights (Mar 23, 2015)

I believe code here is 12” copper and nothing “flammable” (including PEX) within 6” of a conventional vent. 12” copper for electric heaters too.


----------



## Master Mark (Aug 14, 2009)

ShtRnsdownhill said:


> so if you ran pex to the heater and put a dielectric union on the gas line, the water heater is now insulated from any current or ground issues....




Never heard of a dialectric gas union before.... did you just pull that idea out of your ass or is that a real thing ??:biggrin:

Grounding the system with all plastic plumbing should be the electricians problem... 
If I were the electrican I would probably double ground the home in front and in back or do something to that affect..... They are making the electricans ground the gas lines in our state due to lightening strikes and other issues with the ss ward flex stuff....... 

I see it all the time where they run a ground line to the copper pipes coming off the heater but it switches to pex a few feet upwards... I think its a joke to do this..... They dont know what they are doing but just doing what they are told to do

I am sure many plumbers have found copper water lines in homes that were literally as thin as a beer can due to the currents that are passing through them and thinning them out over the years.......

I have also driven--installed a ground rod and clamps to the copper into someone's basement floor on one job where they had pex coming into the home for the main water service and that heater ate all the currents in the home....... that heater lasted a few years and leaked.... 

Now they are my little experiment to see how long it lasts....

Most electricians think I am full of shi/ when I tell them the home needs to be grounded better and really dont understand what is going on.....


----------



## OpenSights (Mar 23, 2015)

Master Mark said:


> Never heard of a dialectric gas union before.... did you just pull that idea out of your ass or is that a real thing ??:biggrin:


:vs_laugh::vs_laugh::vs_laugh::vs_laugh::vs_laugh:


----------



## skoronesa (Oct 27, 2015)

Master Mark said:


> .....
> I am sure many plumbers have found copper water lines in homes that were literally as thin as a beer can due to the currents that are passing through them and thinning them out over the years...........



I have not found this and *in my experience copper rotting out has been a water quality issue* 99% of the time when the install is to modern code. I have heard of one or two houses where the wiring was messed up, but that's it.

*When we get pinholing or thinning it's acidic water. *The solution is a neutralizer. We use a special mix of neutralizer from watersoft that must be replenished every year or so. I have also seen neutralizers which are little more than sand filter chambers but with limestone instead. If you don't mind hard water or already have a softener seems like a good idea to me.

I have thus far neglected to chime in on the issue of dielectric unions because again, it appears to me to be a water quality issue more so than anything else, none of us are chemists, and many of us seem to have difficulty grasping the basic principles of the sciences. 


The idea behind a dielectric union is that the water heater can act like a battery cell aka galvanic cell. *Any two different metals will create a potential when separated by an electrolyte solution such as potable water. Some of you have said that brass is "neutral" and this is not true. *Just like a car battery if the terminals are connected than the lead plates inside will undergo electrolysis. The same is true of a water heater.

*Dielectric nipples are not dielectric in the same way as the unions and therefore one does not mean you may forgo the use of the other. *


Before any of you mix it in as well, I feel I should mention that the anode rod is another completely separate issue.


.


----------



## Master Mark (Aug 14, 2009)

skoronesa said:


> I have not found this and *in my experience copper rotting out has been a water quality issue* 99% of the time when the install is to modern code. I have heard of one or two houses where the wiring was messed up, but that's it.
> 
> *When we get pinholing or thinning it's acidic water. *The solution is a neutralizer. We use a special mix of neutralizer from watersoft that must be replenished every year or so. I have also seen neutralizers which are little more than sand filter chambers but with limestone instead. If you don't mind hard water or already have a softener seems like a good idea to me.
> 
> ...




Thanks for that information..... very informative

I still have never run across a dielectric gas union unless perhaps the unions out at the gas meter are dielectric?? 

All that you have talked about is true and I think that many times its a mixture and combination of things that fry out the heaters....

very high water pressure, acidity in the water, sodium in the water from the softener and grounding of the plumbing system , small mag rods in the heaters....
.


'I have taken heater lines apart and got a small spark across them before and found that the copper pipe was thinned down to nothing...


In our region Bradford White heaters dont last their warranty if their is a water softener in the system.... and they last 3 times longer without soft water...... So perhaps that is a combination of sodium in the water and poor grounding of the system...??
.


to quote you
Dielectric nipples are not dielectric in the same way as the unions and therefore one does not mean you may forgo the use of the other..... 

so how about the flex copper and SS flex lines with the dialectric ends on them ....??
Do you think that they count as a dialectric union??


----------



## OpenSights (Mar 23, 2015)

Master Mark said:


> Thanks for that information..... very informative
> 
> I still have never run across a dielectric gas union unless perhaps the unions out at the gas meter are dielectric??
> 
> ...


When I left that POS plumbing company in California I hired into a very small shop that did “cathodic” protection, IIRC. The opener had his master’s in electrical engineering and electrical engineering. He developed a system that would add so many PPM of a chemical, or “product” to the water lines that would coat the inside of the copper lines. We’d go around to a bunch of apartment complexes all over SoCal. It really worked well stopping pinhole leaks.

I think you’re right about a combination of reasons. We get pinhole leaks here, but not what I experienced in California! Out there they have really high water pressure, so high you have to install regulators in homes.

Out here we have water towers, so we don’t have pressure issues, other than galvi closing off.

We have a house on the north side where their heater leaks from the tank every three years along with a pinhole here and there. They’re on a well and softener, we’ve had the water tested and nothing terribly out of wack.


----------



## skoronesa (Oct 27, 2015)

Master Mark said:


> ......
> to quote you
> Dielectric nipples are not dielectric in the same way as the unions and therefore one does not mean you may forgo the use of the other.....
> 
> ...





*As for the softeners, saltwater corrodes steel quickly when oxygen is present, perhaps the softeners aren't properly back washing.*


Dielectric is a technical term which just means electrically insulating. For instance, romex generally has a rating of 600v. That rating means they guarantee the insulation will have a dielectric resistance of at least 600v. Electricity is like magnetism in that it can attract even through materials.



Dielectric nipples just have a plastic sleeve to prevent the nipples from corroding shut. The plastic sleeve electrically isolates the interior of the nipple from the water passing through.


Dielectric unions have two plastic/rubber washers which do not allow the piping to be connected to the water heater. The copper and braided flex lines still have a direct connection through the nut which screws onto the nipple. *Dielectric unions break that connection with the hard plastic stepped washer between the union nut and the inlet side.*


The thing that's always bothered me about dielectric unions is that you're essentially creating a capacitor. A capacitor is a voltage potential across a dielectric material with an electrolyte solution which can flow through the dielectric. The dielectric unions are to prevent you from making a battery cell, but this is the same reason you're essentially making a capacitor. Turning the water heater into a capacitor isn't really an issue *so long as you don't have any stray dc voltages existing between the hot/cold side and ground. This can be eliminated by grounding all parts of the system which you have done and is really the best thing you can do.*
*
*
*The anode rod aka "sacrificial anode" intentionally creates a battery cell aka galvanic potential which will corrode the anode rod instead of the steel.* Even with no galvanic potential in the system at all the steel tank will corrode because that's what happens when you have water and oxygen on steel. Almost all of your water is going to have some dissolved oxygen. The anode rod tries to pull the oxygen out of the water before it can get to the steel. *I can't for the life of me find it referenced right now but the anode creates something like a 20mv voltage potential.*


Here's a good site I found that explains a lot of this in detail.


https://www.hot-water-heaters-reviews.com/anode-rod.html




.


----------



## ShtRnsdownhill (Jan 13, 2016)

Master Mark said:


> Never heard of a dialectric gas union before.... did you just pull that idea out of your ass or is that a real thing ??:biggrin:
> 
> Grounding the system with all plastic plumbing should be the electricians problem...
> If I were the electrican I would probably double ground the home in front and in back or do something to that affect..... They are making the electricans ground the gas lines in our state due to lightening strikes and other issues with the ss ward flex stuff.......
> ...


yes they exist..if I pulled it out of my azz it better be dam well corrosion proof...:vs_laugh::vs_laugh::vs_laugh:

the gas utility has been using them since I started doing plumbing on the outside meter sets so any stray voltage in the soil doesnt cause issues with inside gas lines...
and to protect the under ground gas lines they use cathodic protection....for corrosion..
and since im on an island surrounded by salt water, and close to the shores, we have issues with pin holes in copper water mains from electric current in the ground, the salt makes it much worse than say a clay soil in middle America or the mountains...all we have is sand when you dig past the top soil..


----------



## Dontbitenails (Oct 16, 2020)

I only use brass 7/8" compression X 3/4" FIP adapters on top of water heater. Serves as both union and separates copper/ galvanized.


----------



## ShtRnsdownhill (Jan 13, 2016)

Dontbitenails said:


> I only use brass 7/8" compression X 3/4" FIP adapters on top of water heater. Serves as both union and separates copper/ galvanized.


why? the heat cool cycles can loosen up the compression fitting,mechanical fittings on anything that goes though heat and cooling cycles have the disadvantage of loosening up over time and causing problems...so why add a risk when you dont have to.. and why make it easy for the next guy /hack to change it out...
I only use male or female copper adapters and solder it all together...no chance of leaks...


----------



## Dontbitenails (Oct 16, 2020)

ShtRnsdownhill said:


> why? the heat cool cycles can loosen up the compression fitting,mechanical fittings on anything that goes though heat and cooling cycles have the disadvantage of loosening up over time and causing problems...so why add a risk when you dont have to.. and why make it easy for the next guy /hack to change it out...
> I only use male or female copper adapters and solder it all together...no chance of leaks...


Never had one leak due to temp swings causing fitting to expand and contract . Ran across some crappy fittings ( Asia ) but they only leaked at install . Sourced domestic fittings and have never seen a problem since . Code calls for unions and I do not care what union is on there any DIY will have issues . I cant remember a water heater replacement where you could swap one out easy peasy with only breaking unions apart . Manufactures constantly change sizes due to efficiency standards so very rarely is the new one the same as the existing . I always install a new lever ball valve and expansion tank ( where applicable ) on a WH exchange . Need something between copper and galvanized and brass is the perfect material .


----------



## skoronesa (Oct 27, 2015)

In the following video he specifically talks about dielectric unions, granted he references their use for gas lines but the same can happen with your water heater and the incoming cold water line.


----------



## sparky (Jan 8, 2014)

Nazareth said:


> You see I've heard people argue that, too.
> 
> I've heard most of my mentors say you need at minimum 6" of brass, but then people here say that a simple brass FIP will work, or a brass union.
> 
> Does the 6" rule really matter that much?


The 6" rule they were talking about women and their minimum lololololo


----------



## Tango (Jan 13, 2018)

Here's what happen on most water heaters with brass adapters, they get clogged up. This is about 8-10 years


----------



## Debo22 (Feb 15, 2015)

It happens with flex lines too


----------



## Nazareth (Sep 30, 2017)

Really makes you wonder if we're sitting here trying to figure out a problem that there really isn't a solution to. I understand electrolysis and all that, but clearly the methods that have been attempted in the past to remedy this only amounted to a bunch of crap


----------



## skoronesa (Oct 27, 2015)

Nazareth said:


> Really makes you wonder if we're sitting here trying to figure out a problem that there really isn't a solution to. I understand electrolysis and all that, but clearly the methods that have been attempted in the past to remedy this only amounted to a bunch of crap


I think you should just install it per manufacturers instructions with the dielectric unions and if it fails before end of warranty make sure they pro rate and maybe try to get some labor compensation.

Also, the bottom drain should be purged regularly and the anode checked every couple years. If the bottom drain is a pos than sell them a nipple and a ball valve and explain the benefits to them.


----------

