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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.

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

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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.

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Discussion Starter #23
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.

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

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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????
 

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philosopher and statesmen
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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 .....

 

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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....
 

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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....

 

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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....

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....
 

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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.
 

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

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philosopher and statesmen
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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.....



 

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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.


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philosopher and statesmen
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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.


.


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??


 

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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??
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.
 

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......
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??



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




.
 
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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.....



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..
 

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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.
 

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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...
 

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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 .
 
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