Bridging over a water pipe dialetric union (for electrical grounding)

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brycenesbitt

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So I have this house with galvanized pipes, to which various grounds are attached.
The main feed from the street was replaced with copper, and the plumber properly installed a dialectric union between the two pipe types.
Naturally the main panel feed connects to the galvanized half, and the complaint is lack of ground.

No new construction is involved, this is a retrofit. If I ask them to bridge the two pipes (regardless of what happens near the main) will I subvert the function of the pipe union?
 
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brycenesbitt said:
So I have this house with galvanized pipes, to which various grounds are attached.
The main feed from the street was replaced with copper, and the plumber properly installed a dialectric union between the two pipe types.
Naturally the main panel feed connects to the galvanized half, and the complaint is lack of ground.

No new construction is involved, this is a retrofit. If I ask them to bridge the two pipes (regardless of what happens near the main) will I subvert the function of the pipe union?
Click to expand...

The purpose of the insulating fitting is to prevent galvanic action between the dissimilar metals on either side of the fitting when current passes through. Bonding around this union shunts the current away from the area of concern, and the insulating fitting is still doing what it was intended to do.
 
Prior to the shunt the galvanic potential will (presumably) not be generated as the metals do not touch.
With a shut the current will flow through the shunt.

Will this shunt eventually create corrosion inside the pipe at each attachment point?

Oct06_JoinCopper-1_size2.jpg


http://www.lifetime-reliability.com...olutions/tip-016-pipe-galvanic-corrosion.html
 
brycenesbitt said:
The question on the table is: does bonding over the union make the problem worse, better, or have no effect?
Click to expand...

No effect, the bonding only allows the piping to be continuously conductive across the dielectric fitting that is used to isolate the two dissimilar metals to prevent galvanic stimulation between the two dissimilar metals.
 
Gregg Harris said:
No effect, the bonding only allows the piping to be continuously conductive across the dielectric fitting that is used to isolate the two dissimilar metals to prevent galvanic stimulation between the two dissimilar metals.
Click to expand...

The difference in electronegativity between the two metals is what causes the corrosion when they are in contact with each other in the presence of moisture.
That same difference allows the two metals to act as the active elements of a battery if they are immersed in an electrolyte.
Ordinary water is not a particularly good electrolyte, so as long there is no direct contact as opposed to an external circuit, the effect will be tolerable.
 
brycenesbitt said:
Prior to the shunt the galvanic potential will (presumably) not be generated as the metals do not touch.
With a shut the current will flow through the shunt.

Will this shunt eventually create corrosion inside the pipe at each attachment point?

Oct06_JoinCopper-1_size2.jpg


http://www.lifetime-reliability.com...olutions/tip-016-pipe-galvanic-corrosion.html
Click to expand...

Would seem to me the bigger problem is an issue of the plumber not the electrician. If we do not bond around this fitting, in many cases there may be incidental bonding around it anyway, outside of direct contact of dissimilar metals, IMO the plumber possibly needs to consider if having mixed metals on same system are a good idea or not, especially if information in your link is valid.
 
I don't think the folks at Wikipedia are any less capable of neologisms. One of the last words at the end of the article is "electronpositivity". I know that is not a word since electrons are negative.:p

At least I hope they are. Otherwise I am kicked out of the 7/11 and have to go in the alley behind the dumpsters.:weeping:
 
ActionDave said:
. One of the last words at the end of the article is "electronpositivity". I know that is not a word since electrons are negative.:p

At least I hope they are. Otherwise I am kicked out of the 7/11 and have to go in the alley behind the dumpsters.:weeping:
Click to expand...

Well, I usually do not make an issue of spelling in posts, but the word used is electropositivity, in which, just like in electronegativity, the "electro" refers in general to electricity rather than to the charge on electrons in any particular material (which is always negative!)

You can keep your key. :)

PS: The single "n" in electro-negativity belongs with "negativity" not with "electron" In electro-positivity there in no "n" at all.
 
GoldDigger said:
It is a real word, its use is just pretty limited to chemists, metallurgists and folks who have to deal with galvanic corrosion a lot. And word freaks of course. :)
http://en.wikipedia.org/wiki/Electronegativity
Click to expand...
Having been a chemist in a former life, I can attest to the correctness of that. There are lists of electronegativity which rank metals according to their ability to wrest electrons from one another, and generally speaking the farther apart two metals are on the list, the worse it is for them to be in contact with each other in the presence of an electrolyte.
 
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ggunn said:
Having been a chemist in a former life, I can attest to the correctness of that. There are lists of electronegativity which rank metals according to their ability to wrest electrons from one another, and generally speaking the farther apart two metals are on the list, the worse it is for them to be in contact with each other in the presence of an electrolyte.
Click to expand...
Unless you are building a battery:) Well maybe not in direct contact in that case either.
 
In researching this I've learned there are TWO types of fittings used in this case:


  1. A traditional dialectric, consisting of some form of plastic insulator between metals.
  2. A brass fitting several inches long. Brass is halfway between copper and steel on a galvanic series, thus you break the large problem into two smaller ones. Presumably this one is actually conductive, though I'd never trust it with all those transitions.

See also http://www.corrosionistforum.com/
Galvanic corrosion is a real multimillion dollar problem... I'm just not clear if I made it worse or better by recommending the jumper.
 
brycenesbitt said:
In researching this I've learned there are TWO types of fittings used in this case:


  1. A traditional dialectric, consisting of some form of plastic insulator between metals.
  2. A brass fitting several inches long. Brass is halfway between copper and steel on a galvanic series, thus you break the large problem into two smaller ones. Presumably this one is actually conductive, though I'd never trust it with all those transitions.

See also http://www.corrosionistforum.com/
Galvanic corrosion is a real multimillion dollar problem... I'm just not clear if I made it worse or better by recommending the jumper.
Click to expand...
Broken link or broken forum....
 
You need to bond around it regardless of opinions.
This is the biggest peeve of mine.
Plumbers repipe or make repairs and leave the ground clamp hanging.
 
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