copper water pipe as primary ground, is this a thing

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FREEBALL

Senior Member
Location
york pa usa
I was told today that the copper waterpipe that travels some 50ft in the ground is not considered a primary ground but a part of the grounding electrode system when incorporated with ground rods ok I understand the gec concept but i was always taught back in the day the waterpipe is the main ground because it is in the earth the deepest and furthest. I always put 2 rods in so this is not the question, i was told today that the waterpipe is not considered primary gec but part of the gec system. any insight
 
There is no such thing as a primary electrode in the NEC. All qualified electrodes present at the structure are required to be part of the GES. The metal water pipe buried for 10' or more is an electrode so it must be used as part of the GES. It is also required to be supplemented, typically by installing ground rods or a CEE is one exists.
 
Technically, there is no such thing as a "primary ground", all grounding electrodes are part of the grounding electrode system.

However, your understanding that scientifically the water pipe has a way smaller resistance to ground than the ground rods do is correct also, it is a far more "effective" (notice the air quotes) grounding electrode. Some of them go for miles and are bonded to everyone else's ground rods etc, so they have a very good connection to the earth.

What the code says is that all electrodes present at a structure must be bonded together to form the grounding electrode system (250.50). If there is rebar in the footing, it must be bonded to the system. If there is metal water pipe in the earth, it must be bonded to the system. If random ground rods are driven around, they must be bonded to the system.

A lot of electrical contractors fail service replacement inspections because they drive two ground rods and think they are done, without bonding to the metal water pipe. That is not correct, if the pipe is there, you have to bond to it.

Obviously, water pipe electrodes need to be supplemented with ground rods or similar per NEC
 
What are you supposed to do with abandoned underground piping. Like in an old plant that went to something that doesn't even exist anymore.

Probably cut it off where it penetrates the wall would be the best. But I've seen a lot of that that was just cut in the easiest spot. I don't think I ever saw abandoned piping bonded
 
Joethemechanic said:
What are you supposed to do with abandoned underground piping. Like in an old plant that went to something that doesn't even exist anymore.

Probably cut it off where it penetrates the wall would be the best. But I've seen a lot of that that was just cut in the easiest spot. I don't think I ever saw abandoned piping bonded
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If it’s abandoned, it’s no longer a “water pipeline” and doesn’t qualify as a grounding electrode. It would only need to be bonded if it’s likely to become energized.
 
Joethemechanic said:
What are you supposed to do with abandoned underground piping. Like in an old plant that went to something that doesn't even exist anymore.

Probably cut it off where it penetrates the wall would be the best. But I've seen a lot of that that was just cut in the easiest spot. I don't think I ever saw abandoned piping bonded
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I just got a new copper water line at my home to replace the old one. Bonded the new one, but left the bond on the old one. Why not? But I agree it is not a "water line" if it is abandoned.

Mark
 
NEC Inspector said:
Technically, there is no such thing as a "primary ground", all grounding electrodes are part of the grounding electrode system.
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Are you working on a telecommunications building or datacenter ? The only time I have herd the term 'primary grounding electrode' is in telcom standards.
 
NEC Inspector said:
Technically, there is no such thing as a "primary ground", all grounding electrodes are part of the grounding electrode system.

However, your understanding that scientifically the water pipe has a way smaller resistance to ground than the ground rods do is correct also, it is a far more "effective" (notice the air quotes) grounding electrode. Some of them go for miles and are bonded to everyone else's ground rods etc, so they have a very good connection to the earth.

What the code says is that all electrodes present at a structure must be bonded together to form the grounding electrode system (250.50). If there is rebar in the footing, it must be bonded to the system. If there is metal water pipe in the earth, it must be bonded to the system. If random ground rods are driven around, they must be bonded to the system.

A lot of electrical contractors fail service replacement inspections because they drive two ground rods and think they are done, without bonding to the metal water pipe. That is not correct, if the pipe is there, you have to bond to it.

Obviously, water pipe electrodes need to be supplemented with ground rods or similar per NEC
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Infinity
thanks now one more question which i am now curious about, When installing a ground rod for the service I was told yesterday that as long as i have the water pipe grounded i only need 1 ground rod. But It says in the code that when installing a ground rod you must also refer to the ground rod rules which state you need less than 25 ohms so we usually drive 2 six or more apart and call it a day I was actually told a long time ago maybe 15 years that we need 2 ground rods regardless in the event the copper underground were to be replaced by plastic. I will still always drive 2 but just wanted some clarification. Thankyou and be safe
 
FREEBALL said:
Infinity
thanks now one more question which i am now curious about, When installing a ground rod for the service I was told yesterday that as long as i have the water pipe grounded i only need 1 ground rod. But It says in the code that when installing a ground rod you must also refer to the ground rod rules which state you need less than 25 ohms so we usually drive 2 six or more apart and call it a day
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In my 2023 codebook under 250.53(D)(2) you are correct that when a metal underground water pipe is used as an electrode it must be supplemented by an additional electrode. I suppose if your supplementing 'something' that something would be a 'primary thing' so I can see how you would think that way.
If a metal underground water pipe is present it must be used either way and one cannot be used alone.
Now you could chose any of the electrodes permitted under 250.52, if you for example choose to supplement with a ground ring or concrete encased electrode (UFER) you are done. If you had two copper underground water pipes for any reason you could supplement one with the other.
Any time you choose to use rod and Pipe electrodes my understanding is per 250.53(A)(2) you need two rods or pipes. There is never a case where you can drive one under that section (other than the exception). Perhaps the only time you could use one is under 800.100 or 250.54.
 
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tortuga said:
In my 2023 codebook under 250.53(D)(2) you are correct that when a metal underground water pipe is used as an electrode it must be supplemented by an additional electrode. I suppose if your supplementing 'something' that something would be a 'primary thing' so I can see how you would think that way.
If a metal underground water pipe is present it must be used either way and one cannot be used alone.
Now you could chose any of the electrodes permitted under 250.52, if you for example choose to supplement with a ground ring or concrete encased electrode (UFER) you are done. If you had two copper underground water pipes for any reason you could supplement one with the other.
Any time you choose to use rod and Pipe electrodes my understanding is per 250.53(A)(2) you need two rods or pipes. There is never a case where you can drive one under that section (other than the exception). Perhaps the only time you could use one is under 800.100 or 250.54.
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Thankyou

If you cant prove 25 ohms then you drive 2 rods really dont matter at that point if you have a water pipe your using a ground rod that must meet 25 ohms

thanks again
jeff
 
FREEBALL said:
When installing a ground rod for the service I was told yesterday that as long as i have the water pipe grounded i only need 1 ground rod.
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You need a supplemental electrode for the water pipe electrode. A single rod unless tested and proven to be 25Ω or less is not an electrode. Two rods are considered an electrode even if they were tested to be above 25Ω. The two rods would not require testing so install two and walk away.
 
FWIW A copper water pipe is always a better ground compared to rods.
Not that it matters much in electrical distribution.
Here telcom stuff like cell towers had to have a outside testing company test grounding resistance as the 'Design Goal' is 5 Ohms.
One time the guy tested a 1" copper water pipe alone that was not bonded to the system and it alone was under 5 ohms.
If I remember right in the soils here it takes a gournd ring and 6 rods to get to 5 ohms around a tower.
 
infinity said:
You need a supplemental electrode for the water pipe electrode. A single rod unless tested and proven to be 25Ω or less is not an electrode. Two rods are considered an electrode even if they were tested to be above 25Ω. The two rods would not require testing so install two and walk away.
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thanks yea he didn,t look like he was sure on code but said he followed mike holt. I did not argue in front of customer but just goes to show how much difference there is in interpretation been doing this for some 30 years and seems he couldn't find problems with my install so decided to remark on what I didn't have to do, IDK customer is happy, its safe and installed code compliant just blows my mind when new inspectors try to introduce new interpretations of code

Thanks again everyone stay safe
 
FREEBALL said:
thanks yea he didn,t look like he was sure on code but said he followed mike holt. I did not argue in front of customer but just goes to show how much difference there is in interpretation been doing this for some 30 years and seems he couldn't find problems with my install so decided to remark on what I didn't have to do, IDK customer is happy, its safe and installed code compliant just blows my mind when new inspectors try to introduce new interpretations of code

Thanks again everyone stay safe
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This is one of those code sections that is completely black and white. So with installations like these there is nothing for anyone to interpret one way or another.
 
don_resqcapt19 said:
I don't think the metal underground water pipe has ever been a stand alone electrode, at least not in the past 50 years or so,
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You made me look. The requirement for a supplemental electrode in all circumstances appears in the 1978 NEC, but not the 1971 NEC. The 1975 NEC isn't viewable on the NFPA website. (Anyone have a copy? 😁) So 50 years is about right, but prior to that it was permitted as a stand alone electrode.

One can still find houses around here where the FPE panel hasn't been updated and the GEC goes to the nearest convenient point on a copper water pipe that's electrically continous to the underground water service. That would have been compliant when those panels were installed. (The 25 ohm rule did exist but would have easily passed with metal municipal water distribution networks.)
 
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