2 amps on water pipe grounding conductor

[newservice]

I have about 2-3 amps on my 100A single phase service grounding conductor to the underground water pipe at my house, as measured with my clamp on ammeter. Neutral current is another ~2 amps ..which does add up given the currents on the two lines. Normal? I was kind of ..shocked....at first cause I always thought the neutral, if its connected well, would take all of the current. But as a moderator points out in another thread, the pipe is in parallel with the system neutral so some current is normal. Oddly, there is nothing flowing at all on the grounding electrode conductor. I did notice last year that I got a spark when disconnecting the water pipe ground which prompted this experiment.
POCO came out and guy looked it over, scratched his head and said the line crew would come out reterminate the drop neutrals, that it def wasnt normal.. however that hasnt happened yet Current goes almost away when main disconnect turned off, still something like half an amp there and also on the neutral. Anyone going to the state fair?

 

[George Stolz]

If your metal water pipe is electrically continuous to the neighbor's water pipe and electric service, you are using your neighbor's neutral.

Where are you measuring? You've got two statements that seem to contradict each other.

 

[jumper]

I have about 2-3 amps on my 100A single phase service grounding conductor to the underground water pipe at my house, as measured with my clamp on ammeter. Neutral current is another ~2 amps ..which does add up given the currents on the two lines. Normal? I was kind of ..shocked....at first cause I always thought the neutral, if its connected well, would take all of the current. But as a moderator points out in another thread, the pipe is in parallel with the system neutral so some current is normal. Oddly, there is nothing flowing at all on the grounding electrode conductor. I did notice last year that I got a spark when disconnecting the water pipe ground which prompted this experiment.
POCO came out and guy looked it over, scratched his head and said the line crew would come out reterminate the drop neutrals, that it def wasnt normal.. however that hasnt happened yet Current goes almost away when main disconnect turned off, still something like half an amp there and also on the neutral. Anyone going to the state fair?

Is the water pipe an electrode?

 

[Dennis Alwon]

I have the same confusion as you two do.

 

[newservice]

If your metal water pipe is electrically continuous to the neighbor's water pipe and electric service, you are using your neighbor's neutral.

Where are you measuring? You've got two statements that seem to contradict each other.

Thanks for the input, George. It probably is continuous, houses very close together here. I dont understand your question about what you dont understand...lol...about what Im measuring..im measuring the a/c amps with a clamp on amp meter in all the affected conductors on a standard 100a service with underground water pipe grounded, supplemented with an 8' ground rod.

 

[George Stolz]

See jumper's quote of your post?

 

[newservice]

See jumper's quote of your post?

Ok I think I know what you mean, there are two grounding electrodes, one being the metal underground water pipe, the other the supplemented ground rod. The current to the ground rod is 0. The current to the water pipe varies with whatever the load is but it's about half of the neutral current. I like your explanation that Im using my neighbors neutral, as recently upgraded the house next door and new grounding conductors n clamps on the water meter.

 

[Dennis Alwon]

2-3 amps is more than I would expect to see and I would not expect to see current on the conductor to the ground rod. Now find out if it is one circuit that is causing the problem by turning them off one at a time while someone watches the amp meter.

 

[jumper]

The resistance of the rods will be way greater than the interconnected water pipes. That is why you are reading so low amps on the rods.

 

[newservice]

[Shouldnt the neutral resistance be even lower? I would think it should take all the current, but, as George points out, anyone with a bad neutral is potentially using yours and vice-versa..through the municipal water supply pipe.

 

[George Stolz]

If they're all interconnected as described, there may be no problem at all. It's prudent to check your own neutral connections at the service and have the utility check their end, but it's probably nothing.

 

[infinity]

I have about 2 amps on the water pipe/GEC where it enters the foundation. I would consider this to be normal since we have a city water piping system where all of the houses are tied together. The pipe is in parallel with the neutral and under normal condition would have some current flowing on it.

 

[don_resqcapt19]

The path though the earth via the ground rod will have a very high impedance as compared to the impedance of the path via the common metal underground water piping system. With low currents, currents under 200 amps where the effects of inductive reactant are not really a factor, I would not be surprised if the common metal under ground water pipe has an impedance very close to or even lower than the service grounded conductor. The current will divide on all of the paths in inverse proportion to the impedances of the paths. If the metal underground has a lower impedance than the grounded conductor, then it will carry more current than the grounded conductor.

 

[newservice]

If the metal underground has a lower impedance than the grounded conductor, then it will carry more current than the grounded conductor.

Couldnt agree more Don, but, in the end, isnt it carrying that current back to the system neutral?

 

[kwired]

Couldnt agree more Don, but, in the end, isnt it carrying that current back to the system neutral?

The current is trying to find a way back to the neutral terminal on the transformer where it originates. Since the metal water piping and electrical services on all the surrounding houses are all tied together it has many paths in which it could travel. Path of lowest impedance will carry most of the current but all paths will see some of it.

 

[Rick Christopherson]

The 1/2 amp you have on the ground when the main breaker is off is due to a super node situation with the neighbors sharing parallel paths on the ground and neutral. Some of your neighbor's neutral current is flowing through your bonding location.

When the breaker is live, it is not uncommon to have significant current flowing on any ground path. A buried water line makes an excellent electrode due to the length of the pipe that is in contact with the earth. It will have a very low resistance. There will be a parallel path back to the utility.

 

[newservice]

Looks to me like George nailed it; Im using my neighbors neutral. Ive been doing this for several years now and that thought never occurred to me. Could be a combination of neighbors neutrals but..Just for kicks, I went to the house next door this morning with the owners (i own it) permission. That house is vacant with power off (plastic clips at the meters). I recently upgraded the services there and the system is connected to the poco. Checking the water pipe current at house #2, it matched house #1. So then, with a lead light plugged into house #1 via extension cord, I disconnected the water pipe connection at house #2. It sparked slightly and my lead light dimmed. Will be having the poco terminate those neutral connections at the street and at service point for house #1. Thanks for all the answers, many of you had great relavanat points also.

 

[infinity]

Looks to me like George nailed it; Im using my neighbors neutral. Ive been doing this for several years now and that thought never occurred to me. Could be a combination of neighbors neutrals but..Just for kicks, I went to the house next door this morning with the owners (i own it) permission. That house is vacant with power off (plastic clips at the meters). I recently upgraded the services there and the system is connected to the poco. Checking the water pipe current at house #2, it matched house #1. So then, with a lead light plugged into house #1 via extension cord, I disconnected the water pipe connection at house #2. It sparked slightly and my lead light dimmed. Will be having the poco terminate those neutral connections at the street and at service point for house #1. Thanks for all the answers, many of you had great relavanat points also.

So with 2 amps of current on the water pipe you're assuming that your service neutral is open somewhere?

 

[newservice]

I think I just proved it in my previous post.

 

[kwired]

I think I just proved it in my previous post.

With your description I say you only started to prove that. Did you go back to first house and measure voltages? Measure with somewhat significant imbalance so the neutral will be loaded well. What is a lead light? By disconnecting the water pipe on house #2 you did change the resistance of the path of the neutral back to the transformer so depending on the load and resistance some change in output of a light could be expected.