Current on water pipe

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George Linart

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Holland, Mi
I would like advice on the following issue we have in our neighborhood, specifically my home. I will describe the test we have done and the results, then ask for advice.
  1. We shut off the main breaker to my home
  2. We shut off the main breaker to my neighbors home across the street
  3. We placed a clamp meter no my neutral line
  4. We read 0.2 amps
  5. We then turned on my neighbors power
  6. Next we turned on two hair dryers creating 28 amps on his supply line
  7. His neutral line clamp meter read 23 amps
  8. My neutral line clamp meter read 5 amps
  9. This same test done in reverse created the exact same but opposite results
  10. This same test done with homes adjacent to my home did not add amps to my neutral line
  11. With this test, we create 5 amps running on the water pipe, therefore we are able to walk the water pipe using a Gauss meter
  12. The water pipes of our two homes must be connected to the main very close to each other

For one, I cannot understand how this is allowed to happen from a code stand point. More importantly, how do I correct this problem and stay within code. I see proposed solutions, but it seems to me I need to go through the proper channels to make sure I am in compliance with local codes. Do I talk to the power company, water company, and/or building inspector?

Additional, I wonder what the effect of this situation is if my home is supplied by a different transformer that my neighbors home?

Thank you
 
Forum rules do not permit us to assist a person who is not an electrician to perform their own electrical troubleshooting, repair, maintenance, or installation work. But I will (at least temporarily) allow this discussion to proceed. Please restrict yourself to questions that will help you understand what is happening, and why. We cannot help you with any corrective measures, other than to suggest that you contact an electrician.

Sadly, I have to run off to a meeting shortly, and don’t have time now to think through your description. If someone else can explain what is happening, then please do.
 
The first, and probably most important thing to recognize is that there would be little to no current measured on the ground electrode conductor if the utility ( we call them all POCO, for POwer COmpany) neutral wire from their transformer to both your houses was intact and working properly.
Since it is not, it appears that most of the neutral current is flowing through the house neutral to the main panel where it is connected to the Ground Electrode Conductor (GEC) and from there to the common water pipe ground and back through the earth to the earth connection of the transformer.
This would be an extremely dangerous condition and POCO service needs to be involved ASAP.
A sad fact is that even if it is their problem it make take several service calls before they send a tech who knows what he is doing and finds the problem.

Sent from my XT1585 using Tapatalk
 
GoldDigger said:
The first, and probably most important thing to recognize is that there would be little to no current measured on the ground electrode conductor if the utility ( we call them all POCO, for POwer COmpany) neutral wire from their transformer to both your houses was intact and working properly.
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I'm not sure why you say that. If I understand the OP's description correctly, when the OP has no loads running and the neighbor has 28 amps of 120V loads running, the neutral current is returning to the POCO transformer as 23 amps on the neighbor's neutral service conductor and 5 amps on the OP's neutral service conductor.

The neighbor's service neutral has a parallel path of neighbor's GEC to metallic water piping to OP's GEC to OP's neutral service conductor. Based on the current ratio, it appears this parallel path has a resistance 4.6 times that of the neighbor's neutral service conductor. Assuming the two houses' neutral service conductors are the same resistance, that would mean that the GEC--metallic water piping--GEC path has a resistance 3.6 times that of the neutral service conductor. If the metallic water piping system is all copper, that strikes me as a plausible value when everything is intact and working properly.

Cheers, Wayne
 
wwhitney said:
I'm not sure why you say that. If I understand the OP's description correctly, when the OP has no loads running and the neighbor has 28 amps of 120V loads running, the neutral current is returning to the POCO transformer as 23 amps on the neighbor's neutral service conductor and 5 amps on the OP's neutral service conductor.

The neighbor's service neutral has a parallel path of neighbor's GEC to metallic water piping to OP's GEC to OP's neutral service conductor. Based on the current ratio, it appears this parallel path has a resistance 4.6 times that of the neighbor's neutral service conductor. Assuming the two houses' neutral service conductors are the same resistance, that would mean that the GEC--metallic water piping--GEC path has a resistance 3.6 times that of the neutral service conductor. If the metallic water piping system is all copper, that strikes me as a plausible value when everything is intact and working properly.

Cheers, Wayne
Click to expand...
You are right. I misread where the return current measurements were made.
Your analysis is much more appropriate.

In answer to the OP's last question, the "foreign" return current would be lower if the two houses were on different transformers, but would still be present since the two transformer neutral taps will be connected by a POCO neutral wire.
 
George Linart said:
I cannot understand how this is allowed to happen from a code stand point. More importantly, how do I correct this problem and stay within code.
Click to expand...

There are two different "Codes" involved in your situation. The first, obvious code is the National Electrical Code (NEC). The NEC basically is regulating the wiring from your outlets to the splice between your electrical service supply conductors and the power company supply conductors.

The second code is the National Electrical Safety Code (NESC) which helps regulate the power company wiring, along with the rules that your local power company has for itself. The NESC covers the power company supply wires from the outside of your house, all the way back to the power plant.

For historical reasons, the power company uses the Earth and metal underground water piping systems as part of its "required" conductors. This goes all the way back to a money-saving engineering choice in the T. A. Edison power generating and distribution D.C. systems of the late 1800s. The later rapid acceptance and dominance of A.C. power systems left the so-called three-wire-Edison-circuit in place.

Here's the boiled down concept. On the house (load) side of the electrical service disconnect, the neutral current is carefully kept inside an isolated insulated conductive set of paths. On the transformer (line) side of the electrical service disconnect, the neutral current takes ALL available paths back to the transformer, the Earth, water pipes, wires. This is done BY CODE.

Strange. Eh?

A lot of good minds don't like it, but it IS code. The cost of changing it across the country is huge.

Depending upon the full set of wiring (all occupancies and systems) connected to your house's supply transformer, there may be a way to minimize the currents in the Earth and water pipes, but that should only be done by working with a competent local professional there in your neighborhood.
 
No additional explanation, but as a POCO guy, I just want you to be aware of the hazard if you get in series with the current paths. It could be fatal. The current you are seeing is some of the supply current returning to the POCO transformer neutral connections. If the service neutral can't carry all of the current, it will take all other available paths, including through you. One example is when we (also the water utility) had contractors install water meters in existing water service pipes. As they disconnected the water pipes, they were receiving sometimes painful shocks if they grabbed both pipe ends of an open section of pipe. The solution was to have them install a jumper across the piping joints until they had the meter installed and the pipes reconnected. Also, we found that there was voltage across the open piping even when the main breakers were turned off, likely due to POCO primary neutrals that were not sufficiently grounded or had high resistance connections. I guess what I'm saying is that current on water pipes is not unusual, so caution is required. If Code required bonding is correct, there will be no hazard and the electric bill will not be impacted at all.
 
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