Current Measured on water and gas lines

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Handy hank

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Round Hill, VA
I have a nagging problem about measuring electric current on metal water and gas line coming into my daughter's home. At the outset, 4-6 Amps were read on the water line. It fluctuates depending on what loads are on in the home. A toaster oven drawing 15 Amps causes an increase of 3 Amps on the water line. 2 electricians have come to inspect and not found any wiring problems in grounding system, and the power company came to measure the net current on the main service line who found 1.2 Amps flowing despite the Main CB being OFF. With main CB on, about 2 Amps was measured. The power company says there's no problem in the house, and the electricians can't find anything wrong. Discussions ensue that involves there maybe being a problem at a neighboring home.

Does the "residual" (or possibly "objectionable" per NEC 250) current flowing despite the Main CB being OFF constitute a problem in the home OR a problem in a neighboring home cross feeding into my daughter's home?
What amount of current measured on the water line or gas line is acceptable?
Does this residual current flowing register on the watt-hour meter despite the Main CB being OFF?
 
It is quite possible that the current is coming through the earth from a neighbor who is on the same utility transformer. If so short of getting the utility to put your daughter on a transformer by herself, there is probably very little that can be done.

Whether it is objectionable or not depends on your POV.
 
petersonra said:
It is quite possible that the current is coming through the earth from a neighbor who is on the same utility transformer. If so short of getting the utility to put your daughter on a transformer by herself, there is probably very little that can be done.

Whether it is objectionable or not depends on your POV.
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If a neighbor on the same transformer has a neutral problem, say a loose connection or even an open, we'd see the grounding taking up their neutral current and feeding through water and gas lines to my daughter's home neutral.
Is there a rule of thumb about what is acceptable current readings on water and gas lines? "Some" might be expected.
 
As mentioned, the "problem" may even been from connections outside your daughter's home (neighbor on same transformer, POCO, etc).
That said, you should not be measuring and current flow on the gas line. Her line should be electrically isolated from the neighborhood distribution system. If you are showing curent flow on the gas line I would contact the gas co. and have them check the isolation fitting (normally at the gas meter)
 
augie47 said:
As mentioned, the "problem" may even been from connections outside your daughter's home (neighbor on same transformer, POCO, etc).
That said, you should not be measuring and current flow on the gas line. Her line should be electrically isolated from the neighborhood distribution system. If you are showing curent flow on the gas line I would contact the gas co. and have them check the isolation fitting (normally at the gas meter)
Click to expand...

good point. the UG gas line should be galvanically isolated at the meter.
 
Handy hank said:
I have a nagging problem about measuring electric current on metal water and gas line coming into my daughter's home. At the outset, 4-6 Amps were read on the water line. It fluctuates depending on what loads are on in the home. A toaster oven drawing 15 Amps causes an increase of 3 Amps on the water line. 2 electricians have come to inspect and not found any wiring problems in grounding system, and the power company came to measure the net current on the main service line who found 1.2 Amps flowing despite the Main CB being OFF. With main CB on, about 2 Amps was measured. The power company says there's no problem in the house, and the electricians can't find anything wrong. Discussions ensue that involves there maybe being a problem at a neighboring home.

Does the "residual" (or possibly "objectionable" per NEC 250) current flowing despite the Main CB being OFF constitute a problem in the home OR a problem in a neighboring home cross feeding into my daughter's home?
What amount of current measured on the water line or gas line is acceptable?
Does this residual current flowing register on the watt-hour meter despite the Main CB being OFF?
Click to expand...
That is a very strong indication that there is a problem with the grounded conductor between the utility transformer and the main bonding jumper for your service.
 
don_resqcapt19 said:
That is a very strong indication that there is a problem with the grounded conductor between the utility transformer and the main bonding jumper for your service.
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I find the older I get, the dew brain cells are firing, but would that be the case since he's showing current with the main "Off".
I would tend to think the problem might be more outside of his area with the urrent flowing back thru the pipe his neutral to the transformer.
 
augie47 said:
I find the older I get, the dew brain cells are firing, but would that be the case since he's showing current with the main "Off".
I would tend to think the problem might be more outside of his area with the urrent flowing back thru the pipe his neutral to the transformer.
Click to expand...

I agree with this line of thinking. But since he had 1.5A with the main off and 2A with the main turned on, this may indeed be a multiple location problem.
 
augie47 said:
I find the older I get, the dew brain cells are firing, but would that be the case since he's showing current with the main "Off".
I would tend to think the problem might be more outside of his area with the current flowing back thru the pipe his neutral to the transformer.
Click to expand...
There may be more than one issue, but with a 3 amp increase when a load in the building it turned on, there is no question in my mind that there is a problem with the service neutral that serves that building. It would be highly unlikely that the current increase on the water pipe, as a result an issue at a different building, would occur at the same time he added load in his building.
 
don_resqcapt19 said:
There may be more than one issue, but with a 3 amp increase when a load in the building it turned on, there is no question in my mind that there is a problem with the service neutral that serves that building. It would be highly unlikely that the current increase on the water pipe, as a result an issue at a different building, would occur at the same time he added load in his building.
Click to expand...
:thumbsup:
 
There may well be a neutral issue feeding more than one house, making it between the utility transformer and the distribution points.
 
If you have continuous metal piping connecting to all houses in the neighborhood and all of them are bonded to the electrical service grounded conductor - you have a huge network of parallel paths. Even if there are multiple transformers in the neighborhood, they are all bonded together via a MGN. There is somewhat unlimited number of paths for current to flow.

When you have parallel paths current takes all those paths. The lowest resistance path carries the majority of the current but all paths do carry some current. This is why even when OP has the main breaker open, there is still some current on the water line, it is current from that network and the portion of it that happens to be flowing in that path. As long as that network remains intact there is nothing you can do to prevent those currents from straying throughout the network. The biggest danger here is for the plumber that opens the path when working on the piping.

Since 1996 NEC we have been required to run GEC to the first five feet of piping after it enters the structure. This does help limit that current path to only the first five feet of piping into the structure, and the risk to the plumber typically only involves first five feet of pipe or if they would be opening something outside the house in the main supply.

If this is an older application that has the GEC landed somewhere besides within first five feet of entry - you can move the GEC to within first five feet and that will at least remove current from other piping through the house, presuming there is no second pipe leaving the house that makes up an additional path in the neighborhood network, metallic water line to an outbuilding that also has electricity on same property would be an example that might still leave you with troubles.
 
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