Objectionable Current - Water main

[hbiss]

Two questions:
1. How do you make the water main safe so pedestrians do not get shocked?
2. When the utility works go to work on water mains, how do they not get zapped when there is often objectional current on the water main?

There is no way you are going to figure this out without extensive digging and disconnecting the pipe. It may very well be that non-metallic sections were installed someplace along the line allowing the above ground section to be energized from the other direction. Have you measured the actual voltage on the pipe to a ground rod driven some distance away? And on the pipe to the utility neutral? That should give an idea of what might be going on. How about placing a load on it to the utility neutral to see how much current it can supply. It's one thing for people to say they feel a shock, quite another for there to be full line voltage on it.

-Hal

 

[don_resqcapt19]

So my first hunch of bonding both ends, part that emerges from ground, and part the dives back into the ground, was more or less in the right direction?

That would not do anything to get rid of the issue.

 

[W@ttson]

That would not do anything to get rid of the issue.

Would it not be similar to what a plumber does of jumpering over a meter to replace it? I assume that there is some sort of discontinuity and there for a potential difference. By jumpering over the exposed section would cause it to be at the same potential.

 

[W@ttson]

There is no way you are going to figure this out without extensive digging and disconnecting the pipe. It may very well be that non-metallic sections were installed someplace along the line allowing the above ground section to be energized from the other direction. Have you measured the actual voltage on the pipe to a ground rod driven some distance away? And on the pipe to the utility neutral? That should give an idea of what might be going on. How about placing a load on it to the utility neutral to see how much current it can supply. It's one thing for people to say they feel a shock, quite another for there to be full line voltage on it.

-Hal

I have not had the chance to go out to the site yet. All I know is of the complaints and that the section of watermain has been cordoned off with a fence.

 

[electrofelon]

If the water people see this as a real problem, they can fix it in their codes. Simply require a short length of nonmetallic pipe between the water main and the building.
However, this issue is rapidly going away, as there is not a lot of metallic water mains being installed any more...none in my area. All replacements and new mains are non-metallic.

I do hope it goes away eventually. if I can rant a little bit, this issue actually drives me crazy. The NEC is so obsessed with grounding, that it throws many of its other tenets - parallel paths, getting neutral current off non current carrying metal parts - right out the window and makes for a bare conductor and piping system carrying neutral current continuously. They should have required a dielectric union where a metallic pipe system leaves the structure.

 

[mtnelect]

I do hope it goes away eventually. if I can rant a little bit, this issue actually drives me crazy. The NEC is so obsessed with grounding, that it throws many of its other tenets - parallel paths, getting neutral current off non current carrying metal parts - right out the window and makes for a bare conductor and piping system carrying neutral current continuously. They should have required a dielectric union where a metallic pipe system leaves the structure.

I have a "Insulate Union" on my water service, but it's only for 3/4", but 14" is a little much ! So, I think you are referring to the smaller services, yes ?

 

[hbiss]

Would it not be similar to what a plumber does of jumpering over a meter to replace it? I assume that there is some sort of discontinuity and there for a potential difference. By jumpering over the exposed section would cause it to be at the same potential.

The problem is the potential on the pipe and the earth the people are standing on or vice versa. (Assuming that's how they get shocked.) It's not going to be as simple as a discontinuity someplace.

Do some tests and get back to us.

-Hal

 

[winnie]

Would it not be similar to what a plumber does of jumpering over a meter to replace it? I assume that there is some sort of discontinuity and there for a potential difference. By jumpering over the exposed section would cause it to be at the same potential.

If the problem is caused be current flowing along the pipe, and if there is a break in the pipe (say some sort of dielectric union is already present), then bonding around that break will remove the hazard. But you have not yet determined that this specific scenario is causing the problem.

My hunch is that there is current flowing in the soil from some source, and the pipes are creating concentrated regions of step potential. You will need to locate and correct the source of this soil current, or you will need to do major work to alter the shape of the step potential field. But that is a hunch, not a definite answer.

I'm with Hal. You need to measure what is happening before you try to fix anything.

Jonathan

 

[kwired]

I have a "Insulate Union" on my water service, but it's only for 3/4", but 14" is a little much ! So, I think you are referring to the smaller services, yes ?

If there is any voltage rise on your grounded service conductor (which there is at least some any time it is carrying current) that voltage will be measured across your isolating fitting. If it is high enough voltage you will feel it if you contact both sides

 

[mtnelect]

If there is any voltage rise on your grounded service conductor (which there is at least some any time it is carrying current) that voltage will be measured across your isolating fitting. If it is high enough voltage you will feel it if you contact both sides

I would call it "Abe Normal" ever sinch the utilities decided to have a grounded connection between the primary & secondary.

 

[electrofelon]

I would call it "Abe Normal" ever sinch the utilities decided to have a grounded connection between the primary & secondary.

Note that even in the absence of a multi-grounded neutral distribution system you would still have current flowing on water piping systems between buildings. The only way to eliminate that (besides going to an ungrounded premise system) would be to have a dedicated transformer for each structure served which would greatly increase costs (looking around my town, utility typically feeds 6 to 12 houses off of one transformer).

 

[mtnelect]

This might help to explain my position on multi-grounded neutral distribution systems.

 

[don_resqcapt19]

Would it not be similar to what a plumber does of jumpering over a meter to replace it? I assume that there is some sort of discontinuity and there for a potential difference. By jumpering over the exposed section would cause it to be at the same potential.

The description in this thread does not sound like an high impedance or open pipe connection. That is the only type of condition that the proposed bonding would help with.
The only real answer is a complete investigation as to the source of the voltage and current. Without that, everything else is just a guess.

 

[don_resqcapt19]

I do hope it goes away eventually. if I can rant a little bit, this issue actually drives me crazy. The NEC is so obsessed with grounding, that it throws many of its other tenets - parallel paths, getting neutral current off non current carrying metal parts - right out the window and makes for a bare conductor and piping system carrying neutral current continuously. They should have required a dielectric union where a metallic pipe system leaves the structure.

That would be outside the scope of the NEC. If that is to be done, it would have to be in the plumbing codes.

 

[electrofelon]

That would be outside the scope of the NEC. If that is to be done, it would have to be in the plumbing codes.

I don't see why, they can do whatever they want. Isn't an ufer for the concrete/foundation people? Or what about a parallel path on a sds? Doesn't matter if the parallel path is on a different trades equipment. Not to mention their meddling in product standards.

 

[don_resqcapt19]

I don't see why, they can do whatever they want. Isn't an ufer for the concrete/foundation people? Or what about a parallel path on a sds? Doesn't matter if the parallel path is on a different trades equipment. Not to mention their meddling in product standards.

The NEC does not require the installation of a concrete encased electrode. It only requires that you use it as a grounding electrode if it has been installed.

Not sure what you mean about product standards...it works both ways...sometimes a change in a product standard triggers a change in the NEC and sometimes a change in the NEC triggers a change in a product standard.

 

[electrofelon]

The NEC does not require the installation of a concrete encased electrode. It only requires that you use it as a grounding electrode if it has been installed.

Not sure what you mean about product standards...it works both ways...sometimes a change in a product standard triggers a change in the NEC and sometimes a change in the NEC triggers a change in a product standard.

Right but in practice 99.9% of buildings will have rebar, so either the concrete people will end up doing electrical work or the electrician will end up doing concrete work.

Anyway, I don't see a statement about prohibiting neutral current flowing on piping systems to be in conflict with anything in 90.2 if they wanted to, which they don't because the organization is too far gone and a lost cause.

 

[mtnelect]

Right but in practice 99.9% of buildings will have rebar, so either the concrete people will end up doing electrical work or the electrician will end up doing concrete work.

Anyway, I don't see a statement about prohibiting neutral current flowing on piping systems to be in conflict with anything in 90.2 if they wanted to, which they don't because the organization is too far gone and a lost cause.

I would include the utilities in that statement.

 

[kwired]

The NEC does not require the installation of a concrete encased electrode. It only requires that you use it as a grounding electrode if it has been installed.

Not sure what you mean about product standards...it works both ways...sometimes a change in a product standard triggers a change in the NEC and sometimes a change in the NEC triggers a change in a product standard.

It also requires to use 10 feet or more of underground water piping as an electrode. So if the plumber were to put an isolating fitting between interior and exterior piping NEC would still require us to bond to both.

 

[kwired]

This might help to explain my position on multi-grounded neutral distribution systems.

Is double edge sword.

Not using grounded conductors for current carrying purposes would probably be the way to do it, both for facilities use as well as distribution. Then multi-ground just about everything possible but it won't be on any conductors that carry current in normal operation.