ECN Forum Forums General Topics of the Trade General Discussion Area Amps on the water line

Consider a very basic, ONE service from ONE transformer installation where the underground metal water pipe is in close proximity to the utility ground on the transformer (this is not uncommon). Consider the resistance through earth as relatively low across the gap between the transformer ground and the pipe. The neutral is bonded to the grounding electrode at the transformer AND at the service. Therefore the electrical circuit through neutral conductor and the electrical circuit through the grounding electrode conductors, the pipe and earth (together) are in PARALLEL. The neutral current WILL divide between the two. The amount on each depends on the impedance of each. BASIC ELECTRICITY. In the case I describe above, with a reasonable neutral current, 4 amps could easily be expected!! Add in multiple currents from different services and utility connections (maybe a miswire too)and the picture become more complicated....but still obeys the same rule!

Something I didn't think to ask earlier....where and how was this amperage measured? At the H2O meter with a clamp-on ammeter? Up near the entrance of the plumping system into the house?

Just curious,
Doc

Joe,
How do we protect the plumber replacing the underground water pipe outside of the building? Why does the electrical code require us to place other tradesmen in serious danger?
Don

Virgil is 100% correct again.

I really like the call to Paul and me - that's cool!!! Thanks for the compliments!!!

I find anywhere from 1 Amp to 25 Amps flowing on water lines - all depends on the location.

It kinda' sucks, but it does kind of offer relief, as this would be common on a code compliant install [once again, depends on the location and where the reading was taken!]

Scott S.E.T.

around here the ahj and the utility won't let you bond around the water meter!

Scott,
Can you expand on any other methods of reducing the current besides what virgil has mentioned above. Let me start by posing the following:
I think that we can all agree that article 250 doesn't stop you from driving supplementary ground rods if desired. If (and that is a big "if") a person thought that current on the main trunk line entering their house was going to pose a problem. Where would you suggest driving the additional rods? Would you say, open up the ditch where the trunk is buried, and drive rods every 10', and bond to the pluming line? Just at the meter? Also, I can see that the condition of the soil is going to play a role. Dry soil is more resistive, wet soil is going to be the opposite. Enlighten me, if you would.

Putting on my shades,
Doc

Doc,
I can't imagine any type of made electrode system, including ufers, to have a low enough resistance to make much of a difference in the water pipe current where there is a common undergound water piping system. We are really talking about a direct metal connection that is in parallel with the grounded conductor. This is also a source of EMF and as we learn more about the dangers of EMF, I would expect that the code will require that the under ground water piping system be electrically isolated from the interior water piping system. In many areas, all new underground water distribution systems are nonmetallic and the problem will go away. Even where the water service is metallic from the main to the house, there will be little current flowing if the water main is nonmetallic.
Don

I second Don's comment. With multiple paths back to the xfmr neutral there will always be some current on the water lines, but certainly a plastic coupling or the use of a plastic water line and/or main will reduce it to a negligible value.

There's still the old problem of what happens when a neutral goes high-res./open of course.

Don:

How do you propose to change the code so that they will not be subject to injury?

Please give the references in the code that will have to be changed and how, so we can discuss them here before the proposal closing date in November 2002.

Joe,
I'm not sure that it can be accomplished in the NEC. The only effective change that I can think of would be to require that the metal underground water pipe have a section of nonmetallic pipe at the point of entrance to the building. I think that this would have to be in the plumbing codes. The biggest problem is when the service neutral is open, and a plumber is repairing the outside under ground water pipe. I don't see any way for a plumber to test for the problem before cutting or taking apart the pipe. An amp probe will show the current, but if it is only current caused by a parallel path, there will not be a hazardous voltage between the two sections of the pipe after they are taken apart or cut. If however there is an open neutral, the same current flow on the pipe will result in line or near line voltage between the two pipe sections. This places the plumber in danger.
I think that a first step, could be made by putting a second exception in 250.50(A)(1).
"Exception #2: Where an insulating section is installed on the metal under ground water pipe at the pipe's entrance to the building, it shall not be required to use the metal underground water pipe as a grounding electrode.
FPN: See 250.104(A) for the required bonding of the interior metal water piping system"
Don