I recieved a call from a potential seller of a single family home saying the buyer's inspector measured 4 amps on the water service. Our village does not do single family home sale inspections. The problem could be a loose neutral anywhere on the block. Our plumbing code does not allow plastic water lines. Anyone have a solution for this?

Wow...

Allow me to add to your Q...

The way I understand it is that if every house has copper lines between them, and every service is bonded to the lines, then the parellel path cannot be avoided... In fact, good workmanship with strong continuity on the water lines will actually allow more current to flow... They will divide the current between them in inverse proportion to their resistances, so a good connection on the water lines is going hand in hand with the poor connection on the neutral, and a bad neutral isn't always the case either... What's the resistance of 3/4" Copper Pipe per 100 foot or so? How can one relate this resistance to divide the load?

(Psst: Pauluk or Scott35 listening here?)

I figure if ya got current on your grounding electrode conductors, it could be 'cause ya got a really good ground. So, is it a bad thing?

I'll 2nd Virgil's response
(don't U ever sleep?)
and add here....

'Other' Grounding Electrodes can be established, and a plastic coupling can be added to the H2O main to oppose parralleling.

The GEC can be left as is on the house side of the H2O main, as a 'bond'

I always thought I slept too much...

Here it's already 8:00 and I'm still drinking my coffee... Joe's probably at the site already and wondering where I am...

I'm like a train, hard to get started and hard to get stopped...

Good thing I'm self employed...

Look here for some information that may be of help:

http://www.awwarf.com/exsums/90702.htm

Let me tell you a little story that may, or may not shed some light on what could be the problem. A few years ago, an instructor told me of a "strange" situation, and how they solved it. The complaint was that the home owner and his family kept getting shocked by the plumbing system in the house. What really added to the problem was that it would "come and go". One day everything was fine. Then, for some strange reason, someone would get shocked on the kitchen sink, a shower head, etc. This instructor of mine went to investigate, and this is what he found. The plumbing system became hot only when the dishwasher was on. So, they pulled the dishwasher out, and had a look. Whoever installed the dishwasher did not connect the EGC. In fact, he said, that they had cut it off at the outer sheath of the NM cable. On top of that, they ran the NM cable under the frame of the dishwasher (between the floor and the frame). As a result, over time, the dishwasher rubbed a hole in the insulation. When the dishwasher went into the rinse cycle, it would shake alittle, and the frame would come to rest on the hot conductor. Now, here is the other twist. There was no bond between the plumbing system, and the neutral at the service. So, what was the result? No path back to the service for the ground fault. With copper lines connecting all the plumbing equipment, you've got a "hot" plumbing system.
Steve,
Sparky and WV66 know a lot more about residential applications than I do. So, I would consider what they have to say, and while you are out there on site take a look at all the equipment that is connected to the plumbing system, and check for a fault with no return path to the service. Also, check the bond between the plumbing system, and the neutral at the service. If it doesn't exist, bond it, and see if it helps. That bond could cause breaker(s) to trip. If it does, then you will know which equipment is the problem.
I have heard of people doing what Sparky is suggesting, but I've never had the "pleasure" of doing it myself. At least consider what I have to say, and if it works for you, then, more power to you. If it doesn't work........hey, I tried.

Smoke on the water line,
Fire in the sky,
Doc

Sparky, is correct. There will always be current on the metal under ground water piping system in a code compliant installation if the water piping system is common to other buildings connected to the same utility transformer. In some cases, this path via the water piping system may even be a better path than the service neutral. Also remember that the current you are measuring on the water pipe may very well originate in a different building. This current exists even when there are no problems with the service grounded conductor. It will, of course, increase if there is a problem with the service neutral.

Yep, if all the water lines are metallic throughout and with multiple grounds at the xfmr and each house, there's bound to be some current flowing on the pipes. How much will depend upon the relative resistances.

We have a similar situation in the U.K. with our PME distrubution system, which is basically the same as the standard U.S. arrangement as far as grouding goes.

In fact the very presence of currents on the pipework with this system resulted in our "code" ruling that a different grounding arrangement must be used in the supplies to gas stations and other similar plants.

Joe T.,

Nice Link!

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Thanks!

I was actually right for a change?!?!?

Here's another reason that recognizes the hazard.

250.68(B) Effective Grounding Path. The connection of a grounding electrode conductor or bonding jumper to a grounding electrode shall be made in a manner that will ensure a permanent and effective grounding path.

Where necessary to ensure the grounding path for a metal piping system used as a grounding electrode, effective bonding shall be provided around insulated joints and around any equipment likely to be disconnected for repairs or replacement.

Bonding conductors shall be of sufficient length [not like a banjo string] to permit removal of such equipment while retaining the integrity of the bond.

Reason: To protect the water service technician when they are removing the water meter, otherwise they are sure to get a shock!!

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

Don,

We're back on the "Single Point Grounding" subject again ( I think ) which I'm in favor of.

But, the problem with trying to combine a single point grounding system with the existing (nationwide) SERVICE system would be the same if a insulator was inserted in the incoming water line.

What happens when a person bridges that insulator, beit on a normally operating multiple premises service with, say 50% grounded conductor amperes is returning on the metal water line or on a system where a fault of some high value, say 10,000 amperes?

With-out a complete revamp of old services ( or in this thread, adding water line insulators on old systems as well).
I JUST DON'T SEE THAT EVER HAPPENING.

Glenn

Glenn,
The parallel path for the grounded conductor current creates excessive EMF. As we learn more about the health effects of EMF, I think we will see code rules designed to limit the EMF. I think that this will be the driving issue, and not the safety of the plumbers, but the result will be the same. Also code rules are not retroactive, so any change would only apply to new installations. There would be no requirement to make changes to existing installations.
In many areas the water pipe parallel path is disappearing. All of the water utilities in this area are using nonmetallic distribution mains. This prevents the direct parallel path back to the transformer. This may begin to cause the TV cable utilities problems, as their system also provides a parallel path for the grounded conductor current. Here again this parallel path for grounded conductor current is required by the NEC.
Don

[This message has been edited by resqcapt19 (edited 07-16-2002).]

Don,

Your point about the health effects of EMF driving changes in GEC practice, IMHO, is excellent. It is only a matter of time until the wave of litigation starts moving towards the crest (litigation for compensation for documented health effects).

Your comment about the cable company adds a whole new meaning to the ideas in "open neutral." A residential coax cable feed shield, depending upon how complete it is, will have a conductor gauge equivalent between #16 and #12!

Steve T,

Consider this image of a residential configuration. Three houses on three seperate adjacent lots, one power transformer and a common metal water pipe system.



It doesn't matter much what is going on in houses #1 & #2, one could shut off the service disconnect and remove the meter from the socket and there is still going to be neutral current.

This current flows when the house farther away from the transformer is unbalanced. The more the unbalance in #3, the more the current in #1 & #2.

This is from an ECN thread from last November titled New Service or Subfeed . This is not the only source of the current that might be found on the water service of your potential(?) client. The power company's distribution grid, depending on its configuration, may also cause measurable currents.

Al

[This message has been edited by ElectricAL (edited 07-17-2002).]

Joe and Don
I have seen suggestions to insulating the water lines before, leaving the 10 foot section intact and at that point inserting and insulating coupling to isolate the waterline from the rest of the system.
Also another problem with these waterlines is what has come to be known as a "Shorted Neutral" to the water line. This has to do with magnetic fields but it does happen and the return current winds up on the waterline.
These suggestions as I stated above, also stated that alot of plumbers carry jumper cables to jump the sevtion of pipe they are getting ready to cut. I havent seen this but suppose its possible.
My question is this, now that I have finally become aware of this, where does the current go execpt to another house and use its neutral to get back to the source. On one street I recently worked there were 16 houses on one transformer, I believe the transrormer was a 69kva type leaving about 25 amps per house and the tri-plex went everywhere I measured about 400 feet of triplex and during one of the hottest days the voltage drop was significant, since all these homes had some sort of A/C. The waterline current in the particular home I was working in was almost 10 amps. It seems to me that the utilitys have got to do a better job monitoring there systems and their terminations.
-Mark

Here's the information that is available at the reference link that I provided above:

Effects of Electrical Grounding on Pipe Integrity and Shock Hazard
Prepared by Steven J. Duranceau, Boyle Engineering Corporation and Melvin J. Schiff and Graham E.C. Bell, M.J. Schiff & Associates, Inc.

June 1996

AWWA Research Foundation Order Number: 90702

BACKGROUND
The practice of using water pipe as all or part of the grounding electrode system of buildings has been commonplace for more than 80 years. The practice was predicated on the assumptions that grounding of alternating current (AC) had little or no effect, compared to direct current (DC), on the corrosion behavior of buried metals; that current would only flow during off-normal conditions; and that there were no safety implications for water utility employees.

Some modern electronics (variable speed motors, televisions, computers, etc.) produce DC on the water service piping. Increases in corrosion rates due to stray DC are well documented. Further, when electrical transformers serve multiple buildings and customers, water services and distribution piping can act as parallel neutral return paths for AC from building electrical systems to the transformers. The alternating current can also increase the rate of corrosion of distribution and service piping. The increased corrosion leads to increased operating costs, as well as possible water quality issues for the water industry.

The presence of electrical currents on water services and mains results in random shock incidents for water utility employees and contractors during routine operations. The severity of these shock incidents ranges from mild tingling sensations to burns to numbness in the extremities. Most such incidents go unreported due to lack of a reporting protocol, poor record keeping, "macho" crew attitudes, and so forth.

This report presents the results of the study in terms of the shock hazard for utility employees and reduced service life of the mains due to possible external corrosion caused by current flow.

CONCLUSIONS

1. Shock incidents, minor and serious, occur frequently in the water utility industry.

2. Minor shock incidents occur at a much higher rate.

3. Shock incidents occur despite the efforts of utilities to provide their employees with equipment, training, and procedures for avoidance of shock hazards.

4. Electrical insulation of water services is effective in reducing the number of shock incidents.

5. Alternating currents cause corrosion and the rate of corrosion is much less than that of DC.

6. Electrical currents on water pipes change the corrosion state of buried metal piping.

7. Relatively high amounts (greater than 1 amp-AC) of alternating current were found on more than fifty percent of the water services tested during this investigation.

8. Electrically resistive, but not insulating, connections in metal piping systems are common and have an effect on grounding currents, which in turn affect pipe integrity.

9. Electrical insulators can affect water quality in terms of metal release.

RECOMMENDATIONS
1. The water utility industry should formally and directly approach the electric power distribution utility industry and the National Electric Code (NEC) committee of the National Fire Protection Association and declare their intent to electrically insulate exterior water services.

2. If a utility decides to install electrical insulation in an existing water service, the utility should coordinate with the power company and inform the building owner of the impending changes.

3. Water utilities should implement safety procedures consistent with state, local and federal requirements for protecting their employees from shock hazards inherent with water service piping which is bonded to the electric power system.

4. The NEC should be changed to require adequate grounding of a structure without considering the presence of underground water pipe.

5. Elevated lead and copper concentrations may be related to high levels of AC/DC current.

FUTURE RESEARCH

The decision to insulate water services is not simply a technical decision based on this or other reports. The question involves local, state, and federal agencies, including the U.S. Environmental Protection Agency and Occupational Safety and Health Administration, as well as consideration of indemnification and litigation risk. The legal and political implications are beyond the scope of this work and have not been addressed in depth by any previous study.

The water utility industry should conduct a study to determine the specific legal liability of electrical insulation of water services. The study should include potential litigation exposure from employees and customers, as well as from contractors and subcontractors who perform work for utilities and customers.

The brief tests of the effects of insulators on water quality which were found in this study for copper release should be extended to other pipe materials, lead in particular, and profiled for other water sources and treatment. Field verification and laboratory investigation of the effects should be pursued.

Touch read, radio, and remote meter reading systems rely on the measurement of a voltage signal to register water consumption and calculate the customer's bill. As far as can be determined, the possible effect of grounding currents and voltages on meter system accuracy has not been investigated.



[This message has been edited by Joe Tedesco (edited 07-17-2002).]

I figured this question would spark a lot of conversation about the subject, which I know has been talked about before. Trying to explain to people all the different variables involved is difficult when they are not electrically adept. Especially home inspectors who pick up bits and pieces of information and then misapply it in their jobs, or are just trying to avoid a lawsuit so make a mention of the situation just so they can say they put the info in their report.
I am going to print this thread and give it to them. I will let them know that these are just different peoples opinions and not necessarily fact so you good people don't get hit with a lawsuit. I, as a village inspector have tort immunity and can't be sued. but that's another subject.

Thanks all!!

Don,

We are on the same page on this issue as well as 99.99% of the time on most other issues.

I know the Code is not retroactive.

How many years will/would it take to have the parallel path(s) of the service grounded conductor eliminated with out some type of law. Never in my opinion.

Glenn