When I removed the valve at my meter I had to take the groung wire off the copper pipe. When reinstalling the valve I noticed a small spark of electricity when I touched the valve to both sides of the gap in the pipe so I took a reading: It was about 1 volt AC. The resistance across the gap was 0 ohms (just as if there was no gap). Are these normal readings?

No. you have a leakage to ground and that indicates an electrical fault somewhere. Have it checked. I once removed a water heater and the spark across the union when I separated it was more of an arc. I told the customer that she should have the electical system checked for problems. She asked if that was why everything had just burned out and the big console TV was smoking? I threw the TV into the front yard, and then checked for any other potential fire hazard and then called my city electrical inspector friend to see what had happened. Her utility neutral had failed and the system was grounded to the hot water piping. When I broke the union it destroyed the 115 volt phase and everything in the house was fed 240 volts, which burned out almost every appliance and light bulb that was on at the time. A few survived because they were balanced loads.

In addition, I have been walking through a house with my current detector turned on and had it go "ballistic" when I went by an appliance. Usually the only reason no one has gotten a shock from such an appliance is because there is no close ground point. This is less of a problem now that the cords have the ground wire in them but if a 3 to 2 adapter is used it can still happen. I once found that a friends entire trailer shell was "hot".

Danni, people have also been killed, when disconnecting a meter that didn't have a jumper wire installed around it.

An ohm reading taken between two points where a voltage difference exists is not going to be valid, and in many cases will damage the meter. In resistance mode, the meter uses current from its internal battery to make the test. The external source will either add to or subtract from that current, giving you at best a wrong answer, and at worst, smoke from the meter.

Finding a difference of one volt between the plumbing and the rest of the electrical system ground isn't necessarily so bad. Your electrical system ground and neutral are tied together at your service entrance, and so are those of all your neighbors on the same transformer at their service entrances. There are driven ground rods at all those points, and the utility also has a ground rod tied to the center tap at the pole. Because loads within a house aren't going to be perfectly balanced, each of those ground rods is getting pulled off center by a small amount. That results in small voltage gradients throughout the dirt all over the place, and your water pipe just happens to be stuck in a place that's a volt away from where your ground rod and service entrance neutral are.

That being said, even though it's likely that there's nothing wrong, why not take a look at your ground rod and make sure that everything's properly bonded.


-- J.S.

What happened to you is the reason why code now requires the plumbing to be bonded to the electrical system ground within 5 ft. of where it enters the building, and nowhere else. To have all the neutral current running through the water heater is just amazingly bad and dangerous, and yet stuff like that does happen. I know of one plumber who won't open anything up without first jumpering around it with car jumper cables. He got a real bad shock once from somebody using the plumbing to bootleg a neutral.

The really irritating thing is that this was no accident. Somebody had to deliberately install this stuff in such a wierd way that the neutral ran through the water heater.

What actually happens in a loss of neutral accident is that the leg with the lighter load sees more than half the 240 volts, and the heavier leg sees the rest. So stuff starts blowing out on the light side, progressively increasing the imbalance until the last item is destroyed. At that point, the last circuit is broken and everything goes off. As Murphy would have it, expensive electronics items usually draw a lot less power than cheap stuff like heaters, irons, toasters, and light bulbs.


-- J.S.

John it seems you know something about elec. so I would like for you to answer this question. It is no longer required to ground to the cold water on residential const in my area yet is still very much required on commercial const.So here is the question. If it is for grounding purposes what good is a copper waterline buried less than 2 feet and probably transitioning to pvc within 5 feet of the building.Is it the water in the line because pvc pipe itself has no conductive properties. from a plumbers standpoint it only creates more jobs like repipes in the event of lightining strike or severe surge.Or so it seems.

La, under the National Electric Code, if there is at least 10' of buried metallic water pipe coming into the structure, it shall be used as a part of the "electrode grounding system". If the incoming water pipe is plastic or there is less than 10' of metallic pipe in contact with earth, the water pipe is not part of the "electrode grounding system". Any interior metallic water piping within the structure shall be "bonded" to the electrical service enclosure, the grounding electrode conductor or the grounding electrode. Grounding or bonding the metallic water pipe to the electrical service, will help clear a fault (trip a circuit breaker/blow a fuse) in the event that an electrical current is imposed on it. The "grounding electrode system" is in place to help dissipate excessively high voltages (lightning) that might appear in the system. A buried metallic water pipe is not to be used as the sole grounding electrode by newer NEC codes. It needs to have a supplemental electrode bonded to it. Just like plumbing codes, different areas use differnt codes and/or modify existing ones. I don't know why residential water pipe grounding/bonding would be eliminated, while keeping the commercial requirement.



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In this area, the electrical box has to have a lable specifying that there is a non-metalic water supply and the electrical service has to be grounded with one or two ground rods.

Is this a stand alone current detector like a geiger counter? How does it work? I've only seen one that is shaped like a circle that that you open up and put around a wire to see how much current it's drawing.

No, it is an induction tester that you hold near a wire, or device, to see it it has power in it. One is called a TicTracer, but there are many other versions. One of the differences is in how low of a voltage it can detect. Some only work on lines which are 100 volts and higher, while others will go down to the 24 volts of irrigation system control wiring. The one I was using at the time had an on/off switch, rather than an "on demand" push button. Therefore it was on when I entered the trailer, and passed by the "hot" appliances. I also discovered a commercial refrigerator which had been wired backwards to the outlet and the hot wire was feeding into the ground and from there to the exterior. That one had just been installed so no one had been endangered, yet.

Here in Los Angeles we don't get all that much lightning, so it could be that your local AHJ is thinking the same thing you are. But it would only be a good idea if the interior plumbing is non-metallic, like PEX. I strongly believe that metal plumbing, and every other piece of metal that's fixed to the building and of substantial size should be bonded to the electrical system ground. That way if a hot wire ever accidentally comes in contact with it, the breaker will trip and the failure condition will be safe. I'm putting on a copper roof, and I'm going to ground it just in case some future owner nicks a hot wire on some Christmas lights or some such thing. But in a high-lightning environment like you have, that might not be such a good idea.

A piece of copper pipe that goes 2' down and 5' over could be a pretty good ground, but that would depend on the soil conditions -- moisture and chemistry. The PVC pipe is an excellent insulator, and the water in it is only a fair conductor, so that part of things is useless as a ground.


-- J.S.

Thanks for the info. Ive often wondered about this but never been given a straight answer.

John Sprung are you related to the Sprungs from Cochise County Arizona?
Brian

Someone already mentioned it but I will reinforce - permanently install a jumper wire (#6 copper stranded) from the supply side to several feet past the meter. this should never be removed. You could easily have been killed, as you would have been the conductor connecting the ground fault to ground.

Not that I know of -- There are also some probably unrelated Sprungs in Canada, in the temporary buildings business.


-- J.S.

I have a question somewhat related to this topic.
I suspect that the water pipe to which my electrical panel is grounded may be carrying current.
I am not a plumber or electrician but would be very grateful for any advice you can give me.
How can I measure whether the water pipe is in fact carrying current?
Is it normal for a water pipe used as a ground to carry current, or does that only happen with an electrical problem?
I live in a mid-townhouse and the water supply enters the house via one neighbour's basement, and exits via my other neighbour's basement. In this situation, does it matter at which point the ground is connected to the water pipe? In other words, can the ground clamp be moved from one end of the water pipe (next to neighbour A's wall, approx 4 feet from the electrical panel) to the other end of the water pipe (next to neighbour B's wall, approx 15 feet from the electrical panel)?

Good information. Inspectors tend to be picky about the distance between the main electrical panel grounding wire to both the grounding rod and a copper pipe (maximum distance 10' and 5' respectively).

One home we worked on was on piers over water. The main water line was CPVC underground from the water meter with a shark fitting to exposed copper line to the structure. Obviously no ground path here but the water pipe connection was still required. So, the grounding rod served 2 purposes (bonding and grounding)



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I have a friend his plumbing is grounded or bonded to the ground of the electric panel at the foundation ground. The foundation ground is approx. 10 ft. from the electric panel. He says when they connected the pipes to the electric panel he immediately started getting green stains in his sinks. It is a private well for a residential home so it is not connected to any other homes. It sounds like some sort of current or electrolysis? He has two PEX type fitting that look eaten up or ragged inside? Most of the house is copper. Does anyone have an idea of what is happening or how you would find the cause?