in our basement we have a copper cold water pipe that runs to the outside faucet.

We have an electric water heater.

I felt tingling when standing barefoot on the concrete floor when touching the copper pipe. We have not noticed it elsewhere (but we have wooden floors and a fiberglass shower)

I have measured the voltage and it varies from 12V to 20V AC

I have turned all the circuits OFF in the house and the voltage is still present.

There are two copper stakes near the electric meter, one from before the meter was repositioned and a new one. I have not tried tying the two together to see if that removes the potential difference on the pipe...

A neighbor 2 houses down who has all PVC piping gets 9V between the water and ground.

Could the current be coming from outside our house through the water ?

I presume that shutting of the main breaker does not disconnect the neutral (I have not tried that yet). So if current was coming in via the neutral line we would still see the current in the pipe...?

 

Yes through the copper/iron pipe, although 20V is a pretty high potential to get through underground municipal plumbing. This could suggest that one of your neighbors has a loose or broken neutral wire in their electrical service. Do you know if your neighbors have experience any flickering, dimming or brightening lights?

A small amount of current through the plumbing can be considered normal, but not enough to feel a shock in my opinion. If you can get measurable voltage from the plumbing with your main breaker turned off, I recommend a call to the power company so that they can investigate the distribution system outside your home.

The breaker does not interrupt the neutral.

 

yes indeed ! On Saturday night the people next door reported lights blowing etc and they called the electric company who said they had a poor neutral connection ! I believe that has now been repaired but I am not at the house where the problem is to test it yet. I was hoping that could be the cause...!

The fact that you asked that very question gives me great confidence - many thanks !

Dale

 

You should have starrted your own thread. Hopefully the mods will catch it and move it for you.

anyway.

.did you turn off the main breaker?

possible but more likely the power company has a problem with a poor neutral connection.

Since this is at more than one house, I would call the power company and tell them. They will most likely send a service guy to check out their stuff.



Oh, and to the multiple ground rods. They might as well be tied together. Better more rods than fewer but there are rules to them being tied together properly.

 

I have moved the post above (Naps) because it is of the same topic.

 

At least you know you have a good cold water pipe ground! (Electrically conductive to the street and beyond.)

People replace underground metal pipe with plastic PVC, then no longer have a good ground. (And don't fix it.)

 

we still have the voltage on the pipes even though the neighbor's poor ground has been repaired.

I get the voltage (between 9 and 21 Vols AC) even with the main circuit breaker OFF.

I called the electric company (Central Maine power) and they sent someone out. He too is puzzled. He checked my ground in the breaker box. His meter also produced similar results.

He also tested a power socket in the basement and get this; his meter (and my meter) both show an 18 Volt potential with one probe in the hot slot and the other probe in the air (not touching anything - in the free air)! He and I are both very puzzled by that... how can the air have an 18Volt potential difference? We are in Maine with low temperatures - the air is thus dry and not moist.

He also checked the grounding of the transformer at the pole and it is grounded to the guy line for the pole. (This finding does not conflict with any readings - we seem to have a good ground - the issue is that current from the water pipe is finding it way to our ground/neutral). We both agreed that any voltage generated by water running through PVC pipes would be DC in nature and not AC which is what we are seeing.

The linesman suggested that because we are at the end of a road, we are also at the end of the power line and for some reason the 'neutral is not dissipating properly'. He mentioned that some dairy farms have a 'neutral blocker' installed to ensure that the water troughs have zero potential to ensure the cows drink from them.

He said he would pass on the information to his chief engineer....

 

Concrete is conductive

tap water, 1M to 100M ohm-meter
salt water 0.2 ohm-meter
fresh water, 1000 ohm-meter
concrete, 200 ohm-meter
human body, 5 ohm-meter
copper, 20 nanoohm-meter

and a slight tingling is about 1mA, so your [dry?] skin/body resistance is 10k to 20k.

Load down the voltage with a toaster; it has a resistance of about 12 ohms, so if the voltage drops in half, the source impedance is about 12 ohms.

Calculating this source impedance [the Thevenin equivalent impedance] may give a clue as to the source, and as to how much current will flow if you short these two points together.

Cattle are much more sensitive to current even though they are pretty large.
http://en.wikipedia.org/wiki/Stray_voltage

 

If you are getting the voltage from the city water pipe, try calling the city and have them temporarily remove the water meter. See if the voltage is coming from the street. Then tell the city it is their problem.

Also check with your local electrical inspector. See how much water pipe you need for a good ground or if you could install a ground rod or two (placed 6 ft. apart) for your main ground.

Then install a water pipe coupling with rubber compression fittings or a short length of PVC just after the water meter. This would electrically isolate your water pipes from the city water pipes.

BUT your electric system may presently depend on this connection for its ground, thus check first as to what would be a proper replacement.

AND warn anyone doing this plumbing work that there is live voltage present, and that touching both pipes at the same time could be a shock hazard.

 

thanks, I'll try and measure the impedance but I suspect that if is is a bad neutral elsewhere we may be seeing the combined impedance of multiple devices.

The 'town' in this case is an association who supplies the water and there are no water meters.

The house has two ground rods at present - and I think the house is well grounded - but perhaps tying the water pipes to that ground would help. I do not see any grounding of the water piping.

Would a small electrical gap in the pipe material not simply be bypassed by the water itself? i.e. if I installed 1 foot of PVC, the current would only have to travel through 1 foot of water to get back to metal pipe...

 

The rods should already be tied to the water line. Most commonly this is done on the neutral bar in the panel.

Water without impurities is a poor conductor of electricity.

 

OH! If you already have two ground rods, then that is an excellent grounding system.

Just install a electrically isolating section to your water pipe near the street, then connect a ground clamp to a cold water pipe and connect that to either your electric panel or to the ground rods as your local electrical inspector requires. (Run this by them first. They can be picky about grounding/bonding.)

Also it is a good idea to install a bonding jumper from the hot water pipe to the cold water pipe at the water heater. Water heaters have plastic which isolates the hot water pipes from the cold.

And ask your electrical inspector about bonding your natural gas pipe (if you have that) to ground as well.

As to the water bridging the gap, water does not conduct electricity! Pure water that is...
Google

 

I have not noticed if the pipes are grounded at all anywhere - perhaps this is the issue.... I need to search. The water and power service are on different sides of the building so perhaps the water has its own rod....

The fact that a neighbor gets a voltage with a probe in the running water suggests that there are enough impurities in our water to conduct electricity...

thanks for all the ideas and suggestions, keep them coming...

 

The water pipe would need to be "bonded" (grounded) to the same ground as the electrical system.

If need be, dig a trench around the house and run the ground wire around to the electric service.

The trick is to have all grounds connect to the same point, then everything is the same "potential". There is a thing called a "ground loop" which is caused by a difference in potential between two dissimilar grounds. Electronic things do not like "ground loops"!

BTW, the voltage present on the water pipe could be coming from a pump or other electrical equipment at the city/water district "water plant".

On ground loops...
Ground loop problems and how to get rid of them

 

yes I suspect this may be a summer job as the ground is frozen at present, or I run a big copper wire inside to the distribution panel. I am aware of ground loops and I was surprised to see two ground rods because of that. I mentioned that we had two to the power company chap and he said that is now the local code...

 

But the two ground rods are connected together with a large gauge wire. That is the difference. A larger gauge wire has less electrical "resistance".

And if your ground is frozen, I sure wouldn't want to be working on this project now (digging anything!)...

 

Can you just parallel the existing water line to get to the panel? The water line should not have its own rod.

Older codes used to allow the grounding connection to be anywhere on the metallic water line. Now it is required to be within 5' of where it enters the building.

 

once water and power are inside the basement, they are both on the same back wall and it will be easy to run a ground wire inside the basement the 30' or so... I hope an internal connection to the panel is legal.

 

Yes, the panel neutral buss would be the usual connection point.

 

I will have to wait for the ice and snow to melt away to confirm that the two rods are connected.

 

well I am back at the house again, today's reading is 16V AC. I forgot to bring a resistor to make the measurement that was suggested but I did bring the ground clamp I bought. I started looking at running a ground wire from the pipe to the main panel. The wire I have at hand is romex - thinking I could use the single copper ground wire or even all three wires in the romex.

Then I thought some more... why not simply connect the ground clamp to a wire that I take into the nearest power or light socket that runs a ground wire, of the same diameter, back to the same neutral panel ?

I understand that, in general, bigger wire is better and that three strands would be better than one.

But for my needs, surely a 14 gauge copper wire to the neutral panel will increase safely by drawing the current to the house neutral ?

The only thing I can think of is that I would now be placing the undesired current into a circuit that may have various appliances connected to it, but if the neutral in those circuits is properly connected to the neutral at the panel there would in fact be no difference...

I did also have a call back from the electric company engineer who said he was going to 'play in the street' looking all about for the source of the current but that finding it could be tough.

 

The Code requires the water line bond to originate in the panel, not at a point on the branch circuit wiring. The NM cable is not large enough to properly bond the service and water line. You are also prohibited from paralleling conductors smaller than 1/0.

I am going to suggest that you get some professional help along with the power company. Shock hazards are not to be taken lightly.

 

I am watching this thread and not very often I will say this .,,

I think it time for you stop right there and get a Electrician to come out and do the proper troubleshooting this is kinda tricky troubleshooting.

This is more than just a simple troubleshooting here.

Sorry for be little harsh but you have to understand the safety here.

Merci,Marc

 

As pointed out, the Romex is too small. The size of your water pipe grounding conductor is dictated by the size of your conductors feeding your main panel. Here is a quick rundown of table 250.66:

2/0-3/0 copper or 4/0-250kcmil Aluminum = #4
1-1/0 copper or 2/0 -3/0 AL = #6
2 or smaller copper or 1/0 or smaller AL = #8

The conductor should run from where the water pipes point of entry of the house is, continuously back to the main panel. If you have any breaks in the water pipe, like water meters, water heaters, or water softeners, they should either be connected to this grounding conductor with the proper clamps or you should install a jumper around the break in the water pipe.

Another thought, You mentioned you have an electric water heater. They sometimes leak current through a bad element. When you were testing did you kill the W/H with the disconnect?

 

Thanks Tolyn good info. This is what a DIY forum is all about.

 

Please let us know how it come out and useally some case with oddball grounding issue like your the electric waterheater is the curpit the last time I did troubleshooting in my customer house everything is fine in that house and do little leg work and found next door neghibour house have grounded electric waterheater and that person did try to find out why his electic bill is pretty high.

plus what more his underground cable from the house to his garage have pretty good size nick on the cable so it did affect the whole thing.

{ that part took me a pretty good part of day to troubleshooting plus POCO was willing to help me on this matter so it was a cordanited task.}

Merci.Marc

 

I bought 50' of the biggest gauge copper ground wire and I am installing it.

I connected one end to the neutral bar in the electrical panel and before I attached the other end to the water pipes I decided to measure the potential difference between the pipe and the new ground wire.. nothing significant. There is still 12V AC between the pipes and a support column standing on the concrete basement floor. There is also 12V AC between the neutral wire and the column. (Remember the current is present even when the house main breaker is open.)

This suggests to me that bonding the water pipes to the neutral bar is not going to get rid of the current. It further suggests that the current is coming from the neutral of the power company (or the steel column in my basement is the fabled free current generator I have been looking for for years... ) I will speak to the electric company again on Monday.

 

the saga continues...

I installed a heavy ground wire from the distribution panel to where the water pipes come into the basement. Current is still there.

In the meantime, the AC voltage is now around 33 Volts.

I disconnected the telephone ground wire. No change so i reconnected that.

I recently moved our hot tub. It had a loose ground wire in its sub-panel (so much for electricians). After disconnecting all 4 leads to the tub there was voltage between the tub wires and the ground at the sub panel. There was also still voltage between the water pipes and ground. So it was not the tub causing the problems. (After reconnecting the tub in the new location, with a proper ground - one can now feel the tingling in the tub water when one stands barefoot on the pressure treated deck. This makes sense as the tub is now properly grounded.)

This weekend I did some measurements in the house next door.
Sure enough, they also have 33 VAC between their ground wire and some rebar sticking out of their basement wall. So we called the electric company again. The chap that came out this time seems more knowledgeable. he said they have been having some load balancing (between the neural and two hot 120V lines) problems in the area and he had managed to reduce the imbalance recently. His theory is that their neutral (which is of course bonded the the ground wires) is high. He said there is no problem in our house.

I spoke the the chief engineer for the area again and he said they need to find which consumer is placing current into the neutral. I suggested they shut of areas until the problem goes away and then shut of power to each house in the problematic area until they find it. He agreed. There is a hydroelectric plant down the road that is also feeding current into the grid. I asked him to have their equipment checked.

He said they have neutral blockers but the blockers trip completely if there is more than 10 Volts on the neutral! He agreed that such a mechanism would only mask the problem anyway and that they need to find the source of the problem. I stressed that a child that walked off the road to get a drink from our faucet would likely get 33 Volts through their body.

 

I think you're absolutely right that this is a power company problem, and a pretty serious one at that. Keep pushing them until you get a resolution. Showing 33V on a well grounded conductor is really high.

 

I am sitting here wondering what would happen if the power company systematically shut off all the transformers in the area, one at a time, and took voltage readings after each transformwer was shut down.

 

It almost makes me wonder if they have a transformer hot shorted to the neighborhood's neutral somewhere. The impedance of the earth might be just enough to keep the primary fuse from burning.

 

The utility company is still struggling to find the problem! They have found some breaker somewhere that if opened, shuts off power to a large area and when open also removes the voltage from the neutral. So all that indicates is that the problem lies the other side of that breaker.

 

WOW almost 2 years later and they still haven't figured it out.

 

It doesn't sound like the power company considers this a high priority.

 

Last time I saw this it was a neighbors defective water heater. It's element put current on the cold/hot copper water line. The idea to kill the adjacent neighbors power, one by one is a good one. I suppose a well pump could do this as well.