Water service pipe grounding ?

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Old 05-02-08, 12:11 PM
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Water service pipe grounding ?

Iím replacing my 20 foot water-service pipe from my well-pit to basement with plastic (black poly). Iím also replacing the parallel pipe containing the submersible pump motor wires with PVC. Both were galvanized steel and separated underground by about 2 inches. Is grounding an issue?

The water pipe connected to copper inside the house. The pipe for the motor wires just stuck 3 inches out of the wall and three 12 AWG motor wires came out and up about 12 inches into the motor control box. The pipes were 40 inches below grade and when I dug them out I noticed a metal rod (still there) stuck in the ground between the pipes about 4 feet from the house. It stuck out about a foot above the pipes. I think it was touching the pipe for the motor wires- but not the water pipe. (Wish now I had noted more carefully).

Is that pipe some kind of grounding rod? . It wasnít fastened to anything Ė just touched a pipe? (I think). If the cold water supply pipe to the house is supposed to be a ground and you replace it with plastic, what are you supposed to do? I have the NEC but that area is difficult for me.

Any info would be greatly appreciated!
 
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Old 05-04-08, 02:50 PM
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Your water pipe was used as a grounding electrode and met the NEC requirement. Now that the pipe has been replaced with plastic, it no longer meets the requirement to be used as a grounding electrode. The good news is that the water pipe was required to be supplemented with 1-2 ground rods...one of which you saw. What you need to have now is probably 2 ground rods with a #6 Copper going back to your main panel. You have 2 options:

1) If you only have one ground rod then the ground resistance has to be measured to be below 25 ohms.

2) If you have 2 ground rods, that's it, you're done, but make sure you have a #6 Cu going back to your panel.
 
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Old 05-05-08, 01:24 PM
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Thank you very much dzdave00.

Donít know whatís relevant here but my basement is 30 feet wide and my service panel sits in one corner and 30 feet away in the other corner is where the 20 foot water line came into my basement. I believe my panel is large enough for 200 amps although the house has 100 amp service. Before the service panel is another shutoff box that feeds the service panel and thatís where the electric service line from the company connects. There is a clamp on the cold water pipe about 2 feet from that shutoff box with a heavy copper wire running into the shutoff box.

I just checked now and was surprised. There was a second identical copper wire coming out of the shutoff box and I followed it and follows the electric service cable. It runs back outside about 6 feet and connects with a clamp to a rod in the ground. I never noticed that until now since the view of the rod was obstructed by the oil tank filler pipe.

But the other rod that was buried underground near my water service pipe did not have any clamps or wires and I donít believe it was touching the water pipe Ė but it might have been. (If thatís relevant). It looks to be steel and I thought it was just something to keep a pipe in line.

But if I understand you if that ground resistance measures below 25 ohms on that single rod thatís outside about 6 feet from my service panel - Iím Ok. Is that measurement something a DIYíer can do?

Would you use that second rod in the ground near the water line and run a #6 copper wire back to the shut-off box? That rod is about 4 feet outside the basement wall and another 30 feet across the basement to the service panel. Or is that incorrect since the top of that rod is about 30 inches underground? I could clamp a copper wire on it and get it back through the wall from the outside since Iím putting new pipes through the opening anyway. Or would you just find another place to put a second rod is needed?

Any of your thoughts would be appreciated!
 
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Old 05-06-08, 06:16 PM
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The steel pipe in the ground cannot be used as a grounding electrode. Your best bet (cheapest) to be code compliant is to install a second ground rod and connect it to the other one with acorn clamp. Make sure the new rod is buried at least 6 feet from the first rod. You could measure the resistance yourself if you had the proper equipment, but it is expensive.
 
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Old 05-07-08, 08:10 AM
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Thanks again dzdave00!

Of course- thatís a great and simple solution. Glad you answered ! I understand what you are saying. Sure!- thatís guaranteed to be code compliant and it sounds like even I certainly could do it. So thatís what Iíll do. Iíll install the second ground rod the way you suggest. Thanks a lot again.
 
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