4

My 200A main panel ground currently goes to the metal water pipe right where it comes into the building. Presumably the pipe was allowed as the only grounding electrode when the system was installed years ago. But the wire to it is not right – it appears to be three pieces of #10 twisted together, in conduit – so I thought I'd replace it with what's really required which is #4.

However, if I read the code correctly, 250.53(D)(2) now requires a supplemental electrode like a ground rod (or, if necessary, two) when a water pipe is used. And if a water pipe is not used, a ground rod (or two) or other permitted electrode is required anyway by 250.52(A) and 250.53(A). So it seems like the water pipe is useless as a grounding electrode, since you have to install the same other electrodes that you would need without it.

It also appears that 250.104(A) requires bonding the metal water pipe to the GEC using the same size conductor that would be required if it were used as a grounding electrode. The only difference is that that connection does not have to be within 5' of where the pipe enters the building, as would be required if using the metal water pipe as a grounding electrode.

Are these understandings correct or am I missing something here?

Thanks,

Tom

2
  • 3
    Think these days it is more to provide a ground for the plumbing, than ground for the electric system. Of course these days the plumbing system might be all or mostly plastic.
    – crip659
    Sep 8, 2022 at 22:10
  • Your reading is correct based on my modestly deep reading about earth grounding code over the past year.
    – Armand
    Sep 11, 2022 at 3:35

2 Answers 2

1

A lot varies by jurisdiction. But in my experience (one instance, but very recent) with a professional electrician and inspection:

  • Water pipe, ground connected where pipe comes into the building (i.e., before any valves/fixtures/etc.) plus a single ground rod.

That is important because if any pipes inside the house are replaced with plastic then the connection would be useless. The old ground wire was connected just past the water heater, so if my plumber had replaced pipes with plastic when we had pinhole leaks many years ago (it was a huge problem in my area for several years presumed, but never officially confirmed, due to chemicals used to treat the drinking water) then I would have lost ground and had no idea.

  • Two ground rods.

My electrician was actually prepared with ground rod and tools in case the inspector required a second ground rod - no use arguing when some places require two ground rods even with water pipe connection. But he said that other local jurisdictions that always require two ground rods have a lot more plastic water pipes and do not require the water pipe connection.

In other words, the point is to have two good grounds. Copper pipe through the ground to the meter (in my area that would typically be 20 feet or so) is arguably just as good as a ground rod, if not better. In fact, this setup is actually more redundant than two ground rods because two ground rods normally come from a single wire going to the panel. With water pipe + ground rod, there are two ground wires - one inside to the water pipe and one outside to the ground rod.

0

Agree that the water pipe is essentially useless these days, when the various plastic materials are generally used.

Further, that effective grounding is absolutely ESSENTIAL. Two ground rods, connected with #4 solid copper will take car of the issue. When the tops of mine were to be covered with concrete when a pad was poured, I coated the connectors heavily with a tar compound to prevent corrosion.

Lack of a good ground will cause all kinds of problems with lightning strikes even a mile away. Popped light bulbs, damaged electronics, etc. A whole house surge suppressor is also a good idea.

2
  • 1
    Welcome to Home Improvement. If you'll take the tour, you'll see that this is a Question & Answer board, not a general discussion forum. While your points are valid, they don't actually answer the question asked. If you'd care to edit this into an actual Answer, that would be fantastic!
    – FreeMan
    Sep 10, 2022 at 12:56
  • Also, if you want effective grounding, you put an Ufer (concrete-encased electrode) in when the foundation is poured then call it done Sep 10, 2022 at 13:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.