Grounded to the Water?!?!? - ECN Electrical Forums

Please forgive the homeowner-type question. I'm a VDV installer, and I've already asked the pro electrician in the family:

My house was built in 2000, with a 200amp lateral-fed service. There is a stranded aluminum GEC running to the area where the water service enters the basement and a #6 copper running out to a buried rod.

That's reasonable. But wait. The water service is via plastic pipe and there is a compression fitting transition to copper 2 inches upstream of the ground clamp for the GEC. There's no way an electrician could miss the pipe being plastic.

I asked the family pro (industrial and motor control, high-volt, etc) about this. His answer was that "You're grounding to the water system, not the pipe, so it's fine".

I'm confused. I seems to be a violation of the NEC as I read it, and I was under the impression that water was not a particlarly good conductor, as compared to metal and earth. Can anyone explain the rationale behind this installation?

I can't tell you anything about your place because I haven't seen it ... however ... here's a true story:
My house is built literally into a mountain. It's vintage ~1790. The well was dug (~285') into the mountain in 1973. When I moved in (1988) I replumbed the entire house in CPVC and PVC because the minerals in the water had rotted thru the copper to the point of constant pinholes in the type M copper (heavy wall). The copper was put in in 1973 along with the well. Every last piece is now plastic except a 12" nipple at the (gas) water heater in and out couplings due to the heat. In 1997 I tore out the old fuse box and put in a main breaker panel. The AHJ wanted a #6 to the water heater to ground the water itself. His argument was that there were so many minerals in the water that it became a good enough conductor to cause a problem. He told me that this was a common problem in the area. (Yes, I had the water checked by the county health dept and they declared it safe to drink). It was easier to comply than argue. In 2004 I did my neighbors house and the county still wanted this #6.

Slorch, I agree with the family pro, in your case the water pipe doesn't meet the criteria of being a Gounding Electrode and doesn't sound as though it is being used as such.

From the 99 NEC

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250-50(a) Metal Underground Water Pipe A metal underground water pipe in direct contact with the earth for 10ft (305m) or more (including any metal well casing effectivly bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or sections of insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors.

Any Metalic Water Piping must be bonded though.

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250.104 Bonding of Piping Systems and Exposed Structural Steel
(A) Metal Water Piping The metal water piping system shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible.
(1) General Metal water piping system(s) installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3).

If I understand correctly, the installation is OK.

Roger

[This message has been edited by Roger (edited 12-01-2005).]

"You're grounding to the water system, not the pipe...

No, you are grounding the water system.

The wire is there to bond the copper system in the house to the service ground, not to provide a ground for the service as would be the case if there were a metallic water supply line.

And you need another ground rod. [Linked Image]

-Hal

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There is a stranded aluminum GEC running to the area where the water service enters the basement and a #6 copper running out to A buried rod

The water pipe doesn't meet the criteria of being a Gounding Electrode and doesn't sound as though it is being used as such... So, by code, shouldn't a 2nd ground rod have been installed in in this installation to acheive 25ohms or less?

Hbiss - You beat me! J

Plastic or metal water supplies he still needs two rods unless he can prove less than 25 ohms.

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The wire is there to bond the copper system in the house to the service ground, not to provide a ground for the service as would be the case if there were a metallic water supply line.

And you need another ground rod.

The fog is lifting a bit. I was assuming the system was setup to use the water line as the main electrode. It "looks" identical to such a system (AL conductor is connected to the panel's ground lug, while the #6 copper occupies a lug in the ground bar, no evidence of a 2nd rod, etc.). I assumed the #6 was for the required supplemental rod in such a system, when in fact it is the GEC.

So, if the bonding conductor is clamped on the "outboard" side of the meter, should the meter be jumpered to maintain continuity to the rest of the indoor plumbing? Right now it's plastic to compression fitting to copper w/AL clamped, then meter and remainder of indoor copper piping. No jumper over the meter.

In my defense, there is plenty of evidence of shoddy workmanship throughout the house, and with small children thrashing about, I'm wary. I've also been told I'm a little slow on the uptake... [Linked Image]

Since we weren't there in 2000 when the service was inspected we don't know if the rod did infact meet 25 ohms or less, or if it didn't. [Linked Image]

Roger

sounds like you are using a well and not a city water supply, so you should have 2 ground rods, and you also need to have #4 copper not #6..

Makokiller, can you give an NEC reference to where it is required to have a #4 to the rod or rods?

Might you be thinking about a local code?

Roger

look at the chart 250.66 he said that he has a 200amp service.. do the math

Mako take a look at 250.66(A) and do the reading. [Linked Image]

Mako, as with any part of the NEC you must read the whole article, you can not stop at one section or table.

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250.66 Size of Alternating-Current Grounding Electrode Conductor
The size of the grounding electrode conductor of a grounded or ungrounded ac system shall not be less than given in Table 250.66, except as permitted in 250.66(A) through (C).

Here is the kicker.

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250.66(A) Connections to Rod, Pipe, or Plate Electrodes Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or (A)(6), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.

Roger

so let me get this straight.. you could use #6 copper for your city water pipe connection, and your ground rods??? even for lets say a 300amp service??

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so let me get this straight.. you could use #6 copper for your city water pipe connection, and your ground rods??? even for lets say a 300amp service??

To the rod yes, to the water line it would be sized directly from table 250.66.

Put a 4000 amp service in a field and you will only need a 6 AWG CU to one or two ground rods.

now that is what i thought.. when do 300 amp services, I run #4 to the rod and #2 to the water meter, and thanks, with the price of copper nowadays it will save me some money..

Mako, as Iwire points out, which is the point of this thread, the connection to the rod(s) only need be a #6 copper regardless of the size of the service.

In this thread the water piping is not part of the GES.

Roger

Mako, sorry, you posted while I was typing.

Roger

I think you need to bond the water line ( Key Word ) and ground 2 rods