Ground Rods

[Heron Longoria Jr.]

The Code (N.E.C) requires no more than 25 OHMS resistance to ground when you use "rod and pipe" electrodes.. which is pretty much what you see out on residential applications....and in my opinion, NO SOIL EXISTS THAT HAS A RESISTANCE THAT LOW.

So pretty much....2 rods are required everywhere...in my opinion, and is never the case out there.

My question is: Is the electrician "required" to test the OHMS? or is it the responsibility of the AHJ to test the OHMS and require the additional rod if the 25 OHMS is exceeded?

I beleive it is the responsibility of the "licensed" individual, (electrician), to test if "rod and pipe" electrodes are used not the Inspector. Or the electrician can use 2 rods at every service if the electrician cannot, or will not test the OHMS...

Any opinions?


Heron Longoria Jr.
Building Inspector
City or McAllen

[Jim Port]

It seems to be commonly accepted that the proof is on the contractor to show <25 ohms. Given the cost of the test equipment and scheduling the time with the inspector, it is easier and less costly just to drive two rods.

Are you dealing with metallic water lines from the city or a well? The metal water line from the city would be the primary electrode and the rod would be the supplemental electrode.

[Wayne Carlisle]

One thing you need to be aware of is that a lot of water lines being replace are using nonmettalic material and you lose your grounding source.

Watch for it and report insufficient ground to service panel.

[Heron Longoria Jr.]

Thanks Guys

The local plumbers are all pretty much installing PEX water piping...electricians are pretty much just using rod and pipe for residential service grounding electrodes...

I have a hard time proving to my Building Official that we need to require 2 rods unless they can prove > 25 OHMS...

I understand a revision in the 2011 NEC might address this problem..

[Jerry Peck]

My question is: Is the electrician "required" to test the OHMS? or is it the responsibility of the AHJ to test the OHMS and require the additional rod if the 25 OHMS is exceeded?


It seems to be commonly accepted that the proof is on the contractor to show <25 ohms. Given the cost of the test equipment and scheduling the time with the inspector, it is easier and less costly just to drive two rods.

That is basically how it is addressed: Either prove it or install the second rod.