Yes, your described grounding electrode system appears to be compliant with the NEC, specifically based on your description and reference to 250.66(A) and the handbook illustration. Let's break it down: Existing 2/0 GEC to Water Pipe

This satisfies the requirement for a metal underground water pipe electrode (250.52(A)(1)). The 2/0 size is likely appropriate for a 600A service, determined by 250.66 based on the size of your service entrance conductors.

Adding Two Ground Rods

This supplements the water pipe electrode as required by 250.53(D)(2) which states "Supplemental Electrode Required. A metal underground water pipe electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). Where the supplemental electrode is a ground rod...".

6 AWG Jumper to Ground Rods

You are using a 6 AWG conductor to connect the two new ground rods to the existing 2/0 GEC. You are correct that 250.66(A) allows the ground rod portion of the grounding electrode conductor to be sized per the following: "The portion of the conductor that is the sole connection to one or more ground rods, ground plates, or ground cones shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire".

Split Bolt Connection

As long as the split bolt is listed for direct burial (UG), it is compliant for this application.

Why the Inspector Might Be Disagreeing and How to Address It


Misunderstanding of 250.66(A)

The inspector might not be fully grasping the exception in 250.66(A). Emphasize that the only connection to the ground rods is the 6 AWG. If you were connecting to, for example, a building steel electrode in addition to the rods, then you would need to consider the size of conductor required by 250.66.
2.

Concern About the Water Pipe as Sole Electrode

The inspector might be concerned that the water pipe could become the only electrode if it becomes electrically discontinuous (e.g., replaced with PVC). However, that's why the NEC requires a supplemental electrode. The intent is that the supplemental electrode is always there.3.

General Skepticism

Some inspectors are simply more cautious or have different interpretations.

How to Handle the Situation



Politely Explain Your Rationale

Clearly explain your understanding of the code, referencing 250.66(A) and the handbook illustration.

Show the Handbook Illustration

If you have access to the NEC Handbook, show the inspector the illustration that supports your method.

Ask for Specific Code References

If the inspector still disagrees, ask them to provide the specific code section they believe is being violated. This forces them to justify their position.

Escalate (if necessary)

If you cannot reach an agreement, ask to speak with the inspector's supervisor or the head of the inspection department. Document your conversations.*

Request a Formal Interpretation

If you still can't reach a resolution, you can request a formal interpretation of the code from your local electrical authority or, in some cases, the NFPA (National Fire Protection Association).

In summary, your plan appears code-compliant. The key is to clearly communicate your understanding of the relevant code sections and be prepared to back it up with documentation. Flag for review