Okay, let's break down the grounding requirements according to the NEC (National Electrical Code) and address your specific situation.

Understanding the Requirements Grounding Electrode System (GES)

The GES is a system of interconnected electrodes (like ground rods, metal water pipes, concrete-encased electrodes) that provides a low-impedance path to earth. Its purpose is to stabilize voltage to ground during normal operation and, more importantly, provide a path for fault current to return to the source (the transformer), causing the overcurrent device (breaker or fuse) to trip.

Metal Water Pipe Electrode

A metal underground water pipe in direct contact with the earth for 10 feet or more is a very effective grounding electrode. It must be supplemented by another type of electrode.

Ground Rods

Ground rods are a supplemental electrode and must be at least 8 feet long and spaced at least 6 feet apart.

Main Bonding Jumper (MBJ)

This jumper connects the equipment grounding conductors (the green wires in your circuits) to the neutral (grounded) conductor at the service equipment (your main panel). This connection is only made at the service equipment.

Bonding

Bonding refers to the process of connecting metallic parts that are likely to become energized during a fault, creating a low impedance path for fault current back to the source.

Your Specific Scenario

You have a #4 copper conductor intended to connect the ground rods to the GES. Your metal water pipe is near the ground rods.

The Correct Method (according to NEC)

You cannot run a jumper from the water pipe to the ground rods then to the panel as a single continuous run. This would not meet code.Here's how you should do it, and why:1. Connection to Panel

Run a #4 copper conductor from the ground rods to the service panel grounding bus.2.

Separate Connection for Water Pipe

Run a separate #4 copper conductor from the metal water pipe (within the first 5 feet of entry into the building) to the service panel grounding bus.

Why Separate Connections? NEC Compliance

The NEC requires that each grounding electrode be connected individually to the grounding busbar in the service equipment, or be connected to a common grounding electrode conductor, as described in 250.64(C).

Redundancy

By running separate conductors, you maintain redundancy in your grounding system. If one connection becomes compromised, the other electrode can still provide a grounding path.

Important Considerations Water Meter Bonding

If your water meter is between the point where the water pipe enters the building and your grounding connection, you must install a bonding jumper around the water meter. This ensures electrical continuity even if the meter is removed. The size of this jumper is based on the service entrance conductor size. If you're using #4 copper for the grounding electrode conductor, the bonding jumper should be at least #4 copper as well (see NEC table 250.66).

Clamps

Use listed and labeled grounding clamps suitable for direct burial and compatible with copper conductors and the materials you're connecting to (copper pipe, steel ground rods). Make sure they are tightened properly.

Burial Depth

Bury the grounding electrode conductor and ground rods to the proper depth per local code. Ground rods typically need to be driven at least 8 feet into the ground, leaving no more than a few inches exposed for the connection.

In summary, run two separate #4 copper conductors

1. From the ground rods to the service panel grounding bus.
2. From the water pipe to the service panel grounding bus.3. Bond around the water meter if it exists between the grounding point and the earth.

Disclaimer: I am an AI chatbot and cannot provide electrical advice. This information is for general knowledge and educational purposes only. Always consult with a licensed electrician for electrical work to ensure safety and compliance with local codes. Flag for review