You are correct; the answer is likely yes, but with a couple of important considerations and potential code references. Here's a breakdown of why, and what to watch out for

Why likely YES:
Common Grounding Electrode System

The intent of the National Electrical Code (NEC) is to create a unified grounding electrode system. If you're connecting to a water pipe (which is a grounding electrode), and then running a grounding electrode conductor (GEC) from that to a ground rod, you are essentially bonding the water pipe electrode with the ground rod electrode. This creates a more robust grounding system.

Equipotential Bonding

The fundamental principle is to create an equipotential plane. The purpose of the GEC is to bond all grounding electrodes together, preventing voltage differences between them. Connecting the ground rod to a point on the cold water pipe already tied to the first service effectively connects the ground rod to the entire water pipe grounding electrode system.

Important Considerations and NEC References



NEC 250.50 Grounding Electrode System. This section mandates the creation of a grounding electrode system. This implies interconnection. NEC 250.52 Grounding Electrodes. This section lists acceptable grounding electrodes. You need to make sure both the water pipe and ground rod meet the requirements of this section. Specifically regarding the water pipe: (A)(1) Metal Water Pipe. The metal water pipe must be in direct contact with the earth for 10 ft or more. Also, the metal water pipe must be supplemented by an additional electrode. NEC 250.64 Grounding Electrode Conductor Installation. This section covers the requirements for the GEC. The critical part for your situation is: (C) Continuous. Grounding electrode conductors shall be installed in one continuous length without a splice or joint, unless spliced by listed irreversible compression-type connectors or by the exothermic welding process. (F) Grounding Electrode Connections. Grounding electrode conductors and bonding jumpers shall be connected to grounding electrodes in a manner that will ensure a permanent and effective ground. Where grounding or bonding equipment is installed by means of bolts, screws, rivets, or similar means, the member shall be mechanically secured to the equipment or structure. Grounding locknuts or grounding bushings shall not be the sole means of securing bonding jumpers to enclosures. Integrity of the Connections

Ensure all connections are tight, corrosion-free, and properly rated for the application. Use listed connectors designed for grounding.

Local Amendments

NYC often has amendments to the NEC. Always check with the NYC Department of Buildings for any local variations or interpretations of the code.

Why your Assumption is Correct (Generally)

The fact that the ground rod is connected to one of the water pipe connections already bonds the ground rod to the water pipe system. Since both service switches are independently grounded to the same water pipe system, the ground rod effectively becomes part of their grounding system as well.

Important Disclaimer:

I am an AI chatbot and cannot provide electrical code interpretations or guarantees. This information is for educational purposes only. Always consult with a licensed and qualified electrical contractor in NYC for any electrical work or code compliance issues. They can assess the specific installation and ensure it meets all applicable codes and regulations. They can also verify that the existing installation is safe and compliant. Flag for review