IRC 2024 Grounding Electrode System: Ground Rods, Water Pipe, and Concrete-Encased Electrodes

Quick Answer

IRC 2024 Section E3607 requires a grounding electrode system (GES) for every residential electrical service. The GES must use all available electrodes at the building, including ground rods, metal water pipe (if metallic), and concrete-encased electrodes (rebar in footings, also called Ufer grounds). Ground rods must be at least 8 feet long and made of copper-clad steel or solid copper.

Under IRC 2024, if a single ground rod exceeds 25 ohms resistance to earth, a second rod is required. Modern homes with plastic (PEX) water supply piping must supplement the water pipe electrode with ground rods or a concrete-encased electrode.

What IRC 2024 Actually Requires

Section E3607 requires that the grounding electrode system be composed of all electrodes present at the building that meet the definition of a grounding electrode under the NEC. The IRC intentionally requires the use of all available electrodes because the parallel combination of multiple electrodes produces a lower system impedance than any single electrode, improving the effectiveness of the grounding system for both lightning protection and fault current clearing.

The metal underground water pipe electrode is one of the most important components of the GES. A metal water pipe that extends at least 10 feet into the ground provides an excellent electrode because the pipe’s large surface area in contact with moist soil creates a very low-impedance path to earth. However, IRC 2024 (following NEC 2023) recognizes that metal water pipes are increasingly being replaced with plastic piping (PEX or CPVC), and that a plastic water pipe does not function as an electrode. When the water supply pipe is plastic from the street to the building, or when a plastic-to-metal transition occurs within 5 feet of the building, the water pipe electrode cannot be relied upon and must be supplemented by other electrodes.

Concrete-encased electrodes (CEE), commonly called Ufer grounds, are considered the most effective type of grounding electrode by most electrical engineers. A CEE consists of at least 20 feet of AWG 4 or larger copper wire, or at least 20 feet of 1/2-inch or larger steel reinforcing bar (rebar) embedded in the concrete footing of the building. The concrete and the moisture in the surrounding soil create a very large effective electrode surface area. IRC E3607.5 requires a CEE where a CEE is available — meaning that any building with a concrete footing should use a CEE as part of its GES.

Ground rods, if used, must meet the specifications in E3607.4: at least 8 feet long, and made of copper-clad steel (minimum 0.010-inch copper cladding) or solid copper. Iron or steel rods are not permitted because they corrode and lose conductivity over time. The rod must be driven vertically to its full length, or at up to a 45-degree angle if rock or other obstructions prevent vertical installation. If the resistance of a single rod exceeds 25 ohms (measured with a ground resistance meter), a second rod must be installed and connected in parallel.

Why This Rule Exists

The grounding electrode system serves two distinct electrical functions. First, it limits the voltage difference between the electrical system and the earth during normal operation and during lightning events. Second, it provides a low-impedance return path for fault current when insulation failure causes line-to-ground contact, allowing the over-current protective device (fuse or breaker) to operate and clear the fault. A high-resistance grounding system may not provide enough fault current to trip the breaker, leaving the faulted equipment energized at a dangerous voltage.

The requirement to use all available electrodes reflects a defense-in-depth philosophy: no single electrode is infallible. Ground rods can corrode. Water pipes can be replaced with plastic. Footings can crack. Using all available electrodes in parallel ensures that the GES remains effective even if any single electrode degrades over the life of the building.

What the Inspector Checks at Rough and Final

At rough-in, where the Ufer ground is the primary electrode, the inspector verifies that the conductor embedded in the concrete meets the minimum length and material requirements, and that the conductor exits the footing at the correct location for connection to the grounding electrode conductor (GEC) that runs to the service panel. This verification must occur before the concrete is poured — after pouring, there is no way to inspect the embedded electrode.

At final, the inspector verifies that all required electrodes are bonded together with the grounding electrode conductor of the correct size (typically AWG 6 copper for 200-ampere services), that the GEC connection to the main panel is properly made at the neutral bar, that the main bonding jumper is in place, and that the ground rods are driven to their full depth and connected with listed clamps rated for direct burial.

What Contractors Need to Know

The concrete-encased electrode must be connected before the footing pour. This is a coordination issue between the electrical contractor and the concrete contractor. A missed CEE requires installing ground rods as a substitute, which is a less effective electrode and may require two rods to meet the resistance requirement. Build CEE installation into the pre-pour checklist and verify it before the concrete truck arrives.

The grounding electrode conductor from the panel to the ground rods or CEE must run continuously without splices (except at the electrode connection itself). Where the GEC runs through or along a wall, it must be protected from physical damage. Where the GEC runs through a metal enclosure, it must bond to that enclosure to prevent inductive heating of the GEC.

Modern homes with PEX water supply piping require additional electrodes to compensate for the loss of the water pipe electrode. At minimum, two ground rods (if only rods are used) or one rod plus the CEE are required. If the home has only a CEE and the water supply is plastic, the CEE alone may be sufficient if it meets the 20-foot minimum length requirement.

What Homeowners Get Wrong

Homeowners who upgrade from a metal water supply pipe to PEX often do not realize that this change eliminates a component of their grounding electrode system. A plumber who replaces a section of galvanized iron supply pipe from the meter to the water heater with PEX may inadvertently interrupt the continuity of the metal water pipe electrode, reducing the effectiveness of the GES without the homeowner or the plumber realizing it. If you replace your water supply piping with plastic, inform your electrician so the GES can be evaluated.

Another misconception is that the ground rod alone constitutes a complete GES. A single 8-foot copper-clad ground rod is a permitted electrode, but if its resistance to earth exceeds 25 ohms (which is common in dry or rocky soil), a second rod is required. Skipping the resistance test and assuming compliance is a code violation.

State and Local Amendments

Some jurisdictions in areas with poor soil conductivity (sandy, dry, or rocky soils) have adopted requirements for a minimum of two ground rods regardless of resistance, rather than the one-rod-if-under-25-ohms approach of the IRC. This eliminates the need for resistance testing and ensures a more robust GES in challenging soil conditions.

California and several western states with corrosive soils have adopted provisions specifying minimum rod diameter or cladding thickness requirements beyond the IRC minimum, to ensure adequate corrosion resistance over the life of the installation.

Bonding vs. Grounding: A Critical Distinction

The terms “grounding” and “bonding” are frequently confused, even by experienced tradespeople, but they serve different purposes and are governed by different code sections. Understanding the distinction is essential for both correct installation and for interpreting inspection findings.

Grounding (more precisely, earthing) connects the electrical system to the earth through the grounding electrode system. The purpose is to limit the voltage of the electrical system relative to ground during normal operation and during transient overvoltage events such as lightning. The grounding electrode system — ground rods, water pipe, concrete-encased electrode — is the grounding pathway. The grounding electrode conductor (GEC) is the conductor that connects the neutral bus in the service panel to the electrodes.

Bonding, by contrast, connects metallic components together to eliminate voltage differences between them. Bonding does not necessarily connect to the earth — it simply ensures that all metallic surfaces a person might simultaneously contact are at the same electrical potential. IRC E3609 requires that gas piping, metal water piping, structural steel, HVAC ductwork, and all other metallic systems in the building be bonded to the electrical system. This bonding is what prevents a fault in the electrical system from making a gas pipe, water pipe, or duct system energized at line voltage.

The main bonding jumper in the service panel is the single point where the grounded (neutral) conductor is bonded to the equipment grounding conductor and to the panel enclosure. This bonding is only made at the main service panel — it must never be replicated at subpanels, where the neutral bus must be isolated from the enclosure. A subpanel with a bonded neutral is a common wiring error that creates a parallel return path for current and can result in current flowing on metallic building components during normal operation.

Common Violations Found at Inspection

• Concrete-encased electrode not installed before the footing pour, forcing the use of supplemental ground rods as a substitute
• Ground rod driven only partially to depth, with several inches protruding above grade and not at full 8-foot embedment
• Water pipe bond absent — the metal water pipe electrode is present but not connected to the grounding electrode conductor at the service panel
• Single ground rod installed without resistance testing in soil known to have high resistivity, potentially exceeding the 25-ohm threshold requiring a second rod
• Grounding electrode conductor spliced in the middle of its run without a listed irreversible compression or exothermic weld connection
• PEX water supply installed by plumber without notification to electrician, eliminating water pipe electrode without adding supplemental electrodes
• Ground rod clamp installed on rod above grade rather than at grade or below, where it is exposed to mechanical damage and corrosion