What is the green screw in my electrical panel?

The green screw is the main bonding jumper in many residential panels. When threaded in, it connects the neutral bus bar to the metal panel enclosure, bonding the grounded conductor to the equipment ground. This screw should only be installed in the main service panel, never in a subpanel.

Why is there a wire clamped across my water meter?

That wire is a bonding jumper. It bridges the water meter to ensure that the grounding path through the metal water piping is not interrupted by the meter body or its non-conductive gaskets. Removing this jumper can break the grounding path for the entire electrical system and is a serious code violation.

Does gas piping need a bonding jumper?

Yes. The NEC requires that the metal gas piping system be bonded to the grounding electrode system. This is typically accomplished with a bonding jumper connected to the gas pipe near the meter or appliance connection using a listed grounding clamp. The bonding jumper prevents the gas pipe from becoming energized during an electrical fault.

What size bonding jumper do I need?

The required size depends on the application. Main bonding jumpers are sized per NEC Table 250.66 based on the service entrance conductor size. Equipment bonding jumpers follow NEC Table 250.122 based on the overcurrent device rating. A licensed electrician can determine the correct size for your specific installation.

Can I use any wire as a bonding jumper?

No. Bonding jumpers must be copper or listed copper-clad aluminum and must be connected with listed grounding clamps or connectors. The conductor must be sized per NEC tables and must be continuous without splices unless the splice uses a listed irreversible compression connector. Standard wire nuts are not acceptable for grounding splices in many applications.

Bonding Jumper — Electrical Continuity and Code Compliance

A bonding jumper is a short conductor or metal strap that connects two grounding points to ensure electrical continuity across a joint, fitting, or piece of equipment.

Bonding Jumper diagram — labeled parts and installation context

What It Is

A bonding jumper is a dedicated conductor that bridges a gap in the grounding path where mechanical connections alone cannot guarantee reliable electrical continuity. In an electrical system, bonding ensures that all metal components — conduit, enclosures, water pipes, gas pipes, and equipment frames — are connected to the same ground reference. If a fault occurs, bonding provides a low-impedance path for fault current to flow back to the source, which trips the breaker and clears the fault.

Without proper bonding, metal components can become energized during a ground fault and remain at a dangerous voltage because there is no reliable path for fault current. The bonding jumper eliminates this risk by creating a permanent, low-resistance connection between components that might otherwise rely on loose mechanical contact.

Types

Main bonding jumpers connect the neutral bus to the equipment grounding bus inside the main service panel. They can be a wire, a bus bar, or a screw (the green bonding screw found in many residential panels). Equipment bonding jumpers are external conductors that bridge around a fitting or section of raceway where the mechanical connection does not provide reliable grounding continuity.

Supply-side bonding jumpers connect the service entrance equipment to the grounding electrode system. Water pipe bonding jumpers bridge around water meters, dielectric unions, and other fittings that could interrupt the grounding path on metal water piping. Gas pipe bonding jumpers connect the gas piping system to the grounding electrode system as required by code.

Bonding jumpers come in bare copper, green insulated copper, and braided copper strap configurations, with sizes determined by the circuit or service rating they protect.

Where It Is Used

Bonding jumpers are found at the main electrical panel (the green bonding screw or main bonding jumper strap), at water meter installations where a jumper bridges the meter to maintain pipe grounding continuity, at gas meter sets where a bonding clamp connects the gas pipe to the grounding system, and at swimming pool and hot tub installations where equipotential bonding connects all metal components within reach.

In commercial and industrial settings, bonding jumpers appear at conduit connections through expansion fittings, at transformer installations, and at any point where the raceway grounding path is interrupted by a non-conductive fitting or flexible connection.

How to Identify One

A bonding jumper is a bare or green-insulated copper conductor, wire, or braided strap connecting two metal components. At the water meter, it looks like a short piece of heavy copper wire with clamps on each end, bridging from the street-side pipe to the house-side pipe. In the electrical panel, it is either a green screw threaded into the neutral bus or a short copper bar connecting the neutral bus to the enclosure.

Equipment bonding jumpers are visible as green wires running alongside or inside conduit, connecting the conduit system to the grounding bus. Braided bonding straps are flat, flexible copper conductors used where rigid wire would be impractical.

Replacement

Replacing a bonding jumper requires matching the conductor size to the circuit or service it protects, as specified in NEC Table 250.66 for grounding electrode conductors and NEC Table 250.122 for equipment grounding conductors. The replacement conductor must be copper (or copper-clad aluminum in some applications) and must be connected with listed clamps, lugs, or connectors approved for grounding use.

Water pipe bonding jumpers should be inspected whenever plumbing work replaces a section of metal pipe with plastic, as this can interrupt the bonding path. A permit is typically required for any work involving the main bonding jumper or service grounding since these are critical safety components of the electrical system.