Grounding & Bonding
~12 min read · Explain electrodes, water-pipe and gas bonding — and why grounding differs from bonding.
Grounding and bonding are the fault's homeward path: electrodes tie the system to earth, bonding ties every metal part together, and the goal is a low-resistance loop that trips the breaker instantly when a hot wire touches a chassis. The inspector traces the visible parts of that loop.
The electrode system
The grounding electrode conductor (GEC) runs from the service neutral to the electrode(s): driven ground rods (modern practice pairs them), metal water-pipe electrode (bonded within the first few feet of entry — with a jumper around the meter), concrete-encased electrode (Ufer) in newer builds. Inspect: GEC present, continuous, clamped with listed connectors (acorn clamps ON the rod, not lying beside it), corrosion, and severed or landscaping-damaged conductors. Plastic water-service replacements silently delete the water-pipe electrode — a finding when the rod system is absent too.
- GEC from service to rods/water pipe/Ufer
- Listed clamps, tight, corrosion-free; jumper around the meter
- Plastic pipe replacement can orphan the old electrode
Bonding: the fault path
Bonding connects metal parts so a fault energizes the breaker, not a person: the main bonding jumper (service), equipment grounding conductors to every device, metal water and gas piping bonded (gas commonly via the equipment grounding of its appliance circuit; CSST flexible gas tubing demands its own listed bonding — lightning-induced arcing perforates unbonded CSST), and pools/spas with their own grid. The purpose is clearing FAULTS — earth itself is a lousy conductor; the trip current flows on the bonding path back to the source.
- Bonding clears faults; electrodes handle lightning/stability
- Water and gas piping bonded; CSST needs listed direct bonding
- Fault current returns on wires, not through dirt
Receptacle-level truth
Three-light testers report the story's end: open grounds (three-prong receptacles on two-wire circuits — common in mid-century homes; remedies: real grounding, GFCI-with-label, or two-prong restoration), bootleg grounds (neutral jumped to ground at the device — dangerous fakery that testers can miss but which energizes chassis under fault), reversed polarity, and open neutrals. Systemic open grounds in an older home get reported as an era condition with upgrade paths, not as a hundred individual defects.
Worked example
A 1958 home with recent 'updates': every receptacle is a modern three-prong, but the tester shows open ground at most; two read grounded in a room where cloth two-wire cable is visible in the basement below; the GEC clamp lies detached beside a rusted ground rod; and the water service was replaced with PEX last year. The gas system includes yellow CSST with no visible bonding jumper. Build the grounding report.
Start at the electrodes: a detached clamp means the rod system is disconnected, and the PEX replacement erased the water-pipe electrode — the service currently has NO functional grounding electrode: correction required. The receptacles: three-prong devices on two-wire cloth circuits explain the open grounds (era condition — remedy options: rewire, or GFCI protection with 'No Equipment Ground' labels); the two that read 'grounded' above two-wire cable are prime bootleg-ground suspects — a hot-to-chassis fault there electrifies the appliance; flag for electrician verification. The CSST: unbonded yellow CSST is a lightning-perforation fire risk — listed bonding jumper required. One narrative: the house LOOKS grounded at every level and functionally is grounded at almost none — which is precisely the finding.
Common exam pitfalls
Trusting three-prong receptacles as evidence of grounding.
Devices are cheap; conductors are the truth — test, and correlate with visible wiring era.
Believing earth clears faults.
Rods stabilize and shed surges; FAULTS clear on the bonding path back to the source — that's why bonding integrity matters most.
Overlooking CSST bonding.
Yellow CSST without its own listed bonding is a known lightning-fire mechanism — a specific, reportable finding.
Rods for the sky, bonds for the fault, wires all the way home — and never let a receptacle's face vouch for its wiring.
Recap
- GEC + electrodes (rods, water pipe, Ufer) tie the system to earth
- Bonding clears faults; earth doesn't
- Water/gas bonded; CSST requires listed direct bonding
- Open grounds: era condition with defined remedies
- Bootleg grounds: dangerous fakes — verify suspicious 'grounded' readings
- Detached clamps and orphaned electrodes = service-level findings
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