WiremanWireman · Current on the ground wire or water pipe: troubleshooting for electricians · 2023 NEC ·
Current on the ground wire or water pipe
Use a clamp meter to find whether it’s coming from inside the building or from the utility side.
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How it works
Grounding and bonding conductors shouldn’t carry current in normal operation. Current there means neutral current has found a second path: a neutral-to-ground connection past the service, a metal water line shared with the neighbors, or a weak service neutral. That “objectionable current” causes tingles at plumbing, interference and heat, and it is a warning sign about the neutral.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- Where are you reading the current?
- Grounding electrode conductor or water pipe at the serviceTest: Clamp it with the main on, then offExpect: Little or no current with the main on or off.
- Current stays with the main offWith the main back on, do lights dim and brighten, or does voltage shift as big loads start?
- Yes, voltage shifts with loadA failing service neutral
- No, voltage is steadyNeighborhood neutral current on the water pipe
- Current drops to near zero with the main offTest: Clamp each circuit’s hots and neutral togetherExpect: Near 0 A on every circuit. Current that goes out on the hot comes back on the neutral.
- One branch circuit shows net currentTest: Look for a neutral-to-ground connectionExpect: OL (open). Loads left plugged in may show a high reading.
- Low ohms or continuityNeutral touching ground on this circuit
- OL or very highA load is leaking current to ground
- A subpanel feeder shows net currentNeutral bonded at or past a subpanel
- Every circuit reads near 0 AThe building’s own neutral current returning through the pipe
- One branch circuit shows net currentTest: Look for a neutral-to-ground connectionExpect: OL (open). Loads left plugged in may show a high reading.
- Current stays with the main offWith the main back on, do lights dim and brighten, or does voltage shift as big loads start?
- A ground wire or conduit on a feeder or branch circuitTest: Compare the circuit conductors and the groundExpect: Both near 0 A.
- Net current, and current on the groundTest: Look for a neutral-to-ground connectionExpect: OL (open). Loads left plugged in may show a high reading.
- Low ohms or continuityNeutral touching ground on this circuit
- OL or very highA load is leaking current to ground
- Net near zero, but current on the ground or conduitCurrent from another circuit or path
- A few milliamps onlyNormal leakage
- Net current, and current on the groundTest: Look for a neutral-to-ground connectionExpect: OL (open). Loads left plugged in may show a high reading.
- Grounding electrode conductor or water pipe at the serviceTest: Clamp it with the main on, then offExpect: Little or no current with the main on or off.