WiremanWireman · Stray voltage in pools, showers or barns: troubleshooting for electricians · 2023 NEC ·
Stray voltage in pools, showers or barns
Tingles in water or at livestock waterers: measure it, find out whether it comes from the property or the utility, and fix the bonding.
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How it works
Stray voltage is a small voltage between two things a person or animal touches at the same time: pool water and the deck, a shower valve and the drain, a waterer and the barn floor. It usually comes from neutral current flowing through the earth and the grounding system, from the utility’s grounded neutral or from a problem on the property. Wet skin makes small voltages feel strong, and livestock react to levels people can’t feel. Equipotential bonding fixes the effect by keeping everything within reach at the same voltage.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- Clear people and animals out of the water or area before you test. Where is it happening?
- Pool, spa or hot tubTest: Measure water to bonded metalExpect: Near 0 V everywhere. A voltage people can feel is too much.
- Voltage presentTest: Turn things off and measure againExpect: The reading drops to near 0 V at one of these steps, or doesn’t.
- Gone with the pool equipment offFault in pool equipment
- Gone only with the main offSource on the property
- Still there with the main offVoltage from the utility side
- Near 0 VNot present right now
- Voltage presentTest: Turn things off and measure againExpect: The reading drops to near 0 V at one of these steps, or doesn’t.
- Shower or tubDoes it happen only when the water heater (or another appliance) is running?
- Only when the water heater is heatingWater heater leaking to the water
- All the timeTest: Measure the pipe to the equipment groundExpect: Near 0 V.
- Voltage between pipe and groundWater pipe not bonded
- Near 0 VWhole grounding system raised
- Barn, dairy or livestock watererTest: Measure contact voltage at the animalExpect: As close to 0 V as possible. Livestock can react to levels around a volt or less, well below what people notice.
- Still there with the farm main offVoltage from the utility side
- Drops with the main offTurn the farm’s circuits back on one at a time. What raises the voltage?
- One piece of equipmentOne farm load leaking current
- It rises with total loadSource on the property
- Near 0 V even with loads runningNot present right now
- Pool, spa or hot tubTest: Measure water to bonded metalExpect: Near 0 V everywhere. A voltage people can feel is too much.