Mike Dolt Enterprises
Mike Dolt Enterprises
User: jlauck, Location: North Carolina
Asked on: Monday, July 14, 2025 at 3:52 pm EDT
Answered on: Monday, July 14, 2025 at 3:58 pm EDT
Question: I have an inground fiberglass swimming pool in my backyard. Recently I noticed a tingling sensation at one corner of the pool when touching the pool water with bare wet feet from the concrete pool deck. The location where this happened is also nearest the corner where the plumbing and electrical enter the pool deck area from the remote equipment pad up near my home's foundation. There is a retaining wall that the plumbing and electrical dives down behind before running under the pool deck. Upon investigation I found that the entire length of bare copper conductor between the pool and equipment pad has corroded away in the ground, AND the ground has a steep voltage gradient with a peak of about 40 volts right around the retaining wall.It seems the bonding conductor suffered accelerated electrolytic corrosion due to the ~40 volts in the earth around it. The local electric utility has been out multiple times to "investigate" this elevated stray voltage as it is present even when my home's main breaker is off (but not when power is out to the entire neighborhood). It is obvious that the bonding grid for the pool must be repaired, but I am concerned that the steep gradient so close to the edge of the pool deck still presents a safety hazard. Although not required by the NEC, I could extend the bonding grid out to the retaining wall but then I would be importing that ~40V to the entire grid which seems like it could potentially create other problems down the road.Like most or all of the U.S. I'm on a multi-grounded utility neutral, and although no neutral integrity issue has been found with my home's service, it seems there could be an issue with my neighbors or possibly the primary utility conductors at the street. Has anyone experienced this level of voltage gradient in the soil before without a fault someplace? Should I just hang up the hat with the utility company and simply repair the pool bonding grid, routing the conductor from the pool area to the equipment pad away from the area of the elevated voltage?
This is a serious and complex situation. You're right to be concerned about safety. Here's a breakdown of the issues and potential solutions, along with considerations
Understanding the Problem
Stray Voltage
A 40V ground potential difference is significant. This isn't normal and presents a shock hazard.
Electrolytic Corrosion
The stray voltage caused the accelerated corrosion of your bonding conductor. This is a telltale sign that the voltage is continuously present.
Source of Voltage
The fact that the voltage is present even when your main breaker is off but disappears when the entire neighborhood's power is off points to a source outside your home, likely utility-related or a neighbor's problem back-feeding through the ground.
Ground Voltage Gradient
This is the change in voltage potential as you move across the ground. A steep gradient, like you describe, concentrates the risk. A person standing with one foot on the concrete deck (assumed to be near zero volts) and the other foot in the water with (potentially) 40 volts relative to ground can experience a shock as the voltage will flow through them.
Why is this so dangerous? Cardiac Arrest
Even relatively low AC voltages (think in the 20-30 volt range) can cause cardiac arrest, especially in wet environments. The tingling sensation is a clear warning sign.
Children and Pets
They are particularly vulnerable to electric shock.
Bonding Grid Failure
If the pool's bonding grid is no longer continuous due to corrosion, the potential for voltage differences within the pool area increases drastically, exacerbating the hazard.
Your Options and Considerations
Persistence with the Utility
Do not give up! This is a high-priority safety issue that the utility must address. Escalate your concerns. Document everything, including dates, times, names of people you spoke with, and what actions (if any) they took. Mention the specific voltage gradient you've measured, the corrosion of the bonding conductor, and the shock you experienced. Emphasize the safety hazard and potential liability. Ask Specific Questions
Demand to know what steps they've taken to isolate the source of the stray voltage. Have they checked the primary neutral? Are they aware of similar issues in your area? Have they checked your neighbors' grounding?
Request a Qualified Technician
Ensure the person investigating has experience in stray voltage issues.
Consider a Formal Complaint
If the utility is unresponsive, file a formal complaint with your state's public utility commission (PUC).2.
Pool Bonding Grid Repair
This is essential. Replace the Bonding Conductor
Use a solid, insulated copper conductor (e.g., #8 AWG or larger). Make sure to bond all metal parts of the pool (pump housing, ladder anchors, etc.). Use proper bonding lugs and ensure they're clean and tight.
Route the Conductor Away from the Voltage Gradient
As you suggested, avoid routing the new bonding conductor through the area of high voltage gradient near the retaining wall. Consider a different route that stays as far away from that area as practical.
Consider a Grounding Electrode at the Pool
Drive a ground rod near the pool equipment (as close as is practical) and bond it to the bonding grid. This will provide an additional grounding point. This should NOT be considered a replacement for a properly installed/repaired main bonding conductor.3.
Addressing the Voltage Gradient (The Tricky Part)
Extending the Bonding Grid
You're right to be cautious about extending the bonding grid to the retaining wall. While it could equalize the potential, it could also introduce the stray voltage to the entire pool area, potentially creating a larger hazard. Don't do this without professional guidance.
Mitigation Techniques (Professional Consultation Needed)
Here are some mitigation techniques that require professional evaluation and design. This is NOT a DIY project.
Equipotential Plane
This is a grid of closely spaced conductors embedded in the concrete around the pool, bonded to the pool bonding grid. It helps to create a more uniform voltage potential across the surface around the pool, reducing the voltage gradient. The spacing of the conductors and their connection to the grid is critical and needs to be engineered.
Isolation Techniques
Could you effectively isolate the concrete decking? Probably not feasible.
Soil Treatment
Certain soil treatments can reduce its conductivity, which can lessen the voltage gradient. Again, this needs professional evaluation.
Neutralizing Mat
Install a neutralizing mat, either in the water or on the deck near the step-in location. This will provide a "zero-voltage" location for someone to enter the water.4.
Professional Consultation
Licensed Electrician
Hire a licensed electrician experienced in pool bonding and grounding, as well as troubleshooting stray voltage issues. Make sure they are well-versed in the latest NEC requirements (specifically Article 680).
Electrical Engineer (Optional)
In a complex situation like this, consulting an electrical engineer with expertise in grounding and bonding, and especially in stray voltage mitigation, might be warranted. They can perform detailed measurements, model the electrical system, and design an effective solution.5.
Temporary Safety Measures
Restrict Pool Use
Until the problem is resolved, restrict or prohibit pool use.
Warning Signs
Post clear warning signs about the potential shock hazard.
Rubber Mats
Place thick rubber mats around the pool deck, especially near the area where you felt the tingling. This will add some degree of insulation.
Insulated Footwear
Require anyone near the pool to wear rubber-soled shoes or sandals.
Important Considerations
NEC Compliance
Ensure that all work is done in compliance with the latest National Electrical Code (NEC), specifically Article 680 (Swimming Pools, Fountains, and Similar Installations). Local codes may have additional requirements.
Permitting and Inspections
Obtain the necessary permits and have the work inspected by a qualified electrical inspector.
Documentation
Keep detailed records of all measurements, repairs, and communications with the utility.
Insurance
Notify your homeowner's insurance company about the situation.
In summary
You have a serious problem that requires a multi-faceted approach. Don't try to fix it yourself. Persistence with the utility, professional electrical assistance, and strict adherence to safety measures are essential.
Disclaimer:* I am an AI chatbot and cannot provide professional electrical advice. This information is for general guidance only. Always consult with qualified professionals for specific recommendations and solutions. Flag for review