Okay, this is a complex and potentially dangerous situation. You've done a lot of good troubleshooting, but let's break this down and focus on safety and Code compliance

Key Concerns & Dangers:
Stray Voltage

The voltage readings you're getting between the pool light shell/ladder and the water are a serious shock hazard. Even low voltage can be dangerous, especially in water. The tingling the client is experiencing is a warning sign.

Equipotential Bonding System Failure

It seems the original equipotential bonding system is either degraded, incomplete, or compromised. This is the most likely source of your problems.

Underground Fault

The fact that you're getting voltage even with the main disconnect off is extremely concerning. This points to an external source of stray voltage from the utility grid or a neighboring property.

Analyzing Your Troubleshooting


Voltage Disappearance When Disconnected

As you indicated this is likely NOT a problem on the load side as you still have voltage after disconnecting ground, neutral and power.2.

GFCI Protection of the Pump

While good, GFCI protection on the pump won't address stray voltage issues within the pool itself. GFCIs protect against ground faults in the pump motor and wiring, not voltage gradients in the water.3.

Dedicated Bonding Conductor to Light

Good effort to isolate the light and provide a direct bond. The fact that it didn't change the voltage reading is telling.4.

Utility Disconnect Effect

That is strange. The utility disconnect cutting power should eliminate the load side of your electrical as a cause.

Next Steps - Prioritized for Safety


IMMEDIATE WARNING

Tell the client

in writing that the pool is a potential shock hazard and should NOT BE USED until the problem is resolved. This is critical for liability protection.2. Utility Notification

Contact the utility company immediately. Report the stray voltage and that you've traced it to the grounding system. They have specialized equipment and expertise to identify and correct external stray voltage problems on the power grid. They also have specialized people who test for stray voltage around livestock.3.

Re-inspect Bonding Connections

With power OFF, carefully examine

all bonding connections around the pool, pool equipment, and pool structure. Look for corrosion, loose connections, broken wires, or anything that might interrupt the bond. Check the connection to the rebar (if applicable) using an earth ground tester (not just a continuity tester). Verify the integrity of the bond wire itself. It may be corroded underground. Carefully inspect the brass conduit of the light niche in the pool shell. They are known to fail over time and become porous.4. Comprehensive Bonding Upgrade

Regardless of what you find above, strongly recommend a complete bonding system upgrade to meet current NEC standards. This typically involves: A solid #8 AWG copper bonding grid encompassing all metallic parts within 5 feet of the pool. This includes: Pool rebar (if present) Metal pool light niche/housing Metal ladder Metal handrails Metal diving board supports Pump motor housing Any other metallic objects within 5 feet All connections must be made using listed bonding connectors.5.

Water Bonding Is a Myth (for compliance)

There is no such thing as bonding the water in a pool. There is no Code requirement for a metal rod to be suspended in the water.6.

Do NOT Install a Ground Rod in the Pool Water

This is extremely dangerous and a violation of the NEC. You would essentially be creating a pathway for fault current to flow directly into the water.7.

Testing After Repair

Once the bonding system is upgraded, and the utility has addressed the stray voltage, you

must perform thorough testing to ensure the problem is resolved: Voltage Measurement

Measure the voltage between the pool water and any metal part of the pool equipment, ladder, or surrounding grounded objects. Ideally, this should be very close to zero.

Continuity Testing

Verify continuity between all bonded parts.

Ground Fault Testing

With the pool equipment running, use a clamp-on ammeter to check for excessive current on the bonding conductor. This could indicate a ground fault.

Have a Professional Test

Have the utility company check for stray voltage.

Important Considerations



NEC 680

Familiarize yourself with Article 680 of the National Electrical Code, which covers swimming pools and spas.

Local Codes

Check with your local building department for any specific requirements.

Liability

Document everything you do, including your warnings to the client, your troubleshooting steps, and the results of your testing. Consider having a qualified electrical engineer review your work.

The Mike Holt Quote & Your Interpretation

Your interpretation of Mike Holt's statements is correct. Here's why it's crucial:

Bonding Creates Equipotential

The purpose of equipotential bonding is to create a zone where all metallic parts are at the same electrical potential. This minimizes the risk of shock if someone touches two different metal parts simultaneously.*

Compromised Bonding = Voltage Gradients

If the bonding is incomplete or compromised, voltage gradients can develop in the pool area. This means that the voltage between two points in the water or between the water and a metal object can be significantly different.

In Conclusion:

This is a serious situation requiring immediate action. Safety is paramount. Don't take shortcuts, and don't hesitate to seek help from qualified professionals. The client may need to rip up the deck to replace the copper bonding wire, especially if it is a wire grid encompassing the entire perimeter. The utility company MUST investigate the stray voltage problem. Flag for review