Okay, this is a critical question for safety and code compliance. Here's the breakdown of the requirements and why having the bonding grid behind the gypsum board is likely a problem, and what you should do

Understanding Pool Bonding Requirements (NEC 680):
Purpose

The primary purpose of pool bonding is to create an equipotential plane. This means reducing voltage gradients in and around the pool area. If a fault occurs (e.g., a pump motor short-circuits), the voltage potential between different points in the pool area will be minimized. This significantly reduces the risk of electric shock to anyone in or near the pool.

Key Components of the Bonding Grid

A continuous, unbroken conductor encircling the pool (usually #8 AWG copper). Connections to all metal parts within a specific distance of the pool (lighting fixtures, ladders, handrails, etc.). Connections to metal parts of the pool structure (rebar, pool shell). Connections to all electrical equipment associated with the pool (pumps, heaters, lights).

Why Direct Contact is Crucial

The NEC requires intimate contact with the items being bonded. The bonding conductor needs to be directly bonded to the metal or conductive surface it is intended to bond. This provides a low-impedance path for fault currents to flow back to the electrical source, tripping the breaker quickly and safely.

Why Your Current Installation is Problematic


Gypsum Board is an Insulator

Gypsum board (drywall) is an insulator. It does not conduct electricity well. Marble is also an insulator.2.

Impedance

Placing the bonding grid behind the gypsum board means the fault current would have to travel through the gypsum board, then through the mortar, and finally through the marble to reach a person in the pool. This significantly increases the impedance (resistance to current flow) and defeats the purpose of creating an equipotential plane.3.

NEC Violations

It's highly likely that this installation violates NEC 680.26, which covers bonding of metallic parts. The NEC generally requires direct bonding to the items being bonded.

What You MUST Do


Relocate the Bonding Grid

The bonding grid

must be installed in front of the gypsum board. It needs to be directly bonded to any metal parts in or around the pool area that are within reach or could become energized.2. Metal Structure Concerns

If the gypsum board is mounted to metal studs, you must bond the metal studs themselves to the bonding grid.3.

Marble Installation Details

How the marble is installed is critical. If the mortar used contains metal (some mortars do), you might be able to bond to the mortar if* that mortar is in direct contact with metal parts of the pool structure. However, this is a very risky proposition and would require significant testing to verify its effectiveness. I would strongly recommend not relying on mortar as a means of bonding.4.

Consider a Metallic Mesh or Grid

Some installers embed a metallic mesh or grid into the mortar bed that holds the marble. This mesh is then directly bonded to the main bonding grid. This can help ensure equipotentiality at the surface of the finished wall.5.

Direct Bonding to Pool Structure

If possible, run bonding conductors directly to the metal parts of the pool structure that are behind the wall. This is the most reliable approach.6.

Consult with an Electrical Inspector

Before proceeding, consult with your local electrical inspector. They will have the final say on what is acceptable in your jurisdiction and can provide specific guidance.7.

Document Everything

Document the bonding process with photos and detailed descriptions. This will be essential for inspections and future reference.8.

Cold Plunge

Dont forget that the cold plunge also needs the same bonding requirements as the pool.

In Summary:

The current installation with the bonding grid behind the gypsum board is almost certainly not compliant with the NEC and creates a significant safety hazard. Relocate the bonding grid to the front of the gypsum board to ensure direct bonding to any metal parts, or to a metallic mesh embedded in the mortar. Consult with your electrical inspector for specific guidance and approval. Prioritize safety and compliance! Flag for review