Equipotential bonding for pools
Permanently installed pools need equipotential bonding whether or not they have electrical equipment. It ties the shell, the water, nearby metal and the deck or ground within 3 ft of the pool together to reduce voltage differences where people walk and swim.
What the code requires
For permanently installed pools, bonding connects the pool shell, the water, nearby metal parts and the surrounding surface to reduce voltage differences between them. It is required whether or not the pool has electrical equipment. The perimeter surface extends 3 ft horizontally beyond the inside walls, covering surfaces from 3 ft above to 2 ft below the maximum water level, paved or not. A permanent wall or building 5 ft or taller limits bonding to the pool side.
Perimeter bonding attaches to a conductive shell's reinforcing steel or copper grid at a minimum of 4 uniformly spaced points. With a nonconductive shell, it goes to the 8 AWG copper bonding conductor and any conductive support structure. Fixed metal parts within 5 ft horizontally of the inside walls and no more than 12 ft above the maximum water level are bonded. So are metal parts of electric pool covers, of pool water circulation, treatment, heating, cooling and dehumidification equipment, and of other electrical equipment within those same distances. If no bonded part touches the water, the water needs at least 9 sq in. (5,800 mm²) of bonded, corrosion-resistant conductive surface in contact with it.
Under paving, the code calls for fully embedded rebar or welded wire reinforcement. If that isn't possible, welded wire or a copper grid goes no more than 6 in. below finished grade: 8 AWG solid bare copper, or steel of at least 6x6-W2.0xW2.0 mesh or #3 rebar on a 12-in. grid, extending at least 3 ft out, with only listed connectors or exothermic welds.
In unpaved areas, a single bare solid 8 AWG copper ring is allowed only where swimmers have no direct access. It sits 18 to 24 in. from the inside walls and 4 to 6 in. below finished grade. Elsewhere, a grid 4 to 6 in. below finished grade is required. Since January 1, 2025, copper grid and steel wire that is not fully embedded must be listed.
On the job
- Where swimmers can step out onto soil or lawn, a single copper ring is not allowed. A grid or mesh is required.
- Grid products installed on or after January 1, 2025 must be listed for corrosion resistance and mechanical performance.
- Depths are measured from finished grade, not subgrade.
- Inspectors look for the 4-point tie-in to a conductive shell and, where no bonded part touches the water, the pool water bond.
Exceptions that matter
- Under TIA 23-9, nonconductive perimeter surfaces separated from the earth, or raised on nonconductive supports, need no perimeter bonding.
- Metal parts separated from the pool by a permanent barrier that prevents contact by a person do not need bonding.
- Metal parts of listed double-insulated equipment are not bonded. Where a double-insulated pump motor is used, a solid 8 AWG copper conductor must still run from the bonding system to an accessible point near the motor, ready for a replacement motor.
What changed in 2023
The 2023 edition stated that bonding applies whether or not the pool has electrical equipment and added water treatment, heating, cooling and dehumidification equipment to the bonded parts. TIA 23-9, issued March 21, 2023 and effective April 10, 2023, rewrote the perimeter rules (height band, depth from finished grade, listed grids, limits on the single ring). The printed text without the TIA measures ring and grid depth below the subgrade and allows the ring anywhere; California may print the code without it, so confirm with your building department.
Related sections
- NEC 680.7
- NEC 680.14
- NEC 680.42(B)
- NEC 680.43
- NEC 250.8
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CSLB #354550 · C-10 Electrical · Licensed since 1978 · $25,000 contractor's bond