Study Compares Equipotential Bonding Methods

The Florida Swimming Pool Association’s research and education nonprofit has conducted a study that it says supports the allowance of a single #8 AWG copper wire loop as an option for the equipotential bonding of pools and spas.

The Pool Industry Council (PIC), an independently run group, studied nine recently built pools to compare the performance of the wires and copper bonding grids. The motivation came from the long-standing debate over whether the National Electrical Code (NEC) should include the wires — the most-common method — as an option or require copper or steel grids on every pool. Over the past couple decades, the NEC, upon which many state and municipal codes are based, has gone back and forth on the issue. Once again, the National Fire Protection Association, which writes the NEC, seems poised to remove the wire option, having published a Tentative Interim Amendment (TIA) saying grids only should be used. While not officially part of the code, TIAs often become adopted at the next code-revision cycle.

“The Pool Industry Council thought it was worth everybody’s time and investment to get a complete in-field study of the issue, establish an objective threshold for what bonding is supposed to accomplish, and see how the methods stack up to an objective standard,” said Dallas Thiesen, FSPA’s chief government relations officer.

PIC commissioned SunSmart Engineering to perform the study on perimeter bonding, meaning bonding in the area within 3 feet of the water’s edge. Over the course of nine and a half weeks, the company looked at nine residential pools in Central Florida. Among the pools were three concrete models with the grid and three concrete pools with the wire. Also studies was a fiberglass pool outfitted with a stainless steel plate in the skimmer and a wire (since it has no rebar, making it non-conductive). They were built by three different contractors, all complying with the 2023 NEC.

“This sort of test method, [done] in the wild to real-world pools, was never done before,” said John Antonelli, vice president of engineering for SunSmart Engineering, based in Lake Mary, Fla. “A lot of the research into the subject was either done at a single pool that may or may not have had incidence of shock, or in a lab …”

The researchers concluded that, while the grids performed slightly better than the wire, both fell well within the performance parameters for human safety.

“The bottom line is that both methods of perimeter bonding tested … work to effectively mitigate equipotential voltage issues and can confidently be used to bond swimming pools and spas when installed properly,” Antonelli said.

The Pool & Hot Tub Alliance contributed technical guidance and funding for the study.