In our April 1 edition of Service Industry News, we published an article titled “Florida Pool Industry Pushes Back Against NEC’s Equipotential Bonding Grid Mandate.” The article reported on the Florida Swimming Pool Association’s (FSPA) opposition to a recently issued Tentative Interim Amendment (TIA) to the 2023 National Electrical Code (NEC), which mandates the use of a three-foot-wide equipotential bonding grid around swimming pools.
The article generated important feedback from industry experts, including Reuben Clark, a longtime electrical safety advocate and regular contributor to this publication. Clark has been involved in equipotential bonding and stray voltage mitigation for more than 20 years and raised several critical points to clarify the technical and safety implications of the NEC’s updated requirements and the FSPA’s opposition to them.
Among the most significant points Clark raised:
• Photo Clarification: The image published with the article was captioned as an example of an installation using a single 8 AWG copper conductor. However, it actually depicted an equipotential bonding grid using copper wire, as described by electrical code expert Mike Holt. This mislabeling was an editorial oversight, and we thank Clark for the correction.
• Code History: The article stated that the bonding grid requirement originated 17 years ago. In fact, the grid mandate first appeared in the 2005 version of the NEC — 20 years ago.
• Incident Record: Our article quoted FSPA’s position that the single- wire method has been used in Florida for 17 years “without incident.” Clark disputes this, citing 13 fatalities in Florida that he says were attributable to inadequate equipotential bonding during that time period. While pool builders may not always be made aware of these incidents — which are often first reported to utility companies — they illustrate the potential risks of insufficient bonding practices.
• NEC Bonding Options: FSPA described the NEC’s bonding grid as a costly copper-only solution. In reality, the NEC allows three compliant methods for creating the equipotential bonding grid: (1) #3 or larger rebar tied in a 12-inch grid pattern and fully encapsulated in concrete, (2) W2.0 x W2.0 wire mesh, or (3) a copper conductor grid such as those manufactured by certain suppliers. In many cases, the copper grid is actually the most cost-effective of the three.
• Cost Implications: While FSPA cited rising costs as a central concern, Clark notes that the incremental cost difference between a copper bonding grid and a single wire is typically $300–$500 — a relatively small amount in the context of a new pool build. He further argues that many builders are already choosing to install high-end automation and lighting systems, which far exceed this cost.
• Supporting Studies: FSPA’s claim that only one fiberglass pool study was used to justify the NEC change was also disputed. According to Clark, extensive testing has been conducted over several code cycles by utility representatives, independent engineers, and safety researchers. These studies culminated in a unanimous recommendation by a specially appointed NEC Task Group, which led to the approval of the TIA, deeming the bonding change both urgent and necessary.
As a publication, Service Industry News aims to reflect the range of voices in our field — including the regulatory bodies, professional associations, manufacturers, and builders that shape our industry. The original article reported on FSPA’s advocacy efforts and concerns, not as an endorsement of one method over another, but to inform our readers of ongoing developments that may affect their businesses.
That said, we deeply value technical accuracy and have a responsibility to keep our readers well-informed on matters of public safety. We appreciate the feedback and expert insight Clark provided, and we look forward to continuing this important conversation. An accompanying article by Electric Power Research Institute (EPRI) will further explore the technical reasoning and further background on the data behind the NEC’s bonding updates.
As always, safety remains paramount. We thank our readers for their engagement and for holding all of us accountable to the highest standards.
— Service Industry News NEC TIA 23-9 Making Swimming Pools Safer By Doug Dorr, Technical Executive, Electric Power Research Institute (EPRI)
The U.S. Coast Guard-funded Electric Shock Drowning report contains a summary of 15 swimming pool incidents that when combined have resulted in 12 fatalities and another 23 serious shock injuries. The table below breaks down the 15 swimming pool incidents into their reported causes to include faulty underwater lighting, faulty pool pumps, and assorted wiring errors. To add to this list of shock concerns, the author has participated in hundreds of additional swimming pool and splash pad electric shock investigations and has observed several additional causes for the incidents including malfunctioning ground fault circuit interrupters, faulted water heaters, and even a mis-wired hot dog cart at a community swimming pool.
Every one of the shock concerns described has a common thread, whereby in each scenario, the water becomes inadvertently electrified and the surrounding walking and sitting surfaces create a convenient earth return path for electric currents when a human body bridges the gap between them. For example, when a swimmer is immersed up to their chest in the electrified water and their hands and forearms are stretched out onto the pool deck, the electric current flows from the water, through the chest area, and then out the forearms and hands, then into the deck surface, and back to the source of the electricity. This means that when one of the described incidents happens, not only are the victims in danger, but the rescuers and first responders can also get electrocuted when “bridging the gap” by simultaneously contacting the pool deck and the water.
Considering that sticking or malfunctioning GFCI’s have been the culprit in several of the shock investigations, there are three alternative ways to either eliminate, avoid, or reduce the severity of this problem. These three options include a) electrical isolation, b) blocking the current return path, and c) creating an electric equipotential safe zone.
Electrical Isolation — This approach is by far the most effective but also happens to be the least practical. In this approach, we simply would not allow the possibility of the water becoming electrified under any circumstances. To do so, we would not be able to use any underwater lighting with green wire grounds; we would not be able to use any metallic ladders or handrails around the water; and we would not be able to physically bond or interconnect the bonding conductors for the circulation equipment to the bonding conductor that connects to the water and to other bonded parts in the pool area. Each of these non-allowances are violations of the National Electric Code, and therefore, we will assume that electrical isolation is not feasible unless significant code exceptions and detailed prescriptive direction is provided in future versions of the code.
Blocking the current return path — This approach has been used in some ultra-low voltage nuisance shock and perception cases. The approach involves coating the deck with a rubber or insulating material with sufficient thickness to make the pool deck non-conducting to avoid any current flowing through the deck and back to the source of the electricity. While this approach can resolve any electrified water to deck shock concerns, the coatings are not always aesthetically suitable to the pool owner and there are no easy or standardized methods to certify that the coating thickness is suitable for both low level stray voltages and for full line faults.
Creating an electric equipotential safe zone — This approach is the foundation for NEC Article 680.26 and if implemented correctly can keep pool users safe during every one of the previously described scenarios where the water could become inadvertently energized. To understand the “equipotential safe zone” concept, it is important to understand that we are not eliminating or blocking the inadvertent voltages, and we are not removing the problem sources.
Instead, our objective here is to “float” everything that is electrically conductive up and down at exactly the same potential as compared to the voltages on the pool water. When a human bridges the gap between two surfaces at the same electric potential, nothing happens, and no perceptible currents will flow through the body.
The solid bare Number 8 copper bonding wire does a good job of interconnecting and electrically bonding the metal parts like the ladders, handrails, underwater niche retaining rings, but it can’t help us with achieving equipotential across the walking and sitting areas around the pool deck. In fact, you cannot electrically bond pavers, you cannot electrically bond concrete, and you cannot electrically bond dirt!
The only way to achieve the Article 680.26 required “equipotential safe zone” is by installing a gridded mesh either immediately beneath the decking material or by embedding the mesh within a poured deck material and then using the bonding electrode to interconnect the gridded mesh to the water and to all the other metal parts in the pool area.
Why is NEC 680.26 TIA 23-9 Essential?
The NEC is always evolving and always striving to make the use of electricity as safe as possible for buildings and structures within its areas of jurisdictional focus. Toward this objective it became apparent over the past two decades that fatalities and injuries like those cited in the Coast Guard report continue to happen over and over, and modifications to NEC Article 680.26 were deemed imperative when in 2022 the NFPA Standards Board directed a balanced committee of experts to convene and to develop a new minimum design criteria for swimming pool equipotential surfaces. Simply stated, between the deaths documented in the Coast Guard report and the decades of testing on equipotential zones around swimming pools, there was consistent evidence that showed that a single bare copper bonding conductor buried four to six inches beneath the subgrade around a swimming pool was inadequate and could not bring the surface of the pool deck to that same voltage potential as the pool water. Clearly a more comprehensive approach along with modifications to NEC 680.26 were necessary.
EPRI Field Tests:
To obtain some objective and comparative test results, the Electric Power Research Institute (EPRI) conducted more than two years of tests on virtually every equipotential concept available including the use of grounding techniques, chemical ground enhancements, bonding rings, and copper and steel gridded meshes. A key focus of the testing was to compare the different configurations during actual fault scenarios where the pool water was electrified, and a human body path could be simulated to measure the currents that would flow between the water, through a human, and into the surrounding deck surfaces.
Bonding and Grounding Ring Results: Testing performed by (EPRI) included #8 bare copper rings buried at different burial depths and placed at different distances away from the pool walls. There were also tests performed with dozens of ground rods connected to those bonding rings. It was clear that even when bonded solidly to the water, these ring configurations simply didn’t have the ability to create an equipotential safe zone on the pool deck walking and sitting surfaces, and it became apparent that electric shock fatalities and injuries would continue until the NEC made meaningful modifications to Article 680.26.
Equipotential Grid Results:
The next set of tests are founded in research from electric power substation step-and-touch potentials and corresponding research at dairy farms with equipotential planes and gradient ramps. The simple concept is that if you want the surface above an energized system to have equal voltage across all the walking or standing surfaces of interest, you must use a conductive mesh of gridded squares or rectangles beneath the full area of interest. Three important takeaways for the Gridded Mesh tests were:
• Using the gridded squares instead of rectangles provided the best equipotential performance and required the least amount of total feet of wire for fabrication of the grid.
• Getting the grid as close to the pool deck surface as possible provided the best equipotential performance, and burying the conductive wires four to six inches beneath the subgrade was inadvisable.
• Using smaller squares makes it more difficult for a person to get their arms and feet into spots where they aren’t partially on top of the wire and extending the grid, out further from the water is a useful way to eliminate concerns where a person (holding an aluminum pole on a skimmer) could get shocked if they were standing on the deck beyond the equipotential zone.
• The improvement measured for the grid as compared to the single bare wire was dramatic, where a faulted underwater light yielded equivalent chest current measurements of 80 to 100 milliamps for the single wire and only three to five milliamps for the gridded mesh. This is the difference between an electrocution and a nuisance perceptible shock incident!
These results are consistent and repeatable, and EPRI opens the testing to any electrical inspectors or NEC Code Panel members during their annual summer training seminars. In fact, five of the subject matter experts that worked on the revised criteria found in NEC TIA 23-9 have attended and conducted their own measurements during the pool testing.
Key Takeaways
The good news for pool owners and users is that TIA 23-9 finally provides a way to avoid unnecessary fatalities and injuries to our children and to our loved ones, even when things go wrong, electrically speaking. Many such incidents have been documented in the Coast Guard report, and as time goes on, we can expect a dramatic reduction in the number of fatalities and injuries once TIA 23-9 is mandatory across the U.S.
The bad news is that even though the NFPA Standards Council ordered the inclusion of TIA 23-9 in the 2023 NEC (under an Emergency Nature provision) there remain many legacy pools that aren’t compliant with this minimum safety requirement. Those responsible for installation and for enforcement of the NEC criteria should note that these new requirements provide a minimum level of safety, and any attempt to lessen that safety by not following TIA 23-9 requirements could be considered grossly negligent.
The beauty and the simplicity of TIA 23-9 is that we no longer must worry about the type of pool construction, or about GFCI malfunctions, or questionable grounding, or even the different ways electrocutions and shock injuries can happen. TIA 23-9 provides a way to ensure that every properly bonded component and surface (including the water and the deck) will float up and down together with whatever voltage happens to be present poolside.
About the Author: Doug Dorr ddorr@epri.com is a Technical Executive at the Electric Power Research Institute. Over a thirty-year career with EPRI Doug has led many Public Safety related research initiatives and has a broad background in testing, measurement, data acquisition, and field investigations resulting in three related U.S. Patents. Doug currently manages EPRI’s public safety and electric shock concerns R& D activities. He has developed course material for understanding human and animal bioelectricity and teaches hands-on workshops for stray voltage evaluations at swimming pools, marinas, urban areas, dairy farms, and for electric power distribution systems. Doug also developed and maintains all content available at https://strayvoltage.epri.com and is a lead content developer for the IEEE 1695-2024 Guide to Understanding, Diagnosing, and Mitigating Stray and Contact Voltage. He has conducted over 100 field investigations for challenging voltage shock, perception, and electrocution incidents and has contributed to several additional IEEE, NEC, CSA, IEC and CIGRE standards publications. Doug has a Bachelor of Science degree in Engineering from Indiana Institute of Technology.
