By Reuben Clark
Equipotential bonding is simply bringing all conductive objects to “equal potential voltage.” This is achieved by electrically bonding/ connecting the conductive objects. In the case of a swimming pool and deck — the rebar reinforcement of a concrete pool shell, the rebar or copper grid in the deck, and any handrails, ladders, or other metal objects — are typically connected with a #8 solid bare copper wire, then run back to the pool pump. This connects the conductive objects/area of the pool system, which brings everything to the same potential voltage.
A concrete pool shell is typically reinforced for strength by creating a grid of 3/8” rebar over which the concrete is poured. This grid creates an equipotential plane around the body of water. The 2023 National Electrical Code also requires a similar grid of rebar, structural steel grid, or copper grid to be installed in the pool deck. These planes protect the swimmer in the pool and on the deck from stray and contact voltage that may be present in the ground.
A shock, however small, is the presence of voltage differences. As the voltage differences get larger, so does the danger. The amount of voltage that can be present on a pool deck or in a pool or spa could cause serious harm and even fatalities. The voltage can come from a number of sources. Most often, it comes from older, damaged, or poorly installed electrical systems.
Is there a code requirement for equipotential bonding of pools?
YES! Since 2005, the National Electrical Code has required the shell and deck of the pool to contain an equipotential grid, but in 2008 the requirement was removed from the deck. This left the utility industry to try to correct problems created by inadequate pool building. The utility industry has been trying ever since to bring back the proper level of safety, and in 2023 achieved success. After a contentious debate during the 2023 code development process, a handful of people was just enough to attempt delaying the requirement until 2026. However, after utility industry, laboratory, and subjectmatter experts presented the proven science, the data from numerous events in the field, and the 2022 US Coast Guard Report of fatalities, the NFPA Standards Council acted to implement TIA 1687 immediately.
As of March 2023, through D#23-1, the 2023 NEC now has a restructured article 680.26, covering the bonding of swimming pools and decks.
There are three ways builders can create the equipotential plane in the first 3 feet of perimeter surface surrounding the pool shell.
1. Minimum Number 3 rebar tied in 12” x 12” squares, chaired up to be completely embedded in concrete. Poured concrete decks can be constructed with this method.
2. 6×6-W2.0 x W2.0 steel mesh, chaired up to be completely embedded in concrete. Poured concrete decks can be constructed with this method.
3. Copper Grid from #8 Solid AWG Wire welded in 12” squares. This does not have to be chaired up and embedded in concrete: It can lay on or in the dirt or concrete. All decks can be constructed with this method, including concrete, paver, and dirt/ gravel surfaces.
If anyone experiences any level of shock on a pool deck — even a slight tingle — it is a clear indication of inadequate bonding, and it exposes a potentially fatal risk. All pools should be safe and free from any shocks. If the pool builder can’t determine the cause and solve the problem, a utility company may be asked to assist. It may determine the pool system is unsafe and stop providing electrical power to the unsafe pool until the proper safety measures are installed. The only proven measure is to remove the existing deck, install an equipotential bonding grid of either rebar, welded
steel wire, or copper, and reinstall the deck. Retrofitting a paver deck with a proper equipotential bonding grid is not a huge ordeal or expense. Replacing a concrete deck, however, could bear a higher cost depending on the amount of concrete to remove and dispose.
Subject matter specialists at Consolidated Manufacturing, LLC (CMI) are available to answer questions and can also put pool professionals in touch with the proper utility liaison if there are any further concerns. If built properly, a pool should improve health and provide years of safe enjoyment. A few proper steps taken during development and construction will eliminate cause for concern, allowing swimmers to enjoy a refreshing and beautiful pool.
CMI has worked with national testing laboratories and industry organizations to address the issue of proper pool bonding.
One of those organizations is the Electric Power Research Institute (EPRI). A test procedure to determine if a pool is properly bonded was developed by the world’s leading authority on the subject. This 2-page file can be downloaded from www.cmiwebsite.com/validationprocedure/. Instructions are also found beginning on page XXXX of this issue of Service Industry News.
Grounding and Bonding
Correct grounding and bonding are uniquely essential in pool building. But knowing the correct rules and procedures isn’t something most pool builders and service professionals have had to learn.
What is the difference between grounding & bonding?
Knowing the difference between grounding and bonding is the first step in doing them correctly. Often, terms are used incorrectly or interchangeably, but they are different things.
Grounding – is the action of connecting part of a circuit to ground (or earth, depending on where you are from). This causes any voltage buildup in the connected parts of the circuit to dissipate into the ground. How well the voltage dissipates depends on the length and material of the grounding rod and how well the circuit is connected to it. That brings us to bonding.
Bonding – is the connecting of materials to ensure electricity can freely flow between those materials. One of the most common examples is connecting grounding wires to metal enclosures. Ensuring a good connection between surfaces is the key to proper bonding. Things such as paint, corrosion, or incorrect equipment can lead to poor bonding. Poor bonding means poor grounding — which can lead to danger.
There are numerous parts of both electrical circuits and structures that should be bonded together to manage voltage differential. In pool building, one of the missing ingredients has been equipment for attaching the grounding conductor to rebar. This, along with a few other items engineered by CMI, was created to ensure the highest of standards in grounding and bonding work during pool construction.
Grounding can also refer to a potentially dangerous situation of a ground fault. In this case, power is unintentionally shorted (fully or partially) to the grounded part of a circuit. This can even lead to metal cases on electrical equipment being positively charged, sometimes enough to be lethal.
Because water is a large contributor to creating ground faults (the classic “toaster in the bathtub” is an example), this is an especially large problem for pool areas. This type of grounding is what GFCI (ground fault current interrupter) outlets are designed to catch — causing them to trip and turn off, saving the end user.
What Is Stray Voltage?
What is stray voltage and why should you be concerned with it as a pool professional? If you’ve ever felt a shock from a pool deck, you may have already experienced stray voltage, and you might well know why it’s important to prevent. If you have felt it and survived, you’re one of the lucky ones. It can even be fatal, and as a pool professional, you want to protect your clients’ well-being, right? Read on to find out what causes contact voltage and what you can do about it.
What Causes Stray Voltage?
Stray voltage occurs when voltage exists in the ground. This means that loose electricity has “escaped” from a cable, a transformer, or another power source. It’s now traveling through the
ground, trying to dissipate. Realize that the natural path for electricity is the earth and that it tends to flow into the ground (think of a lightning strike).
Following the path of least resistance, the electricity will tackle whichever target is easiest. So when you have moisture (wet dirt, or say, a pool deck), the electricity will instead travel through that conductive material before dissipating into the ground. Wet concrete would be much easier for it to travel through than the natural ground!
There are ways to prevent stray voltage, but let’s find out why it can occur in the first place.
What Are The Sources Of Stray Voltage?
Stray voltage comes from many sources, such as:
• Cuts and nicks in buried lines.
• Faulty “drops” from overhead power lines (where power comes to a home from the main line).
• Damaged pads underneath transformers causing power “leaks.”
• And numerous other sources. The fact is, these voltages exist in the ground all throughout America. Even if a home’s electrical system is perfectly up to code, you could still be at risk from nearby sources.
Because you can’t possibly stop all the ways stray voltage is caused, you need to stop it from ever reaching you.
How Can I Protect Pool Areas from Stray Voltage?
There are several ways that a pool deck can be protected against stray voltage. One of the best ways is with equipotential bonding. This is essentially a copper wire grid that gets installed in the concrete deck and will attract any contact voltage, keeping the wet ground (and those on it) safe from the risk of shock.
Why Haven’t I Heard About Stray Voltage Before?
In years past, metal rebar was installed in all concrete flooring as standard practice (for concrete stability). As a result, electricity would choose to flow through metal rather than concrete, and stray voltage wasn’t really a concern.
When the industry started mixing concrete with other materials and rebar was no longer needed, stray voltage entered the picture. Subsequently, there have been far too many cases of injuries and even deaths from contact voltage.
Protect your clients by using equipotential bonding grids and mitigate the risk of stray voltage.
Reuben Clark, co-founder of Consolidated Manufacturing International, LLC, has been president of CMI for 22 years. He’s a proud member of the National Fire Protection Association, International Association of Electrical Inspectors, and the North Carolina Electrical Inspectors Association. He has participated in the National Electrical Code development process and worked on equipotential bonding projects with National Electric Energy Testing Research and Applications Center, Electric Power Research Institute.