The purpose of this Tech Letter is to acquaint subscribers with the issue of aquatics safety and lightning protection for indoor pools. Lightning protection precautions for indoor pools is an issue that poses concerns for recreational facilities in terms of safety, risk management, and loss control programs. The topic is also one that LPI frequently receives questions about. Concerns revolve around whether or not the same thunderstorm safety precautions for outdoor pools should be applied to indoor facilities. Should indoor pools be evacuated, or should these pools be considered safe to use during a storm? In conjunction with National Preparedness Month, LPI provides clarification on this issue and resources for follow-up.
When examining this issue, there are many variables for consideration under lightning attachment conditions. If the facility’s structure has a complete lightning protection system: 1) materials and methods in accordance with the National Safety Standards for Lightning Protection Installation (LPI 175, NFPA-780, UL-96A); 2) installed by a qualified LPI-certified contractor; and 3) certified by a third-party inspection service such as LPI-IP, then the individuals inside the structure would be considered to be as safe as we can make them, regardless of the internal systems or functions of the construction-this is the “short” answer.
However, in a scenario with no lightning protection system, consideration needs to be given as to what path the lightning will follow to reach earth ground. The lightning could potentially travel along structural framing members outside the perimeter of the pool itself, it could seek metallic piping systems, or equipment wiring could be the source that provides the path to ground. Without a lightning protection system for the structure, there is no control mechanism, resulting in lightning seeking any number of paths or lack thereof.
A secondary problem concerns the arcing that occurs between separately grounded systems. When one metallic system becomes energized by lightning or anything else, any other independently grounded system will be at a different ground potential. Different ground potentials cause current flow, either within equipment connected to two or more systems, or if they are proximate, arcing may occur. Bonding these building grounded systems together at their entry to structures and at a point where equipment interconnects multiple systems, minimizes any potential difference problems, and is now required by the National Electric Code (NFPA 70), as well as the lightning protection safety standards.
Now to understand how the pool water itself, plays a part in this equation, let’s reference a well-known seventh-grade science class experiment. In the experiment, we attempt to power a lamp with leads by a battery run through a jug of distilled water. The problem is that we don’t use any pure water. The salt water in the ocean is a much better conductor than fresh lake water because of the level of particulate matter that conducts electricity, but they both conduct. Our drinking water is treated for “purity” and these particles conduct. Swimming pool water is further treated to inhibit bacterial growth, which adds potential conductive capability. Now we are faced with so many variables, that it becomes pretty difficult to provide a strict analysis to conclusion…
How conductive is the pool’s water?
What grounded systems are attached to what points of the pool water?
Where is the lightning coming from, and where will it head to earth ground?
These variables make it difficult to provide any blanket statement about personal contact with pool water, either outdoors or in an indoor unprotected structure.
Due to the difficulty to predict a dangerous condition with accuracy, most authorities will implement policies of clearing a pool under storm conditions in order to mitigate any potential contact between a really good conductor (the human body) and the potentially conductive pool water. Even with the scenario of clearing the pool, another problem to deal with, presents itself-that of human nature. Upon clearing the pool, a facility’s patrons may likely go into the shower room and stand near metallic plumbing systems and metallic drainage systems. Or they might get on the phone to call for a ride, thus connecting with a landline that could provide a path for lightning to follow. Additionally, if those same patrons run out to their cars in the parking lot, they further expose themselves to direct strikes (until they get into the safety of their cars).
When considering all of the variables and possible scenarios, the subject of aquatics safety and lightning protection for indoor pools in not an easily solvable situation.
Since lightning’s behavior is unpredictable, the best approach for indoor pool safety, may be for a recreational facility to develop a conservative, yet common sense plan for management responsiveness and preparedness. Ultimately, the ideal approach is to address safety provisions during design and construction of the facility by including a lightning protection system for the structure.
Facilities seeking safety guidelines for their members and guests may want to refer to the following, additional sources for information on the internet at:
National Weather Service/Lightning Safety
YMCA Services Corporation Indoor Pool Safety Guidelines
National Athletic Trainers Association (NATA)
National Recreation & Park Association (NRPA)/ Parks & Recreation
The Lightning Protection Institute (LPI) is a not-for-profit, nationwide group founded in 1955 to promote lightning safety, awareness and education. LPI is a leading resource for lightning protection and safety standard-compliant system requirements. Visit the LPI website at www.lightning.org
to locate a LPI-certified specialist in your area.