An article that appeared in the November/December 2008 issue of Aquatics International stated that there was no longer a need to clear indoor swimming pools during a thunderstorm. The article noted that there have been no documented deaths from lightning in indoor pools and that since the National Electric Code requires bonding and grounding, swimmers would be protected in the water. What most people will fail to take away from this article is that the author gave two necessary prerequisites for such a change in protocol.
While it is true that current codes require bonding and grounding of the metallic elements in the pool area, most existing pools do not meet that standard and never have because they were built under different regulations. Many new pools do not comply because though the basic grid is bonded they have added stainless steel lifeguard chairs or metal bleachers that are not connected with the grid. To complicate the issue, over time concrete and the pool area environment can deteriorate bonding. Thus, just because a pool was built to code does not necessarily mean that it remains uncompromised, and to certify that a pool is presently grounded and bonded is an expensive process that must be repeated periodically to ensure that deterioration has not occurred and that new metallic elements have not been introduced.
The second prerequisite, a lightning protection system, is not a common component of pool buildings, thus further minimizing the claim that clearing indoor pools during lightning storms is unnecessary. From just the standpoint of electrocution the statement is true. It is just not true for the vast majority of pools in this country.
The article also states “’In fact, a pool closure policy is in violation of the National Electric Code section 250.4(A)(1) and you will be subject to regulatory enforcement.’ Dr. Weiss adds that facility operators must understand they are breaking the law by closing indoor pools.” NFPA 70 § 250.4(A)(1) says “Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.” Neither the quoted electrical code nor the more applicable National Electric Code article 680 (Swimming Pools [et al]) mentions either pool closure during electrical storms or regulatory enforcement; we have contacted NFPA for a confirmation.
The good news is that national statistics do not include any deaths from lightning to people in indoor pools. Perhaps that is more because the practice is to clear the pools than because lightning does not strike pool areas. There are several documented instances of lightning striking indoor pools through glass or open windows and contacting the pool bottom, bleachers, or a lifeguard chair.
The above comments basically address only death from electrocution. Pools with large expanses of glass have an additional exposure – not only may the glass be an avenue through which lightning may enter the facility, but a close strike may shatter windows. If the structure has a lightning protection system, that potential may be increased because lightning protection systems do not repel lightning – they attract it to a specific point so the energy can be directed to ground without damaging the facility. A close strike creates a significant sonic disturbance that could cause glass to fall on those in the pool area.
The Redwoods Group, American Red Cross and National Lightning Safety Institute continue to recommend the proactive action of removing swimmers from indoor pools as a lightning storm approaches and until after it passes. This protocol includes keeping swimmers out of the showers, away from telephones, and clear of metallic objects or large expanses of glass until after the storm passes. Leaving the premises is also not advised.
We are in agreement that people come to indoor pools to have fun; however we must also remain diligent in clearing the indoor pools during thunderstorms. There has been a tremendous amount of technology created to more accurately track thunderstorms. These affordable systems may decrease the time out of the water for the swimmers and help to decrease the dissatisfaction of the swimmers at having to clear the water.
For the safety of indoor pool swimmers, as well as for the sake of our own consciences, we are retaining our historic stance and will continue to encourage the clearing of indoor pools during a thunderstorm.