Indoor swimming pools offer a degree of protection from thunderstorms, but they are not entirely immune to the dangers of a lightning strike. While the risk of a direct strike causing harm to a person inside a substantial, modern building is low, the electrical charge from a nearby strike can still pose a threat to those in or near the water. Water and the metal systems surrounding it can act as conductors for the immense electrical energy released by lightning.
How Lightning Enters Indoor Pool Facilities
A lightning strike does not need to hit the pool building directly to create a hazard inside, as the electrical charge can enter a structure through conductive materials connected to the outside ground. The primary risk comes from the electrical current traveling through the building’s utility systems. If lightning strikes the ground, a nearby tree, or an adjacent structure, the massive surge of energy can follow underground pathways.
Metal plumbing pipes are a significant vulnerability, as the pool’s filtration and circulation systems are fundamentally connected to the building’s water inflow and outflow. This network of metal pipes acts as a conduit, allowing the high-voltage electrical charge to enter the facility and reach the pool water itself. Similarly, the electrical wiring for pool pumps, heaters, underwater lights, and automated chemical systems can also channel a dangerous power surge into the pool area.
Structural components, such as exposed metal beams or rebar within the concrete, can also conduct the charge from an external strike. Because swimming pool water contains impurities and dissolved minerals from chemical treatments, it is more conductive than pure water, making it a viable medium for the current to spread once it enters the basin. Even with modern grounding and bonding systems designed to dissipate electrical energy safely into the earth, no system is completely foolproof against the immense power of a lightning bolt.
High-Risk Areas Within the Pool Environment
Once the lightning’s electrical energy has entered the facility through conductive pathways, it can quickly energize specific locations and objects. The water itself is a high-risk area because it is directly connected to the pool’s metal filtration and plumbing infrastructure. Anyone in the pool is in contact with this conductive water, which can potentially carry the charge throughout the entire volume of the basin.
Metal fixtures that swimmers routinely touch pose an immediate hazard due to their direct connection to the building’s structure or plumbing. This includes stainless steel ladders, railings, and starting blocks, which can become energized if a current passes through their supports. Even areas like showers, sinks, and water fountains are dangerous because they are directly linked to the metal pipes that brought the electrical surge inside the building.
Areas near large windows or exterior doors should also be avoided during a thunderstorm. Although glass itself is an insulator, a nearby lightning strike can cause the air pressure to rapidly change, which may shatter the glass. Moving away from these openings prevents injury from flying debris and maintains a greater distance from potential entry points for the electrical energy. Staying away from electrical outlets and equipment like lifeguard stations with communication systems is also necessary, as these can carry a surge.
Essential Safety Procedures
Facility operators and patrons must follow clear protocols to ensure safety when lightning is in the vicinity. The universally accepted standard for aquatic facilities is the “30-minute rule,” which mandates that all activities cease at the first sound of thunder or sight of lightning. This rule applies equally to indoor pools due to the conductive nature of the facility’s systems.
Immediate action requires all patrons to exit the water and move away from the pool deck. The 30-minute timer for re-entry should not begin until 30 minutes have passed since the last observed lightning flash or clap of thunder. This conservative waiting period is necessary because lightning can strike miles away from the main storm cell and often occurs after the heaviest rain has passed.
Patrons should seek shelter in a safe, interior area of the building, such as a locker room or lobby, and avoid contact with all potential conductors. This means refraining from using corded telephones, touching metal plumbing fixtures, or using showers and sinks until the all-clear is given. Moving to a location with no direct connection to the building’s electrical or plumbing systems significantly reduces the risk of injury from a lightning-induced electrical surge.