Being in a swimming pool during a lightning storm is highly dangerous. Lightning is an immense electrical discharge that carries currents averaging 25,000 amps and voltages in the hundreds of millions. Immediate action is required when a storm approaches, as the water acts as an efficient conduit for this energy. The combination of water and conductive materials in a pool environment creates a substantial electrocution risk.
Understanding Electrical Conductivity in Pool Water
Pool water becomes an electrical conductor due to dissolved ions, which allow current to flow easily. While pure water is a poor conductor, pool water contains various minerals, salts, and chemicals like chlorine. These substances dissolve to create charged particles that carry electrical energy across the water’s surface.
The total dissolved solids in pool water increase its electrical conductivity. When lightning introduces a massive electrical charge, this ion-rich water instantly disperses the current. The electricity spreads rapidly across the surface, creating a danger zone.
The current is mostly confined to the top few centimeters of water, meaning that getting deeper offers no protection. Because the current travels laterally across the surface, an electric field can extend for several meters from the strike point. This rapid conduction means a swimmer does not need to be near the point of impact to be at risk of severe injury or death.
How Lightning Reaches a Swimming Pool
A direct strike to the water or a person is the most dangerous scenario, instantly delivering the full electrical charge. However, lightning often targets the tallest objects nearby, making indirect strikes the primary risk. Indirect strikes channel electricity into the pool area through three main routes.
Ground current is the most frequent indirect threat, occurring when lightning hits an object like a tree, utility pole, or the ground near the pool. The electrical charge travels through the earth, which may be wet and conductive, and is channeled into the pool structure. This current can enter the water through the pool shell, surrounding decking, or underground plumbing and electrical systems.
Lightning can also reach the water via conduction through infrastructure connected to the pool. Metal objects act as highly efficient conductors, including:
- Ladders
- Railings
- Diving board stanchions
- Perimeter fences
Electrical power lines and buried metallic pipes leading to the pool’s filtration and lighting systems can also deliver the charge directly to the water.
Essential Safety and Evacuation Procedures
At the first sound of thunder or sight of lightning, the pool and surrounding area must be evacuated immediately. The “Flash-to-Bang” method is a common safety measure: every five seconds between the flash and the sound of thunder equals roughly one mile of distance. Evacuation is required if the count is 30 seconds or less, indicating the storm is within six miles.
Once evacuated, individuals must seek shelter in a substantial, fully enclosed building that provides a safe, grounded environment. Open-sided structures such as gazebos, picnic shelters, or sheds do not offer adequate protection and must be avoided. Individuals should remain sheltered for a minimum of 30 minutes after the last observed thunder or lightning flash.
The “30-minute rule” is a standard safety protocol because lightning can strike from the trailing edge of a storm cloud many miles away. For indoor pools, the risk is lower but not eliminated, as current can travel through the building’s plumbing and electrical systems. During a storm, indoor pool users should avoid showering or using faucets and remain away from hard-wired electrical equipment.