There are several different ways that the potential for electric shock drowning can be present in a swimming pool.
Consider the following scenarios:
• A concrete pool with imbedded rebar (partially conductive) in contact with the surrounding earth with an ungrounded metal ladder not in contact with water.
• A fiberglass (insulating) pool with in-water feature (such as a pool light) connected to earth ground with an ungrounded metal ladder not in contact with water.
In both of these cases, the pool water can carry current to ground.
If an electrical malfunction causes the metal ladder to become connected to a hot AC voltage source, no current will flow because there is no contact between the ladder and ground.
However, a person entering or leaving the pool who touches the ladder while in contact with the pool water will be subject to potentially lethal electric current because the person provides the path to ground through the pool walls or fixture.
(That is, unless the GFCI shuts off the voltage.)
Consider a second scenario:
• A fiberglass (insulating) pool with in-water features (such as a pool light) not connected to earth ground and a metal ladder connected to earth ground but not in contact with the water.
If an electrical malfunction causes the ungrounded water feature to become in contact with a hot AC voltage source, (or a hot electric line falls in the water) no excess current will flow because there is no contact between the water and the ladder. However, a person entering or leaving the pool in contact with both the ladder and the water may experience a lethal current as they become the channel by which the current can go to ground through the ladder.
Consider a third type of hazardous scenario:
• A concrete pool with imbedded rebar (partially conductive) in contact with the surrounding earth.
• A fiberglass (insulating) pool with in-water feature (such as a pool light) connected to earth ground.
In both of these scenarios, the pool water can carry current to ground should a malfunction occur. If a malfunction occurs such that a pool light becomes connected to a hot AC voltage source (or a live electricity source falls in the water), the current density and voltage gradient will be largest near the malfunctioning fixture or live source, as well as any other grounded in-water fixtures that will become current sinks. Thus, a person in the water can be exposed to a potentially lethal electric current depending on how close they are to the malfunctioning feature, live source, or grounded, inwater features. In these scenarios, the current density and voltage gradients will also depend on the size and location of the current source; the source voltage; the size and shape of the pool; the pool wall’s electrical conductivity; the sizes and locations of the grounded, in-water features; and the pool water conductivity.
Based on the potential hazards discussed above, the following measures should be followed for preventing electric shock drowning in people:
• GFCI protection of in-water lights, near-water lights, receptacles, pumps, heaters, and of other nearwater electrical equipment.
• Bonding and grounding of any near-water or in-water ladders and railings, electrical conduits, junction boxes, and other metal fixtures.
• Bonding and grounding of pool water for otherwise insulated pools (fiberglass/vinyl-lined).
• Appropriate distance between the pool and any overhead power wires or nearby electrical devices so hot wires cannot fall in the pool.
Video available on NFPA.org
