Water is often perceived as a universal conductor of electricity, which can lead to safety misjudgments. While water can conduct electricity, pure water, like distilled or deionized water, is a poor conductor. It is typically the impurities found within most water sources that enable the flow of electrical current.
How Water Conducts Electricity
Water’s ability to conduct electricity stems from dissolved ions, which are atoms or molecules carrying an electrical charge. Pure water, composed only of H₂O molecules, has very few free ions to carry a current, making it an electrical insulator. Its electrical conductivity is very low, typically between 0.5 to 3 microSiemens per centimeter (µS/cm).
Common water sources, such as tap water, lake water, or ocean water, contain dissolved minerals, salts, and other substances. These substances dissociate into charged ions when dissolved. For instance, sodium chloride (table salt) separates into positively charged sodium ions and negatively charged chloride ions.
These mobile ions act as charge carriers, allowing electricity to move through water. The greater the concentration of these dissolved ions, the more pathways exist for electrical current to flow. This principle explains why different types of water exhibit varying levels of electrical conductivity.
What Makes Water More or Less Conductive
Several factors influence how effectively water conducts electricity. The concentration and type of dissolved substances play a significant role. Water with a higher concentration of dissolved salts and minerals, such as seawater, leads to much higher conductivity. Conversely, water with fewer dissolved impurities, like rainwater or highly filtered water, will have lower conductivity.
Temperature also impacts water’s conductivity. As water temperature increases, dissolved ions gain more kinetic energy and move faster. This enhanced mobility allows them to carry electrical charges more efficiently, resulting in increased conductivity. A temperature increase of just one degree Celsius can raise electrical conductivity by 2-3 percent.
While voltage is necessary to drive current through water, its inherent conductivity is primarily determined by composition and temperature. A higher applied voltage can overcome more resistance, but water’s capacity to conduct remains tied to the availability and mobility of its dissolved ions. Inorganic dissolved solids such as chloride, nitrate, sulfate, sodium, and calcium ions contribute to this conductivity.
Electricity’s Path Through Water Over Distance
When electricity enters a body of water, it disperses in all directions from the source, creating an electrical field. This phenomenon is similar to ripples expanding outwards when a stone is dropped into a pond. The intensity of the electrical current diminishes rapidly as it moves further from its origin.
This reduction in intensity is due to increased resistance with distance, causing both voltage and current density to drop. The water itself absorbs and scatters electrical energy, a process known as attenuation. In highly conductive water, like seawater, this attenuation is more pronounced because abundant ions absorb more energy.
While the electrical effect becomes significantly weaker with distance, it does not necessarily reach a fixed “end point” where it ceases to exist. Instead, the current becomes too weak to pose a significant hazard or be detectable. For example, a lightning strike in the ocean would dissipate spherically, rapidly reducing its impact far from the point of entry.
Staying Safe Around Electricity and Water
The interaction between electricity and water can pose serious risks, including electric shock and electrocution. Even seemingly low voltages can be hazardous in conductive water environments. This danger is amplified by faulty wiring or damaged electrical equipment that allows current to enter the water.
One significant risk is Electric Shock Drowning (ESD), where an electrical current in water causes muscle paralysis, leading to a person being unable to swim and subsequently drowning. This can occur in swimming pools, hot tubs, or bodies of water near docks and marinas with compromised electrical systems.
To prevent such incidents, avoid using electronic devices near water sources. Exercise extreme caution around downed power lines in wet conditions, as water can conduct electricity over a wider area. Ensure all electrical wiring and equipment near swimming pools, spas, or other bodies of water are regularly inspected and maintained by qualified professionals.