Chlorine tablets are common sanitizers for pools and spas, effectively disinfecting water when used according to directions. However, these concentrated chemical compounds are inherently dangerous and corrosive in their solid form. Understanding their chemical nature and the risks involved is necessary for safe handling and use.
Chemical Composition and Formulation
The primary active ingredient in most chlorine tablets is trichloroisocyanuric acid, often called “Trichlor,” which has a high available chlorine content. When this compound dissolves in water, it slowly releases the active disinfectant, hypochlorous acid. Cyanuric acid (CYA) is also included in the formulation as a byproduct of the dissolving process.
CYA acts as a stabilizer, protecting the chlorine from being rapidly degraded by the sun’s ultraviolet rays. This stabilization allows the chlorine to remain active for longer periods. However, the tablets are highly acidic, with a pH of around 2.7. This low pH means the tablets continuously lower the pool’s overall pH and total alkalinity as they dissolve.
Acute Handling and Storage Risks
The solid tablets pose immediate and severe hazards before dissolution. Trichlor is a strong oxidizer, meaning it can intensify a fire and react violently with combustible materials. Storing the tablets near heat, sparks, or flammable items creates a significant fire and explosion risk. The tablets are highly reactive and must never be mixed with other pool chemicals, especially different types of chlorine, acids, or ammonia-based products. Mixing these substances can cause a violent reaction, releasing toxic gases like chlorine gas.
Direct physical contact with the solid tablets or their dust can cause severe skin and eye damage. When the chemical contacts moisture, such as sweat or mucous membranes, it produces corrosive substances. Inhaling the dust or fumes can cause serious respiratory irritation. For safety, tablets should be stored in their original, tightly closed container in a cool, dry, and well-ventilated area, away from all incompatible materials.
Safety Implications for Swimmers
The use of chlorine tablets introduces challenges to water quality that directly affect swimmer safety. Chlorine reacts with organic compounds like sweat and cosmetics, creating chemicals called chloramines, or combined chlorine. Chloramines are the source of the strong “chlorine” smell and are responsible for eye and skin irritation. They accumulate in the air, especially in indoor pools, and can cause respiratory irritation for swimmers and spectators.
The highly acidic tablets constantly drive down the pool’s pH and total alkalinity, leading to acidic water conditions. Water that is too acidic (below the ideal pH range of 7.4 to 7.8) irritates swimmers’ skin and eyes. Acidic water also corrodes pool equipment and can damage the pool’s surface materials over time.
A complication arises from the stabilizer, cyanuric acid (CYA), which is continuously added with each tablet. While CYA protects chlorine from the sun, excessive levels (often above 50 parts per million) significantly slow the chlorine’s ability to kill harmful bacteria and microorganisms. This “over-stabilization” creates a false sense of security where the pool may show adequate total chlorine, but the effective free chlorine is too slow to sanitize the water safely. The only way to correct excessively high CYA levels is to partially drain the pool and refill it with fresh water.
Essential Safety Protocols for Usage
To minimize inherent risks, users must follow strict protocols when handling chlorine tablets. Personal Protective Equipment (PPE) is necessary, including chemical-resistant gloves and protective eyewear, to prevent corrosive contact. Containers should only be opened in well-ventilated areas to avoid inhaling irritating dust or fumes.
The tablets must never be placed directly into the pool or skimmer basket, as this concentrates the corrosive acid and can cause permanent damage to the surface or plumbing. Tablets should be dispensed using an approved chemical feeder or a floating dispenser, which controls the dissolution rate. Regular testing of the pool water is necessary to monitor the effects on water chemistry. Users must frequently check the pH, free chlorine, and cyanuric acid levels to ensure the water remains safe for swimmers and equipment.