Liquid chlorine does not raise cyanuric acid (CYA) levels in pool water. This common household pool chemical, often sold as sodium hypochlorite solution, is an unstabilized form of chlorine. CYA is a separate compound added to outdoor pools to act as a stabilizer, shielding the chlorine from the sun’s ultraviolet rays. The confusion arises because some other popular chlorine products do contain CYA, which increases its concentration in the water. Understanding the distinction between stabilized and unstabilized chlorine products is fundamental for pool owners.
The Chemical Makeup of Liquid Chlorine
Liquid chlorine, also known as liquid bleach or sodium hypochlorite (NaOCl), is simply a solution of chlorine and water. When added to a pool, it dissolves and forms hypochlorous acid (HOCl), which is the active sanitizing agent. This solution contains no cyanuric acid or calcium.
The primary byproducts of this reaction are salt (sodium chloride, NaCl) and water. Since sodium hypochlorite does not introduce CYA, its use does not contribute to the accumulation of stabilizer. This makes liquid chlorine a preferred option for pool owners trying to manage or lower their existing CYA concentration.
How Cyanuric Acid Works in Pool Water
Cyanuric acid reduces the rate at which chlorine is destroyed by UV light. In an outdoor pool without CYA, half of the free chlorine can be lost in under an hour of direct sunlight. The CYA molecule forms a temporary, weak bond with the chlorine, protecting it from rapid degradation.
This protective mechanism allows the chlorine to remain in the water longer, extending the life of the sanitizer. The recommended concentration for CYA is between 30 and 50 parts per million (ppm) to provide adequate protection without hindering effectiveness. Maintaining this range ensures the chlorine is shielded from the sun while remaining available to sanitize the water.
The concern about rising CYA levels is that too much stabilizer suppresses the concentration of active hypochlorous acid (HOCl). As CYA levels climb past 50 ppm, the chlorine’s ability to kill pathogens and algae slows significantly, requiring higher free chlorine levels to compensate. Since CYA does not evaporate or get consumed, the only way to reduce a high concentration is by partially draining the pool and adding fresh water.
Chlorine Sources That Increase Cyanuric Acid Levels
The main source of CYA accumulation comes from stabilized chlorine products, specifically Dichlor and Trichlor. These solid forms of chlorine are manufactured by bonding chlorine atoms directly to the cyanuric acid molecule. This allows pool owners to add both chlorine and stabilizer simultaneously.
When these stabilized products dissolve, they release both active chlorine and the cyanuric acid molecule. Dichlor is a granular product that adds approximately 0.9 ppm of CYA for every 1.0 ppm of free chlorine introduced. Trichlor, typically found in tablet form, adds about 0.6 ppm of CYA per 1.0 ppm of free chlorine.
Regular, long-term use of Dichlor or Trichlor leads to a steady increase in the pool’s CYA concentration. This constant addition causes stabilizer levels to rise over time, often leading to confusion regarding the use of liquid chlorine. Switching to an unstabilized option like liquid chlorine allows owners to maintain chlorine levels without adding more CYA.