By Kevin Vlietstra
Chlorine is a vital component for maintaining the safety of pool water for swimmers. Its primary function is to serve as a sanitizer, but it also has the added capability of acting as the primary oxidizer of waste and preventing the proliferation of algae. When there is an abundance of chlorine available, it can efficiently perform all three of these functions. However, in situations where chlorine is in short supply, it becomes necessary to introduce supplementary substances. These supplements can serve to either reduce the overall quantity of chlorine required or extend the lifespan of the existing chlorine within the water.
One common additive used for this purpose is cyanuric acid (CYA). It is frequently used to stabilize, safeguard, and conserve chlorine, regardless of whether it is in tablet or liquid form. This article will primarily focus on CYA’s role in preserving chlorine and delve into its impact on water quality as it accumulates in the pool.
Understanding the role of CYA
In discussions concerning chlorine and cyanuric acid (CYA), it is essential to provide an overview of the two categories of chlorine used for water treatment: chlorine with stabilizers and chlorine without stabilizers. Chlorine types lacking stabilizers encompass sodium hypochlorite (commonly known as liquid chlorine bleach) and calcium hypochlorite (often abbreviated as cal-hypo). On the other hand, chlorine varieties with stabilizers are typically referred to as “trichloro” or “dichlor.” These product names reflect their respective manufacturing processes. For instance, trichloroisocyanuric acid (trichlor) is produced by reacting certain ingredients with CYA to generate a concentrated granular chlorine.
Upon the application of dichlor or trichlor to fresh water, CYA becomes introduced into the pool environment. The stabilized chlorine also yields hypochlorous acid (HOCl), which binds with the CYA. Consequently, HOCl retains its effectiveness for a longer duration when the pool is exposed to outdoor conditions and ultraviolet (UV) light. Initially, even at just one part per million (ppm) of CYA, chlorine remains in the water for an extended period compared to its absence. As the CYA concentration reaches approximately 25 ppm, a more significant amount of chlorine (HOCl) is shielded from degradation in the presence of UV light.1 This not only prolongs the presence of chlorine in the water but also translates into time and cost savings for pool owners.
