Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a white, odorless solid finds use as a precursor or a component of chlorine products used in swimming pool. Cyanuric acid is classified as “essentially nontoxic”. Cyanuric acid is marketed as a chlorine stabilizer for swimming pools.

Free chlorine can be protected from the effects of UV light in sunlight by the addition of Cyanuric acid, sometimes called stabilizer. Cyanuric acid is only recommended for outdoor pools and spas where sunlight can break down free chlorine quickly. There is NO chlorine benefit to feeding Cyanuric acid into indoor pools and spas.The recommend range for swimming pools, the optimal range for Cyanuric acid is 30-50 ppm. At levels above 50 ppm, pools reach the point of diminishing returns where the reduction in chlorine effectiveness and cost of buying Cyanuric acid outweighs the benefits. Some health departments regulate the level of Cyanuric acid in a pool, some indicating a maximum of 30ppm and others as high as 100ppm.

There are two ways by which Cyanuric acid is introduced into the pool. The first is by the addition of Cyanuric acid, the second is by the use of stabilized chlorine. Stabilized Chlorine tablets come in three forms from three and one inch circular tablets, a stick form and finally a granular form. Regardless of the form, the chemical composition is either dichlor or tri-chlor, these products when consumed breakdown to Cyanuric acid.Some health departments regulate the level of Cyanuric acid in a pool, some indicating a maximum of 30ppm and others as high as 100ppm.

For whatever reason to reduce the Cyanuric level there is essentially three ways, The first is to drain part of the water from the pool and replace it with water that does not contain Cyanuric acid (Tap Water). The second is to use another form of chlorine that does not contain Cyanuric acid, this prevents Cyanuric acid from going higher and with rainwater and backwashing over time this will bring down the Cyanuric acid level. While there is a third way is to reduce Cyanuric acid level the use a chemical known as melamine is not recommended. Introducing Melamine into the pool will cause the water to become cloudy and most filters would have difficulty in removing these very fine particles. One pound of melamine will reduce the Cyanuric acid level by 12 ppm in a 10,000 gallon pool.

Controlling the type of chlorine you use is the best way to control Cyanuric acid levels. Switching to a non-CYA based sanitizer such as liquid chlorine, liquid bleach, calcium hypochlorite or lithium hypochlorite will lower CYA only because these chlorine products do not contain Cyanuric acid.

Testing for Cyanuric acid:

Melamine combines with cyanuric acid and related compounds to form melamine cyanurate. This compound forms a precipitate, which makes the water cloudy, how cloudy the water becomes is a measure of the Cyanuric acid level in the pool.