Cyanuric Acid

Also Known As: Triazinetrione, Isocryanurates, Stabilizer

Cyanuric acid is used to stabilize chlorine, maintaining chlorine’s effectiveness in sunlight. It forms a weak bond with free chlorine, which helps the chlorine resist degradation due to ultraviolet light.

In the proper balance, cyanuric acid can help reduce chlorine usage, saving money and keeping swimmers more comfortable. Chlorinated isocyanurates, like dichlor and trichlor, already contain cyanuric acid.

Over time, cyanuric acid will increase in concentration, which reduces the overall effectiveness of the chlorine. In this situation, bacteria and other pathogens may be allowed to multiply. Outdoor pools should have a free chlorine level of at least two parts per million (ppm). The optimal range for cyanuric acid is between 30 and 50 ppm, and it should not exceed 100 ppm. Pool water treated with cyanuric acid should be tested regularly, to insure that the proper levels are maintained.

Because most chlorine compounds include cyanuric acid, it is recommended that the stabilizer be added only at the beginning of the pool season. When chlorine is added later, the cyanuric acid levels should remain steady. Cyanuric acid should be dissolved in a bucket of water before it is added to the pool water. The chemical breaks down slowly, so adding it to a vinyl-lined pool before dissolving could cause damage to the lining.