High Stabilizer/Cyanuric Acid

Crystal clear water is not always safe, and cloudy water illustrates evidence of strongly alkaline water. An excessively high stabilizer level will have the following effects:

  • Slows down chlorine’s reaction time. Cyanuric acid forms a weak bond with the free chlorine present in the pool’s water, protecting it from the sun’s UV rays to decrease loss. It has been shown that, when properly managed, cyanuric acid decreases the quantity of chlorine required to maintain the minimum residual chlorine level in outdoor pools.
  • Seriously interferes with total alkalinity. Cyanuric acid affects total alkalinity by behaving similarly to bicarbonates and carbonates. A correction factor must then be applied when measuring alkalinity in pools and spas.
  • May cause cloudiness. In some cases, an elevated cyanuric acid level can cause cloudiness as visible as a white veil. Cyanuric acid can be successfully eliminated only by diluting the pool or spa with fresh water.
  • Can “block” chlorine. When the cyanuric acid level is high enough, chlorine loses its efficacy to destroy bacteria, algae, or organic waste, which can cause cloudiness and give chlorine level readings of zero.
  • The optimal or stable cyanuric acid level is between 30 and 50 ppm.
    • Keep in mind that ppm is the concentration unit that indicates that one part of solid is dissolved in one million parts of water (mg/L). At concentrations lower than 30 ppm, chlorine will dissipate, while at concentrations equal to or higher than 50 ppm, there are risks of cloudiness and chlorine “blockage”.


  • The only way to lower the cyanuric acid level is to drain a percentage of the pool.
  • Drain half the pool, refill pool with fresh water. Run filter for 24 hours, and then retest stabilizer (cyanuric acid) level.
  • Using unstabilized chlorine that does not contain cyanuric acid, such as Chlor, Lithium or Chlor Tabs is also an option to prevent further additions of stabilizer to pool water.