Cara's Pool School — acid

Cyanuric Acid (also called Stabilizer or Conditioner) is added to outdoor pools to assist in prolonging chlorine's ability to withstand direct UV light from the sun. Often referred to as "sunscreen for your pool's chlorine", stabilizer prevents chlorine from quickly degrading to next-to-nothing in just a few hours. Keep in mind that high levels of cyanuric acid will require testing adjustments when checking Total Alkalinity levels (due to interference), and excessive levels may be a call to drain (full or partial) in order to dilute the concentration in the water. If in doubt, visit your local and trusted pool professional...