Water Stabilizer refers to cyanuric acid and it’s presence in swimming pool water. Stabilizer is measure in parts per million (ppm) and the desired range is 30 – 80ppm. As chlorine breaks down quite rapidly in sunlight Stabilizer is used to protect chlorine against UV degradation, making the chlorine last longer in the water.
Maintaining a proper level of Stabilizer saves money in chlorine and is part of a goood overall water balance.
Note that some types of chlorine such as Super Chlor and Tri-Chlor already contain stabilizer and the constant use of these products will increase your stabilizer level too high.