You may have a reading for ‘stabilizer’ on the bottom of your chlorine hot tub test strips. Stabilizer, also known as cyanuric acid, is used in hot tubs that sanitize with chlorine to counteract UV light, which naturally breaks down chlorine. Stabilizer prevents UV light from breaking down chlorine by binding to the chlorine molecule, which frees up the chlorine to eliminate bacteria and other contaminants in your hot tub.
The recommended level for stabilizer is 30-50 ppm, but the closer this number is to 30, the better, as when stabilizer rises above 50 ppm it starts to make chlorine less effective and eventually practically ineffective.
What to do if your stabilizer reading is 0 or low
Fresh water is unstabilized; when your hot tub is freshly filled, there is no stabilizer. Since chlorine granules are stabilized, your stabilizer levels will increase over time. As chlorine eliminates bacteria and contaminants, the chlorine disappears, but the stabilizer remains. After a hot tub fill, your stabilizer will reach the recommended 30 ppm within a few weeks. You should separately add stabilizer or cyanuric acid to your hot tub.
What do I do if my stabilizer reading is high?
Eventually, your hot tub’s stabilizer level will rise above 50 ppm, and when it does, it begins to ‘over-stabilize’ the chlorine. When chlorine is over-stabilized, chlorine becomes less effective, and higher free chlorine levels are required - this also can cause cloudy water. When stabilizer levels reach 60 ppm, chlorine becomes practically ineffective.
Stabilizer can only be removed from a hot tub by diluting the water with fresh water. Partially draining and refilling your hot tub water will lower stabilizer levels (remember to turn off your hot tub before lowering your water). When you drain and refill your hot tub completely, the stabilizer level resets to 0 ppm - we recommend doing this quarterly.