Pool Stabilizer Calculator
Stabilizer (cyanuric acid, CYA) protects chlorine from sunlight. Enter your reading and target to get how much to add, or how much water to replace if it's too high.
Quick answer: Raising stabilizer (CYA) by 10 ppm in a 10,000-gallon pool takes about 13 oz of cyanuric acid. The only way to lower CYA is to drain some water and refill.
Checked against 4 published sources (see them). Updated October 2026.
- Raises CYA by
- 20 ppm
How it works
Cyanuric acid is nearly pure as sold, so it follows the base rule: about 13 oz raises CYA 10 ppm in 10,000 gallons (Indiana Department of Health, PHTA and Wojtowicz agree).
CYA dissolves slowly and takes days to show up fully on a test. Don't add more until you've retested after about a week.
If CYA is too high, the only fix is replacing water. Draining a fraction of the pool and refilling with fresh water lowers CYA by that same fraction.
Tips
- Dichlor and trichlor add CYA every time you use them, so CYA creeps up in pools that use tablets.
- Liquid chlorine, cal-hypo and salt cells don't add CYA.
- The CDC recommends not using CYA in hot tubs.
Sources
We checked the math on this page against:
- Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool
- Pool & Hot Tub Alliance: Pool & Spa Management (2021), Appendix B
- Wojtowicz, "Swimming Pool and Spa Water Chemical Adjustments," Journal of the Swimming Pool and Spa Industry (2004)
- CDC Model Aquatic Health Code, 2024 edition
Frequently asked questions
How much stabilizer for a 15,000-gallon pool?
About 20 oz (1 lb 4 oz) raises CYA 10 ppm. From 0 to 40 ppm takes about 5 lb.
What should CYA be?
Many pools keep it at 30–50 ppm. The CDC's Model Aquatic Health Code caps it at 90 ppm. Some states set lower limits for public pools.
How do I lower CYA?
Drain part of the water and refill. To go from 100 ppm to 50 ppm, replace about half the water.