Calculate exactly how much stabilizer (CYA) to add to your pool for optimal chlorine protection from UV degradation.
Don't know? Use our Pool Volume Calculator
Test with CYA strips or kit
Ideal: 30-50 PPM
Pure granular CYA is most cost-effective
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Dissolve CYA in a bucket of warm water first, then pour slowly around the pool perimeter.
Cyanuric acid (CYA), also known as pool stabilizer or conditioner, protects chlorine from rapid degradation by ultraviolet sunlight. This calculator helps you determine exactly how much CYA to add based on your pool volume and current levels.
Cyanuric acid is a chemical compound that bonds with free chlorine in your pool to form a more stable molecule. This stabilized chlorine is protected from UV rays, dramatically extending its lifespan in the water. Without CYA, chlorine in an outdoor pool can be destroyed by sunlight within hours.
CYA is sometimes called "sunscreen for chlorine" because of its protective effect against UV degradation.
The recommended CYA range depends on your pool type and chlorination method:
The rule of thumb for granular cyanuric acid is:
13 oz of CYA raises 10 PPM in 10,000 gallons
The exact formula is: Ounces = (PPM increase × Pool gallons × 0.00013)
For a 15,000-gallon pool needing a 20 PPM increase: (20 × 15,000 × 0.00013) = 39 oz (about 2.4 lbs)
CYA affects how much free chlorine you need to maintain proper sanitation. The CDC recommends maintaining a chlorine-to-CYA ratio:
Higher CYA requires higher chlorine levels to maintain the same sanitizing power.
Too much CYA can cause significant problems:
Keep CYA below 100 PPM for traditional pools and below 80 PPM for saltwater pools.
Unlike other chemicals, CYA is very stable and doesn't break down on its own. To lower CYA:
Example: To lower from 100 PPM to 40 PPM, drain 60% of the pool and refill.
Regular use of stabilized chlorine causes CYA to build up over time. Consider switching to unstabilized chlorine (liquid or cal-hypo) once CYA reaches target levels.
It depends on your pool volume and current CYA level. As a rule of thumb, 13 oz of granular CYA raises 10 PPM in 10,000 gallons. Use the calculator above for your specific situation.
Yes. Stabilizer, conditioner, and cyanuric acid (CYA) are all the same chemical compound. Different brands use different names, but they're all protecting chlorine from UV degradation.
Granular CYA can take 48-72 hours to fully dissolve, especially in cooler water. Pre-dissolving in warm water or using a sock speeds up the process. Wait at least 48 hours before retesting.
Yes, and it's a common problem. CYA above 100 PPM can make chlorine less effective at sanitizing. The only way to lower CYA is to partially drain and refill the pool.
Trichlor tablets and dichlor shock contain stabilizer. Each time you use them, CYA increases. Switch to unstabilized chlorine (liquid chlorine or calcium hypochlorite) once CYA is adequate.
Usually not, or very minimal amounts. Without UV exposure, chlorine lasts much longer. Indoor pools typically maintain 0-20 PPM CYA at most.
CYA is slightly acidic, so large additions may temporarily lower pH. More significantly, CYA contributes to total alkalinity readings but not to actual alkalinity buffering, which can confuse test results.
Only when levels drop below your target range. CYA is very stable and only decreases through splash-out, backwashing, or dilution. Most pools only need CYA added at the start of the season.
Granular CYA is pure (99%+) and most economical. Liquid stabilizer is pre-dissolved (30-35% concentration) and easier to add but more expensive per unit of CYA.
It's not recommended. Using trichlor or dichlor when CYA is already adequate will push levels higher over time. Switch to liquid chlorine or calcium hypochlorite for regular chlorination.
Amount of granular CYA needed to raise 10 PPM:
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