CYA (Cyanuric Acid) Dose Formula
The Formula
| Symbol | Description | Unit |
|---|---|---|
Target CYA | Desired cyanuric acid level in ppm (outdoor pools: 30–50 ppm; salt pools: 60–80 ppm) | ppm |
Current CYA | Current CYA level measured by test kit | ppm |
Volume | Pool volume in gallons | gallons |
0.000133 | Ounces of CYA per ppm per gallon of pool water | oz/ppm/gal |
Worked Example
Pool: 15,000 gallons. Current CYA: 20 ppm. Target CYA: 40 ppm.
- Increase needed = 40 − 20 = 20 ppm
- Using the rule: 13 oz per 10,000 gal per 10 ppm
- For 20 ppm on 10,000 gal: 13 × 2 = 26 oz
- For 15,000 gal: 26 × 1.5 = 39 oz
Add approximately 39 oz (about 2.4 lbs) of cyanuric acid granules. Place in a nylon sock and hang in front of a return jet, or pre-dissolve in warm water and add. Allow 24–48 hours for full dissolving before retesting.
How This Formula Works
Cyanuric acid (CYA) — also called stabiliser or conditioner — protects chlorine from UV light degradation. Without CYA, outdoor pool chlorine can be destroyed within 30–60 minutes of direct sunlight.
- CYA cannot be removed chemically — only through partial drain and refill.
- CYA accumulates over time when using stabilised chlorine products (trichlor, dichlor). Each pound of trichlor adds about 6 ppm CYA per 10,000 gallons.
- At high CYA levels (above 80 ppm), chlorine effectiveness is significantly reduced — called chlorine lock.
- Equivalent rule: 13 oz of CYA granules raises a 10,000-gallon pool by approximately 10 ppm.
Limitations & Notes
CYA raises slightly more slowly than most other chemicals — 24 to 48 hours for complete dissolution. Do not retest before it has fully dissolved. Granular CYA does not dissolve quickly in the skimmer and can damage equipment — pre-dissolve separately.
Last reviewed: 2026-06-01