Introduction
Noticed your chlorine isn’t working as well even though your levels are fine? The problem could be high cyanuric acid (CYA). In this guide, you’ll learn how to fix high cyanuric acid in your pool with simple, effective steps. Whether you’re dealing with cloudy water, low chlorine performance, or algae despite adding sanitizer, managing CYA levels is key to restoring balance and clarity.
Why Cyanuric Acid Matters for Your Pool
Cyanuric acid—often called “pool stabilizer” or “conditioner”—helps protect chlorine from breaking down in sunlight. It’s essential in outdoor pools. But too much CYA becomes a problem. Here’s why:
- Ideal CYA range: 30–50 ppm (saltwater pools: 60–80 ppm)
- At levels over 100 ppm, CYA binds to chlorine too tightly, reducing its ability to sanitize
- Chlorine lock can occur, where free chlorine is present but ineffective
- Algae blooms and cloudy water become more likely
- You’ll end up wasting money on extra chlorine trying to compensate
Maintaining proper CYA levels keeps chlorine active, water clear, and your pool safe.
Step-by-Step Guide to Fix High Cyanuric Acid
Step 1: Test the CYA Level Accurately
Use a reliable liquid test kit specifically for CYA. Test strips often give vague or inconsistent readings.
- Fill the CYA test cylinder to the appropriate line
- Add the CYA reagent and mix as instructed
- Pour into the view tube and look down from above
- Stop when the black dot disappears—this is your CYA level
💡 Tip: Test mid-morning for consistent sunlight conditions.
If your level is above 100 ppm, action is required.
Step 2: Determine How Much Water to Replace
There’s no chemical to lower CYA directly. The only solution is water dilution. That means draining and refilling a portion of your pool.
Use this guide:
- 50% drain = roughly 50% CYA reduction
- 25% drain = roughly 25% CYA reduction
Example:
If your CYA is 120 ppm and you want to reduce it to 60 ppm, you’ll need to drain and refill 50% of your pool water.
⚠️ Caution: Check your local water restrictions before draining large volumes.
Step 3: Partially Drain the Pool
You can drain:
- From the top using a submersible pump
- From the bottom using the “waste” setting on your filter
- Manually with a siphon hose for small pools
Drain slowly to prevent pool structure damage, especially in fiberglass or vinyl pools. Avoid fully draining unless absolutely necessary.
💡 Tip: Mark the water line before draining so you know exactly how much you removed.
Step 4: Refill with Fresh Water
Refill the pool with fresh tap water or well water until the original water level is restored. Do not use water from another pool or body of water.
- Turn on your pump to circulate the water for at least 4–6 hours
- Allow water to fully mix before retesting CYA levels
💧 Be prepared to rebalance pH, chlorine, and alkalinity after refill.
Step 5: Retest and Adjust as Needed
After circulation:
- Retest your cyanuric acid level
- Retest chlorine, pH, and alkalinity
Make adjustments to chlorine and pH if necessary to ensure water is safe for swimming.
If CYA is still slightly high, you can perform another partial drain to bring it within the ideal range.
Common Mistakes to Avoid
1. Adding More Stabilized Chlorine
Stabilized chlorine products like trichlor and dichlor contain cyanuric acid. Continued use will drive CYA up over time.
✅ Switch to liquid chlorine (sodium hypochlorite) or calcium hypochlorite if your CYA is already high.
2. Not Testing Often Enough
CYA can creep up without warning if you regularly use stabilized chlorine.
✅ Test CYA at least once a month, more often in summer.
3. Ignoring High CYA
If you leave CYA too high, you risk chlorine lock, algae, and cloudy water—plus wasted money on chlorine that doesn’t work.
✅ Fix high CYA promptly with dilution methods.
4. Draining Too Much Too Fast
Fully draining a pool can damage the liner or structure, especially in high groundwater areas.
✅ Stick to safe partial drains (25–50%) unless supervised by a professional.
5. Refilling with Treated Water
Avoid water sources with added stabilizers or high TDS (total dissolved solids).
✅ Use clean, untreated municipal or well water whenever possible.
Extra Tips & Pool Hacks
- Use a CYA reducer product cautiously. Some claim to lower CYA, but results vary and can interfere with other water chemistry. Drain and refill is still the most effective method.
- Track chlorine use. If you regularly use pucks or tablets, monitor CYA levels monthly and alternate with unstabilized chlorine.
- Install a rainwater diverter. In wet climates, capturing and directing rainwater into your pool can help dilute slowly over time.
- Set reminders to test. Keeping a monthly testing schedule avoids surprises and maintains better overall balance.
🧪 Related Tip: [Read our guide on how to maintain pool water clarity] to prevent cloudy issues caused by high CYA levels.
Conclusion
Fixing high cyanuric acid in your pool isn’t difficult—it just takes the right approach. With accurate testing, a planned partial drain, and a smart chemical routine going forward, you’ll keep CYA levels under control and ensure your chlorine works effectively. Take care of it now and enjoy a safe, clean, and balanced pool all summer long.
👉 Bookmark this guide and use it whenever CYA levels creep too high.