Pool Stabilizer: What It’s and Exactly How Much to Add
Stabilizer, typically cyanuric acid (CYA), safeguards free chlorine from UV degradation in pools exposed to sunlight. Aim for 30 to 50 parts per million (ppm) for outdoor chlorinated pools and between 60 and 90 ppm for saltwater or SWG systems. To boost CYA by 10 ppm, you’d add roughly 1 pound of granular stabilizer per every 4,000 gallons of pool water. In the absence of any stabilizer, expect your chlorine to dissipate between 50 and 90 percent within two hours under direct sunlight. At a CYA level of 30 ppm, that same amount lasts around seven hours.
For a comprehensive guide to all aspects of pool chemistry, including other essential parameters like pH, alkalinity, and calcium hardness, refer to our complete pool chemistry guide.
What is pool stabilizer?
Pool stabilizer, cyanuric acid, and pool conditioner are the same product, three names for one chemical. CYA forms a weak, temporary bond with free chlorine that shields it from UV radiation. When UV light hits the bond, it breaks down without consuming the chlorine itself, so your FC stays in the water longer.
Don’t skip this.
A few key points to understand upfront:
- CYA doesn’t change how much chlorine you add. It makes the chlorine you already have last longer.
- Without CYA, 50% of free chlorine is lost within 35 minutes of direct sunlight (TroubleFreePool data).
- With 30 ppm CYA: 50% FC loss takes 7 hours instead.
- Pentair confirms that UV alone destroys unstabilized chlorine within 45 minutes.
See CDC chlorine disinfection standards for background on why UV resistance matters in outdoor pool sanitation.
Video: “How To Balance CYANURIC ACID” by Swim University
Do you actually need pool stabilizer?
You do need it if:
- You have an outdoor chlorine pool and have never added stabilizer
- Chlorine keeps disappearing within 24 hours despite correct pH and regular dosing
- You’re filling a new pool for the first time
- Your current CYA level is below 20 ppm
You don’t need it if:
- You have an indoor pool with no UV exposure
- Your CYA is already testing at 50+ ppm for a standard pool
- You have a saltwater pool, add when CYA drops below 60 ppm
Pay attention.
Often overlooked.
Worth checking.
If you use chlorine tablets exclusively, your CYA is probably rising whether you add stabilizer or not. This is one of the most common sources of “chlorine not holding” problems, the CYA has climbed so high that chlorine becomes ineffective. See our cyanuric acid levels and adjustment guide for how to diagnose this.
Target CYA levels for different pool types
| Pool Type | CYA Target | Notes |
|---|---|---|
| Standard outdoor chlorine | 30-50 ppm (ideal: 40 ppm) | Test monthly |
| Saltwater / SWG pool | 60-90 ppm | SWGs need more UV protection |
| Indoor pool | 0-20 ppm | Minimal sun exposure. Low stabilizer fine |
CYA isn’t consumed by normal pool use. It only leaves your pool through draining, splash-out, or backwashing the filter. This means it accumulates over time, especially if you use stabilized chlorine tablets.
The FC/CYA relationship matters a great deal for proper sanitation. At 50 ppm CYA, you must maintain a minimum of 4 ppm free chlorine. At 30 ppm CYA, 2 ppm FC is sufficient. Above 100 ppm CYA, the chlorine that’s required to sanitize becomes impractically high. Leslie’s recommends draining when CYA exceeds 100 ppm. TFP notes that at above 90 ppm CYA, the SLAM process becomes very difficult because SLAM-level FC doses become enormous.
Here’s the TFP minimum FC table by CYA level. We recommend bookmarking this:
Don’t skip this.
| CYA level | Minimum FC | SLAM FC level |
|---|---|---|
| 20 ppm | 2 ppm | 12 ppm |
| 30 ppm | 2 ppm | 12 ppm |
| 40 ppm | 3 ppm | 16 ppm |
| 50 ppm | 4 ppm | 20 ppm |
| 60 ppm | 5 ppm | 24 ppm |
| 70 ppm | 6 ppm | 28 ppm |
| 80 ppm | 7 ppm | 31 ppm |
| 90 ppm | 8 ppm | 35 ppm |
See the full TroubleFreePool FC/CYA minimum chart for the complete reference.
How much pool stabilizer to add (dosing table)
The standard dosing rate for pool stabilizer is 1 lb of granular cyanuric acid per 4,000 gallons to raise CYA by 10 ppm.
Skip it.
Use this table to find your dose:
| Target increase | 10,000 gal | 15,000 gal | 20,000 gal |
|---|---|---|---|
| +10 ppm | 2.5 lbs | 3.75 lbs | 5 lbs |
| +20 ppm | 5 lbs | 7.5 lbs | 10 lbs |
| +30 ppm | 7.5 lbs | 11.25 lbs | 15 lbs |
Example: 15,000 gallon pool currently at 10 ppm CYA that needs to reach 40 ppm: add approximately 11.25 lbs of granular stabilizer in two rounds (7.5 lbs first, retest after 48 hours, then adjust).
Don’t add more than 30 ppm worth at one time. CYA absorbs slowly and takes 24-48 hours to fully register on a test kit. Adding more before it registers is how pools end up over-stabilized.
Step-by-step: how to add pool stabilizer safely
What you need: measuring scale, 5-gallon bucket, warm water, chemical-resistant gloves
Test your CYA level with liquid kits or through a pool store. Skipping this step can lead to issues. If your current CYA stands at 50 ppm, adding more stabilizer will likely worsen your situation. Use the provided table for dosage calculations. An increase of 10 ppm calls for roughly 3 lbs of stabilizer in a 12,000-gallon pool. Mix 3 to 4 pounds of granular CYA with warm water in a 5-gallon bucket, stirring until dissolved, refer to EPA guidelines for safe handling instructions.
Pour the solution through your skimmer while ensuring the pump is running. Avoid direct pool pour to prevent liner damage or floor deposits. Run the pump continuously for 24-48 hours without backwashing, as filtering could flush out your new CYA before it stabilizes. Retest after 48 hours; if levels remain low, apply a second partial dose and reapply these steps.
Safety note: CYA is a mild eye and skin irritant. Wear gloves and avoid inhaling dust from the granules. The AAA rule applies: Always Add Acid (or any concentrated chemical) to water, never water to the chemical. For muriatic acid used alongside this process, see our guide on muriatic acid for pH adjustment.
For balancing alkalinity as part of your overall chemistry adjustment, see how to raise pool alkalinity.
What if CYA is too high?
CYA can’t be removed chemically. The only fix is dilution through partial draining and refilling.
- Drain 25%: Reduces CYA proportionally. A pool at 100 ppm CYA drops to approximately 75 ppm after a 25% drain-refill.
- Drain 50%: More aggressive. A 15,000 gallon pool at 120 ppm CYA drops to approximately 60 ppm after draining and refilling 7,500 gallons.
When to drain: Leslie’s recommends draining when CYA exceeds 100 ppm. TFP says above 90 ppm, the SLAM process becomes so demanding (requiring SLAM-level FC at 35+ ppm) that it’s usually easier to drain.
Prevention is straightforward: if you use tablets as your primary chlorine source, test CYA monthly and switch to liquid chlorine when levels approach 70-80 ppm. Liquid chlorine adds no CYA, which gives you a way to chlorinate without accelerating stabilizer buildup.
How we wrote this guide
PoolCareHelp doesn’t republish pool-store talking points. Each guide is cross-referenced against primary chemistry and equipment sources before publishing. For this article we consulted:
- TroubleFreePool CYA chart and FC:CYA ratio table, source for the 30-50 ppm outdoor and 60-90 ppm SWG ranges
- Taylor Technologies K-2006 CYA test method, source for the turbidity-based CYA test procedure
- Pentair UV protection documentation, source for the 50%-loss-in-35-minutes unstabilized timing
Editorial decisions we made for this guide:
- We recommend 30-50 ppm CYA for outdoor liquid-chlorine pools (TFP range) and 60-90 ppm for SWG/saltwater because higher CYA is needed to offset salt-cell chlorine generation
- We caution against trichlor tablets as the primary chlorine source long-term because they raise CYA by ~6 ppm per ppm of FC added, most CYA-too-high cases trace back to trichlor
- We name dilution (partial drain-and-refill) as the only fix for high CYA because no chemical reliably removes it, claims to the contrary in retailer-aligned content don’t hold up
Last reviewed by Tom Hill on 2026-05-28. If you find an error or a newer source we should reference, see About for how we issue corrections.
FAQ
What is the difference between pool stabilizer and cyanuric acid?
Cyanuric acid, or CYA, is stabilizer, conditioners, and conditioners in a single role, pool stabilizers. You’ll find these terms interchanged on product labels and in maintenance guides. Know them all for accurate identification and use.
How long does it take for pool stabilizer to work?
CYA takes 24-48 hours to fully dissolve and register in pool water. You may see a partial reading after 24 hours, but wait the full 48 hours before testing and deciding whether to add more. Running the pump continuously during this period helps the stabilizer disperse evenly.
Can I add pool stabilizer and chlorine at the same time?
We recommend adding them separately with at least 15-30 minutes between additions and the pump running the whole time. Adding both simultaneously isn’t dangerous. But the CYA needs time to disperse before the chlorine reading stabilizes. Test chlorine 24 hours after adding stabilizer, not immediately.
What happens if I add too much pool stabilizer?
High CYA (above 100 ppm) reduces chlorine effectiveness significantly, the condition pool stores call “chlorine lock.” At very high CYA levels, you may need impossibly high FC doses to maintain proper sanitation. The only fix is partial draining. There’s no chemical that removes CYA. For hot tub owners facing sanitizer questions, see our hot tub chemical balancing and hot tub sanitizer options guides.
Do I need pool stabilizer for an indoor pool?
No. Indoor pools receive no direct UV exposure, so chlorine degrades much more slowly. CYA at 0-20 ppm is fine for indoor pools. Adding stabilizer to an indoor pool is unnecessary and can create the same high-CYA problems described above without any benefit.