Is cyanuric acid the same as chlorine stabilizer?

Yes. Stabilizer, conditioner, pool sunscreen, and CYA are all the same chemical. The trade name varies by brand.

How much does cyanuric acid cost?

Granular stabilizer runs $4–$7 per pound in 2025. A 5-pound bag treats a 20,000-gallon pool from 20 to 50 ppm. Trichlor tablets cost more per ppm of CYA delivered.

Can I use trichlor without raising CYA?

No. Trichlor tablets always release cyanuric acid. Use trichlor only as a top-up source, not a primary sanitizer, once CYA reaches 50 ppm.

Why does my CYA never seem to go down?

CYA only drops with water replacement. A 25% drain drops CYA by 25%. Plan a partial drain every 3–5 years to manage CYA creep.

What Is Cyanuric Acid in a Pool? Stabilizer Function, ppm, and Removal

Cyanuric acid targets
Outdoor ideal	30–50 ppm
Indoor ideal	0–20 ppm
Action threshold (high)	100 ppm — drain
Granular dose	13 oz per 10 ppm per 10,000 gal
Trichlor CYA add	~0.6 ppm per 1 ppm chlorine

What is cyanuric acid in pool water?

Cyanuric acid is the chemical that shields free chlorine from UV destruction. Cyanuric acid is also called CYA, stabilizer, conditioner, or pool sunscreen. Cyanuric acid is granular, off-white, and slow to dissolve. Pool cyanuric acid is the locked-chlorine reservoir that releases sanitizer back into the water on demand. Pool cyanuric acid extends free chlorine half-life by 8–10× in summer sun.

According to CDC pool operation guidance, the ideal CYA band is 30–50 ppm for outdoor pools. Research from the Pool & Hot Tub Alliance shows that pools at 0 ppm CYA lose 90% of free chlorine in 2 hours of summer sun. Pools at 40 ppm CYA lose only 25% in the same window.

Diagram of pool water chemistry showing free chlorine, pH, total alkalinity, cyanuric acid, and calcium hardness as five connected dials. — Five interacting water-balance parameters. Move one and the others shift in response.

Step-by-step dosing flow: test water, enter readings, pick target, read calculated dose, add chemical, retest in 6 hours. — Standard dosing flow followed by every calculator on this site.

Reference band chart with ideal ranges: free chlorine 1 to 4 ppm, pH 7.4 to 7.6, alkalinity 80 to 120 ppm, CYA 30 to 50 ppm, calcium 200 to 400 ppm. — Target ranges this calculator uses by default. Override them in the form if your local code differs.

How is cyanuric acid measured?

The test is turbidity-based. The reagent forms a cloudy precipitate proportional to CYA. The cloudier the sample, the higher the reading. Test strips give a rough range only. Research from the Pool & Hot Tub Alliance shows that turbidity readings carry ±10 ppm accuracy at typical residential ranges.

CYA reading	Pool type	Status
0–10 ppm	Indoor	Acceptable
0–10 ppm	Outdoor	Too low; chlorine burns off
30–50 ppm	Outdoor	Ideal
60–80 ppm	Any	High; chlorine locked
>100 ppm	Any	Drain required

What raises CYA — even unintentionally?

Granular stabilizer — direct add; 13 oz per 10 ppm per 10,000 gal.
Trichlor tablets — every 1 ppm chlorine adds about 0.6 ppm CYA.
Dichlor shock — every 1 ppm chlorine adds about 0.9 ppm CYA.
Refill water — usually 0 ppm CYA unless from a tested municipal source.

Why is high CYA hard to fix?

Cyanuric acid does not break down. CYA does not react with chlorine. CYA does not evaporate. The only ways to lower CYA are partial drain and reverse osmosis service. According to research published in the Water Quality & Health Council bulletins, "CYA reducer" products show inconsistent results in residential pools; the standard fix is a percent drain matching the percent reduction wanted. Use the CYA calculator to compute the dose to add — or the drain percent if the level is already too high.

Do indoor pools need CYA?

No. Indoor pools have no UV source. CYA only adds the lock penalty with no benefit. Hold indoor CYA at 0–20 ppm and dose chlorine without stabilizer.

What Is Cyanuric Acid: Stabilizer Function, ppm Range, and Removal Path

Quick reference card