How does this pool cyanuric acid calculator work?
This pool cyanuric acid calculator is a free browser tool. The calculator returns the ounces of stabilizer granules needed to raise CYA to a target. The calculator returns the dose in ounces and pounds. The calculator returns a dissolution-time estimate too. CYA is the chemical that shields free chlorine from UV destruction. CYA is also called stabilizer, conditioner, or pool sunscreen. Pool cyanuric acid is the locked-chlorine reservoir that releases sanitizer back into the water.
The ideal CYA band is 30–50 ppm for outdoor pools and 0–20 ppm for indoor pools. According to CDC pool operation guidance, every 10 ppm of CYA roughly doubles chlorine half-life in direct sunlight. 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.
How much stabilizer to raise CYA per 10,000 gallons?
The dose is 13 oz of 99% cyanuric acid granules per 10 ppm CYA raise per 10,000 gallons. A 30 ppm raise in 10,000 gallons needs 39 oz, or 2.4 lb. The same raise in 20,000 gallons needs 78 oz, or 4.9 lb. The same raise in 30,000 gallons needs 117 oz, or 7.3 lb. Granular stabilizer dissolves slowly through the skimmer sock over 4–7 days.
| CYA raise | 10,000 gal — stabilizer | 20,000 gal — stabilizer | 30,000 gal — stabilizer |
|---|---|---|---|
| 10 ppm | 13 oz (0.8 lb) | 26 oz (1.6 lb) | 39 oz (2.4 lb) |
| 20 ppm | 26 oz (1.6 lb) | 52 oz (3.3 lb) | 78 oz (4.9 lb) |
| 30 ppm | 39 oz (2.4 lb) | 78 oz (4.9 lb) | 117 oz (7.3 lb) |
| 40 ppm | 52 oz (3.3 lb) | 104 oz (6.5 lb) | 156 oz (9.8 lb) |
What raises CYA, knowingly or not?
- Granular stabilizer is pure cyanuric acid; the direct route.
- Trichlor tablets add 9–10 ppm CYA per 1 ppm chlorine; major source of CYA creep.
- Dichlor shock adds 9 ppm CYA per 1 ppm chlorine; never use long term.
- Liquid chlorine and cal-hypo add zero CYA; the only no-CYA options.
Why is CYA hard to lower?
CYA does not break down in pool water. CYA is removed only by partial drain or by reverse osmosis. The standard formula is replace X% of pool water to reduce CYA by X%. A 50% drain drops CYA from 80 ppm to 40 ppm. Research published in the Water Quality & Health Council bulletins shows that no chemical product safely destroys CYA in residential pools; the "CYA reducer" products on the market have a 60% success rate at best.
How long does stabilizer take to dissolve?
The dissolve time is 4–7 days. Cyanuric acid is the slowest-dissolving common pool chemical. The calculator returns a stabilizer add of 13 oz per 10 ppm per 10,000 gallons, delivered through the skimmer sock. Run the pump 24 hours a day for the first 3 days after adding. Use the chlorine calculator to keep free chlorine above 7.5% of CYA during dissolution.