How to raise CYA in a pool: add stabilizer the right way
Low CYA means your chlorine has no UV protection. In direct summer sun, a pool with no stabilizer can lose most of its free chlorine within a few hours — leaving it unsanitized during the exact hours when bather load is highest. At season start, or after a large drain-and-refill, getting CYA back to target range is one of the first things to do before the pool is ready to swim.
What product to buy
Look for any of these at a pool supply store or home improvement store:
- Pool stabilizer (granular) — the most common name
- Pool conditioner (granular) — same product, different label
- Cyanuric acid — the chemical name, sometimes listed on the label
All three are the same compound. Buy the granular form. Liquid CYA products exist but are less common, more expensive, and offer no practical advantage. Check the active ingredient on the label — it should list cyanuric acid at 98–100% concentration. Avoid products that bundle CYA with algaecide or other chemicals; they make dosing harder to control.
How much to add
Approximately 13 oz (0.8 lbs) per 10,000 gallons raises CYA by 10 ppm when using pool-grade granular cyanuric acid. Use the table below for common pool sizes, or the formula at the bottom.
| Target CYA increase | 10,000 gal pool | 15,000 gal pool | 20,000 gal pool | 25,000 gal pool |
|---|---|---|---|---|
| +10 ppm | 13 oz | 20 oz | 26 oz | 33 oz |
| +20 ppm | 26 oz (1.6 lb) | 39 oz (2.4 lb) | 52 oz (3.3 lb) | 65 oz (4.1 lb) |
| +30 ppm | 39 oz (2.4 lb) | 59 oz (3.7 lb) | 78 oz (4.9 lb) | 98 oz (6.1 lb) |
| +40 ppm | 52 oz (3.3 lb) | 78 oz (4.9 lb) | 104 oz (6.5 lb) | 130 oz (8.1 lb) |
If your pool volume is not in the table, use: oz to add = (target increase in ppm × pool gallons) ÷ 7,500. For example, raising CYA by 25 ppm in an 18,000-gallon pool: (25 × 18,000) ÷ 7,500 = 60 oz (3.75 lbs).
Add in increments — don't overshoot
CYA test accuracy is only ±10 ppm, so there's no point trying to hit 40 ppm exactly. Aim for the middle of your target range (35 ppm if targeting 30–40). More importantly: if you overshoot, the only fix is a partial drain. Add conservatively, wait 48 hours, retest, then add more if needed.
How to add CYA correctly
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Pre-dissolve in warm water (recommended) Fill a 5-gallon bucket with warm tap water. Pour in the measured granules and stir until dissolved — this may take 5–10 minutes. CYA dissolves faster in warm water. Once dissolved, pour slowly around the perimeter of the pool near the return jets with the pump running.
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Alternative: the sock method Place the measured granules in a clean mesh bag or old sock. Hang it near a return jet so the returning water flows through the bag. Squeeze the bag occasionally to break up clumps. Leave it in place until the granules are fully dissolved (typically 24–48 hours). This works well for large doses that don't dissolve quickly in a bucket.
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Run the pump continuously Keep the pump running for at least 24–48 hours after adding CYA. Good circulation is required for even distribution and full dissolution. Do not turn the pump off and on during this period.
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Wait before retesting CYA dissolves significantly more slowly than most pool chemicals. Testing after 6 or 12 hours will give a falsely low reading. Wait a full 24–48 hours and confirm the granules are completely dissolved before retesting. If the test still seems low, wait another 24 hours before adding more.
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Retest and add more if needed If CYA is still below target after 48 hours, calculate and add the remaining dose. CYA does not affect pH or alkalinity, so no other adjustments are needed after adding it.
Using trichlor tablets to raise CYA
If you're opening the pool for the season with CYA near zero, running trichlor tablets for the first week or two is a practical way to raise CYA while simultaneously chlorinating. Each tablet dissolves into both chlorine and cyanuric acid.
This is intentional and common at season startup. Once CYA reaches your target range (30–50 ppm for regular pools), switch to liquid chlorine for daily chlorination. Continuing with tablets after CYA is at target will push CYA above range over the season, eventually requiring a partial drain.
When trichlor tablets make sense
Season startup with CYA near 0: tablets raise CYA and chlorinate simultaneously. After draining to lower CYA: you've drained CYA out, and tablets can bring it back up while also restoring chlorine. Any other time: if CYA is already at 30–50 ppm, tablets will push it higher — use liquid chlorine instead and add granular stabilizer directly if a top-up is needed.
What target CYA to aim for
| Pool Type | Target CYA | Notes |
|---|---|---|
| Regular chlorine pool | 30–50 ppm | Lower end (30–40) keeps FC minimums easier to maintain |
| Saltwater / SWG pool | 60–80 ppm | Higher CYA extends the cell's output between generation cycles |
| Indoor pool | 0–20 ppm | No UV exposure; CYA's FC-raising effect isn't worth the tradeoff |
For regular pools, aim for 30–40 ppm rather than 50. At 30–40, your FC minimum is about 2.25–3 ppm, which is easy to maintain. At 50, the minimum is 3.75 ppm — workable, but leaves less room for error. At 40 ppm CYA the shock level is 16 ppm; at 50 it's 20 ppm. Staying at the low end of the range means easier management all season.
SWG pools run higher because the salt cell generates chlorine continuously — higher CYA helps that chlorine last longer between production cycles. The SWG minimum is CYA × 5% (vs. 7.5% for regular pools), which compensates for the higher CYA. See the FC/CYA chart for exact minimums at every level.
What happens after adding CYA
CYA does not affect pH or total alkalinity, so no other chemistry changes are needed after adding it. Your FC target will change once CYA rises — the minimum FC is approximately CYA × 7.5%, so make sure to adjust your dosing upward as CYA increases.
For example: if you're starting the season with CYA at 10 ppm and targeting 40 ppm, you may have been maintaining FC at 2 ppm. Once CYA reaches 40, your minimum FC is 3 ppm and your target range rises to 4–6 ppm. Add more chlorine immediately after CYA hits range — don't wait until you see FC drop first.
What not to do
- Don't add directly to the skimmer basket. Undissolved granules in the plumbing can damage the pump. Always pre-dissolve or use the sock method.
- Don't retest too soon. CYA takes 24–48 hours to fully dissolve and circulate. Testing at 4 hours will show a falsely low result and lead to over-dosing.
- Don't add more than needed to overshoot. There's no chemical fix for high CYA — the only way down is a partial drain.
- Don't keep using trichlor tablets after CYA is at target. Each tablet adds more CYA. Switch to liquid chlorine once you've hit your range.
Know when CYA is in range — and when it's drifting
PoolChem Tracker logs your CYA over time so you can see when it's rising, when it's hit target, and when it needs attention. FC minimums update automatically with every CYA reading.
Frequently asked questions
How do you raise CYA in a pool?
Add granular cyanuric acid, sold as pool stabilizer or pool conditioner. Pre-dissolve in a bucket of warm water, then pour near a return jet. About 13 oz per 10,000 gallons raises CYA by 10 ppm. Keep the pump running for 24–48 hours before retesting.
How long does CYA take to dissolve?
At least 24–48 hours with continuous pump circulation. CYA dissolves significantly more slowly than most pool chemicals. Testing after a few hours will show a falsely low reading. Wait until you're confident the granules are fully dissolved before retesting. If using the sock method, squeeze the bag occasionally to break up clumps and speed dissolution.
How much stabilizer raises CYA by 10 ppm?
About 13 oz (just under 1 lb) of granular cyanuric acid per 10,000 gallons. For a 15,000-gallon pool: about 20 oz. For 20,000 gallons: about 26 oz. Use the formula: oz to add = (target increase in ppm × pool gallons) ÷ 7,500.
What CYA level should I aim for?
30–50 ppm for regular chlorine pools, 60–80 ppm for saltwater (SWG) pools. Within the regular-pool range, 30–40 is preferable — the FC minimum stays lower, shock levels are more manageable, and there's more room before CYA creeps into problematic territory.
Can I use trichlor tablets to raise CYA?
Yes, and this is a common approach at season startup when CYA is near zero. Trichlor tablets add both chlorine and CYA as they dissolve. Once CYA reaches your target range, switch to liquid chlorine to prevent further accumulation. Don't use tablets as your primary chlorine source once CYA is at target — they'll keep pushing it higher.
Does adding CYA affect pH or alkalinity?
No. Granular cyanuric acid dissolves without significantly changing pH or total alkalinity. No other chemistry adjustments are needed from the CYA addition itself. The only thing that changes is the CYA reading — and subsequently your FC minimum, which will be higher once CYA rises.
CYA / Pool Stabilizer Series
- Pool Stabilizer (CYA) — what it is, ideal levels, and how to manage it (start here)
- Best CYA Level for Liquid Chlorine Pools
- How to Lower CYA in a Pool
- How to Raise CYA in a Pool
- High CYA in a Pool — Causes, Symptoms, and Fixes
- Low CYA in a Pool — Risks and How to Fix It
- How Much Stabilizer to Add to a Pool
- Best CYA Level for Saltwater Pools
Keep reading
- What Is CYA (Pool Stabilizer)? — ideal levels, how CYA builds up, and why it raises your FC minimum
- How to Lower CYA in a Pool — the only method that works: drain and refill
- FC/CYA Chart: Safe Chlorine Levels at Every CYA Value — update your FC target once CYA rises
- Does Liquid Chlorine Raise CYA? — which chlorine types add CYA and which don't
- Chlorine Dose Calculator — dosing recommendations adjust automatically for your new CYA level
- Pool Turned Green Overnight? — often caused by low CYA letting chlorine degrade before algae can be controlled
- How to Balance Pool Water in 4 Steps — where CYA fits in the full balancing sequence