Pool Stabilizer (CYA) Calculator
How much granular stabilizer to add for your type of pool, or how much water to replace if it's already too high.
Why our numbers are more realistic
Stabilizer shields chlorine from sunlight, but it also sets how much chlorine you need, and only draining brings it down. Many calculators give the dose and stop there.
| Typical calculator | This calculator | Why it matters |
|---|---|---|
| One 30–50 ppm range for every pool | 30–50 ppm for chlorine pools; for salt pools, your choice of the generator manuals' range or Trouble Free Pool's | Advice for salt pools splits: Trouble Free Pool recommends 70–80 ppm, while the generator manuals we checked ask for 30–50 or 50–75. One range can't fit both. |
| Doesn't say what stabilizer does to chlorine | Shows the chlorine range your target sets | The more stabilizer, the more chlorine you need. In a chlorine pool above 50 ppm CYA, the minimum passes the 4 ppm swim limit on chlorine labels. |
| Gives the full dose and says retest | At most about 30 ppm at a time, with a 3–5 day wait before retesting | Granular stabilizer dissolves slowly. Stabilizer labels we found (through retailer listings) say to wait 3–5 days, because testing early may read low and adding more on that reading could overshoot. The only way back down is draining. |
| Has nothing to say when CYA is already high | Gives the share of water to replace | No practical chemical removes stabilizer, so draining is the fix, and the useful answer is how much water to replace. Going from 80 to 40 ppm means replacing half. |
How this works
Ounces of granular stabilizer = (target ppm − current ppm) ÷ 10 × 13.35 × (gallons ÷ 10,000).
- 13.35 oz per 10 ppm per 10,000 gallons comes from the chemistry (0.834 lb). Pentair's chart works out to about 13 oz.
- Targets: 40 ppm for pools on liquid chlorine, bleach, or tablets. We use 30–50 because it keeps the chlorine you need under the 4 ppm label limit (Trouble Free Pool lists 30–60, ideal 40–50). Salt pools default to 40 on the generator manuals' basis, or 70 on Trouble Free Pool's (60–90 acceptable). The aim point in each range is our choice.
- Chlorine range: from Trouble Free Pool's chlorine/CYA chart, up to the 4 ppm label limit. Salt pools use Trouble Free Pool's salt-pool minimums above 50 ppm CYA (the chart's rows start at 60 and readings from 51 round up to it), so the minimum steps from 4 ppm at 50 to 3 ppm at 51. At 50 or below we use the regular chart, which asks for a little more chlorine.
- Too high: share of water to replace = 1 − target ÷ current.
Common questions
What should CYA be in a salt water pool?
It depends on whose advice you follow. Generator manuals vary: we found 30–50 ppm in the Hayward, Pentair, and Jandy Ei manuals and 50–75 ppm in Jandy's AquaPure 700/1400 manual. Trouble Free Pool recommends 70–80 ppm ideal (60–90 acceptable). The calculator defaults to the manuals; choose the Trouble Free Pool basis to aim for 70. If your warranty depends on your manual's number, follow it.
How do I lower stabilizer in my pool?
Replace water; there's no practical chemical fix. Enter your reading and the calculator gives the share of water to replace. In a salt pool, salt drops by the same share, so top it back up afterward.
How does CYA change how much chlorine I need?
The more stabilizer, the more chlorine it takes to keep the water sanitary. On Trouble Free Pool's chart, 30 ppm CYA needs at least 2 ppm chlorine, 40 needs 3, and 50 needs 4. Salt-generator pools have lower minimums above 50 ppm (3 ppm at 60–70). The pool chlorine calculator, set to your pool type, gives your swim range and dose.
Why does my stabilizer keep going up?
Chlorine tablets (trichlor) and dichlor add stabilizer every time you use them, and it builds up over a season. Test CYA every few weeks if you use them.
Safety
- Add chemicals to water, never water to chemicals. Never mix pool chemicals with each other.
- Follow the product label. It overrides any calculator.
- Keep chemicals away from children, and don't add them just before people swim.
- Public pools: the CDC's Model Aquatic Health Code calls for immediate remediation at 300 ppm CYA or higher. Your state's rules may set a lower limit.
After you add it: order, waits and test limits
Order. Adjusting more than one thing? Do alkalinity first, then pH, then chlorine, with the pump running and at least 20 minutes between, retesting as you go. Keep calcium several hours apart from baking soda or soda ash, since together they can cloud the water. Never pour acid and chlorine in together.
| What you added | Retest after | Good to know |
|---|---|---|
| Liquid chlorine or bleach | About 30 minutes, pump on | Swim once a retest reads 4 ppm or below. |
| Cal-hypo shock | About 30 minutes for chlorine | Wait 24 hours before adjusting pH or alkalinity. Swim once a retest reads 4 ppm or below. |
| Acid (muriatic or dry) | 30 minutes to 2 hours, then the next day | pH creeps back up for a day as the water gives off carbon dioxide. Swim once a retest reads between 7.2 and 7.8. |
| Soda ash (pH up) | About 2 hours | Raises alkalinity too. |
| Baking soda | 6 to 24 hours | Run the pump at least 6 hours first. |
| Calcium chloride | 4 to 8 hours of pump time | Recheck chlorine too. |
| Salt | 24 hours, pump on | Brush the bottom so it dissolves. |
| Stabilizer (CYA) | 3 to 5 days | Don’t backwash for 48 to 72 hours. |
The short waits need the pump running; retesting the next day catches slow drift.
What your test can’t tell you.
- Most pH tests read only 6.8 to 8.2, so a reading at either end may be further out.
- Chlorine above about 10 ppm throws off the pH test and can bleach a chlorine drop test to a false low. Color-match DPD chlorine tests read only to about 5 ppm; an FAS-DPD drop test reads higher.
- Many kits can’t read stabilizer below about 20 ppm.
- Salt generator displays can be off by about 500 ppm; check with a salt test.
- Test strips read calcium only roughly; use a drop kit.
After heavy rain or an overflow, test free chlorine, pH, alkalinity and stabilizer before adding anything. Rain dilutes the water and can move pH either way, so test rather than guess. Strong sun and heat burn chlorine off faster, so in a hot, sunny climate test chlorine daily.
Filling from a well? Test the fill water at the spigot for metals first. Above about 0.2 ppm copper or 0.3 ppm iron, chlorine can turn the metals into stains. Add a metal sequestrant before you chlorinate, wait 3 to 4 days before shocking, and avoid copper-based algaecides.
From: Swim University on chemical order, Trouble Free Pool on adding chemicals, Trouble Free Pool on pH, Taylor Technologies FAQ, Swim University on metals and Trouble Free Pool on metals, plus the product labels and manuals in Sources.
What this doesn't cover
- Liquid stabilizer. It's an option if you'd rather not wait for granular to dissolve, but strengths vary by brand and we couldn't verify a standard dose, so follow its label.
- Indoor pools.
- Commercial and public pools, which follow your state's health code.
Sources
- Taylor Technologies, how and when to use dilutions: mix pool water 1:1 with stabilizer-free water and double the result.
- Trouble Free Pool recommended levels: CYA 30–60 (ideal 40–50) for liquid chlorine, 70–80 ideal (60–90 acceptable) for salt pools. We narrow the chlorine-pool range to 30–50 because of the 4 ppm label limit.
- Trouble Free Pool chlorine/CYA chart: minimum chlorine for each stabilizer level.
- Pentair IntelliChlor manual (Rev P, 2017): stabilizer chart (3.25 lb raises 10,000 gallons from 0 to 40 ppm); CYA 30–50.
- Jandy AquaPure 700/1400 manual: CYA 50–75 ppm.
- EPA-registered label 5185-238: no swimming above 4 ppm chlorine.
- CDC Model Aquatic Health Code: CYA at 300 ppm or higher requires immediate remediation.
Numbers last reviewed: October 9, 2026.