The formula
oz of stabilizer = 0.0013 x gallons x ppm rise
Worked example: a 15,000 gallon pool at 10 ppm with a 40 ppm target needs a 30 ppm rise. 0.0013 x 15,000 x 30 = 58.5 oz, or about 3.7 lb of granular stabilizer. For liquid stabilizer, divide by the label strength (at 32%, multiply by about 3).
Stabilizer dosing table
| Pool size | +10 ppm | +20 ppm | +30 ppm |
|---|---|---|---|
| 5,000 gal | 4.1 lb (65 oz) | 8.1 lb (130 oz) | 12.2 lb (195 oz) |
| 10,000 gal | 8.1 lb (130 oz) | 16.3 lb (260 oz) | 24.4 lb (390 oz) |
| 15,000 gal | 12.2 lb (195 oz) | 24.4 lb (390 oz) | 36.6 lb (585 oz) |
| 20,000 gal | 16.3 lb (260 oz) | 32.5 lb (520 oz) | 48.8 lb (780 oz) |
| 25,000 gal | 20.3 lb (325 oz) | 40.6 lb (650 oz) | 60.9 lb (975 oz) |
| 30,000 gal | 24.4 lb (390 oz) | 48.8 lb (780 oz) | 73.1 lb (1170 oz) |
| 40,000 gal | 32.5 lb (520 oz) | 65.0 lb (1040 oz) | 97.5 lb (1560 oz) |
Print this page for a copy to keep with your chemicals.
Ideal CYA by pool type
| Pool | Target CYA | Why |
|---|---|---|
| Chlorine pool (outdoor) | 30 to 50 ppm | Enough to slow sunlight loss without weakening chlorine. |
| Saltwater pool | 60 to 80 ppm | Cells make chlorine slowly, so they need more protection. |
| Indoor pool | 0 to 30 ppm | No sunlight to protect against. |
| Hot, sunny climate | Top of the range | Strong UV burns chlorine faster. |
Salt pools need 60 to 80 ppm; check the rest of your salt numbers in the salt calculator.
Chlorine levels by CYA
CYA holds part of your chlorine in reserve, so the more CYA you have, the more free chlorine you need. These levels use the widely used ratios: minimum about 7.5% of CYA, target about 11.5%, shock about 40%.
| CYA | Minimum FC | Target FC | Shock FC |
|---|---|---|---|
| 20 ppm | 1.5 ppm | 2.3 ppm | 10 ppm |
| 30 ppm | 2.3 ppm | 3.5 ppm | 12 ppm |
| 40 ppm | 3 ppm | 4.6 ppm | 16 ppm |
| 50 ppm | 3.8 ppm | 5.8 ppm | 20 ppm |
| 60 ppm | 4.5 ppm | 6.9 ppm | 24 ppm |
| 70 ppm | 5.3 ppm | 8.1 ppm | 28 ppm |
| 80 ppm | 6 ppm | 9.2 ppm | 32 ppm |
| 90 ppm | 6.8 ppm | 10.4 ppm | 36 ppm |
| 100 ppm | 7.5 ppm | 11.5 ppm | 40 ppm |
Dose to those numbers with the chlorine calculator.
How to add stabilizer
- Skimmer sock: put the granules in a sock or mesh bag in the skimmer basket or in front of a return.
- Bucket: pre-dissolve in warm water and pour it in front of a return. It takes a while to dissolve.
- Never broadcast granules on a vinyl pool. They settle and can bleach the liner.
- Keep the pump on, wait 48 to 72 hours before retesting, and don't backwash for a week.
Why CYA keeps climbing
Trichlor tablets add about 0.6 ppm CYA for every 1 ppm of chlorine they release, and dichlor about 0.9 ppm. A pool that runs on pucks all summer can gain 30 ppm or more by fall. Evaporation leaves CYA behind, so only fresh water brings it down. If your chlorine won't hold, high CYA is often why; the which calculator wizard walks through it. Read more in what is cyanuric acid and cyanuric acid explained, then check the whole picture with the pool health score.