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How Much Stabilizer to Add to a Pool
Stabilizer (cyanuric acid, CYA) shields your chlorine from sunlight so each dose lasts longer.
1 of 3: your gallons
Your dose appears here after the last question.
- 30 to 50 ppm
- chlorine pools
- 70 to 80 ppm
- salt pools
- 13 oz
- raises 10,000 gal by 10 ppm
When figuring out how much stabilizer to add to a pool, plan on roughly 13 oz of cyanuric acid per 10,000 gallons of water for every 10 ppm (parts per million) you want to raise it. Most chlorine pools are happiest somewhere in the 30 to 50 ppm range, while a pool with a salt cell runs better up near 70 to 80 ppm.
- A dose of 13 oz (380 g) will take 10,000 gallons of water up by 10 ppm
- For chlorine pools, aim within the 30 to 50 ppm range
- For salt pools, aim within the 70 to 80 ppm range
- If it climbs too high, only swapping out water brings it back down
Stabilizer is cyanuric acid, which test kits often shorten to CYA (cyanuric acid). Its job is to shield your chlorine from the sun so it doesn't get used up so fast. Test strips and kits give the reading in parts per million (ppm), which simply says how much of the chemical is sitting in your water.
Stabilizer amounts by pool size
Match your pool size to the size of the bump you're after, measured in ppm. Everything here is in US gallons, with amounts rounded to the nearest ounce.
- For 5,000 gallons: use 7 oz to add 10 ppm, 13 oz to add 20 ppm, or 1 lb 4 oz to add 30 ppm
- For 10,000 gallons: use 13 oz to add 10 ppm, 1 lb 11 oz to add 20 ppm, or 2 lb 8 oz to add 30 ppm
- For 15,000 gallons: use 1 lb 4 oz to add 10 ppm, 2 lb 8 oz to add 20 ppm, or 3 lb 12 oz to add 30 ppm
- For 20,000 gallons: use 1 lb 11 oz to add 10 ppm, 3 lb 6 oz to add 20 ppm, or 5 lb to add 30 ppm
- For 25,000 gallons: use 2 lb 2 oz to add 10 ppm, 4 lb 3 oz to add 20 ppm, or 6 lb 5 oz to add 30 ppm
- For 30,000 gallons: use 2 lb 8 oz to add 10 ppm, 5 lb to add 20 ppm, or 7 lb 9 oz to add 30 ppm
- For 40,000 gallons: use 3 lb 6 oz to add 10 ppm, 6 lb 11 oz to add 20 ppm, or 10 lb 1 oz to add 30 ppm
So a 20,000 gallon pool that tests at 20 ppm takes about 1 lb 11 oz to get to 30 ppm.
Finding your pool's gallons
How much product you need comes down to how much water is in the pool. Here are a few common sizes, figuring an average depth around 4.5 feet:
- 12 x 24 ft holds roughly 9,690 gallons
- 16 x 32 ft holds roughly 17,200 gallons
- 20 x 40 ft holds roughly 26,900 gallons
Got a sloped floor? Then your average depth sits midway between the shallow and deep ends. Round and oval shapes carry a bit less water than a rectangle of equal length and width.
Picking the right cyanuric acid level
What level you should aim for depends on how your chlorine gets into the water:
- Liquid chlorine or other added chlorine: 30 to 50 ppm
- A salt cell (the piece of a salt system that turns salt into chlorine): 70 to 80 ppm
The more stabilizer you carry, the more free chlorine you have to keep on hand. Free chlorine is what's still active and able to do the cleaning. Running 30 ppm of stabilizer? Hold free chlorine between 3 and 5 ppm. At 40 ppm, you'll want 4 to 6 ppm.
Putting in stabilizer the safe way
- 1. Get the pump going before you begin, so the water is already circulating when the product goes in.
- 2. Put the product in at a return jet so the outgoing stream pushes it along and around the pool.
- 3. Put in just one chemical at a time, so nothing combines before it has a chance to spread out.
Pool cyanuric acid too high
Stabilizer doesn't wear out or break down, and your filter can't pull it out. Add too much and it just stays put until you remove some water. Going past the target range also means you'll need more free chlorine on hand to keep things clean.
How to lower cyanuric acid in a pool
Fresh water is the only fix. Drain out part of the pool, fill it back up, then test again. How much to swap depends on how far your reading sits from your goal.
| Level now | Goal | Amount to swap |
|---|---|---|
| 60 ppm | 50 ppm | roughly 1 in 6 |
| 80 ppm | 50 ppm | roughly 3 in 8 |
| 100 ppm | 50 ppm | roughly half |
| 100 ppm | 40 ppm | roughly 6 in 10 |
A 20,000 gallon pool sitting at 100 ppm, for instance, calls for about 10,000 gallons of new water to land at 50 ppm.
How this is worked out
Every dose here builds on 380 grams per 10,000 gallons for 10 ppm. From there, the amount grows or shrinks along with your gallons and the ppm you want. Double the pool, double the product.
For gallons, take the surface area in square feet and multiply by the average depth in feet. Multiply that by 7.48, or by 5.9 if your pool is round or oval.
For the share of water to swap, divide your target by where you're at now, then subtract that answer from 1.