Balancing a pool isn't about fixing one number — it's about fixing them in the right order, because each one moves the next. Adjust pH before alkalinity and you'll just have to redo the pH. Here's the sequence a working pro uses, and a calculator for every step.
1. Total alkalinity first
Alkalinity is pH's buffer — get it in range (80–120 ppm) first and pH becomes far easier to hold. Low alkalinity makes pH bounce; high alkalinity makes it drift up and cloud the water.
2. pH
With alkalinity set, bring pH to 7.4–7.6. This is also the fastest lever for your overall water balance (LSI). Use muriatic acid to lower it, soda ash (or aeration) to raise it.
3. Calcium hardness
Too little calcium and soft water attacks plaster and metal; too much and it scales. Plaster pools want 200–400 ppm; vinyl and fiberglass need less. You can only raise it chemically — lowering means dilution.
4. Cyanuric acid (CYA)
Stabilizer protects chlorine from sunlight, but it also sets how much chlorine you need. Get CYA where you want it (30–50 for chlorine pools, 60–80 for saltwater) before you set your chlorine target.
CYA calculator → · Lower high CYA →
5. Chlorine — last
Now set free chlorine to the right level for your CYA (about 7.5% of it). This is the step most people get wrong by using a flat "1–3 ppm," which is why stabilized pools still go green.
Then check your water balance
Once the five are set, confirm your Langelier Saturation Index (LSI) is between −0.3 and +0.3 — that's the single number that tells you the water won't etch or scale.
LSI calculator → · Or do all of this at once in the full Water Report →
Golden rules
- Change one thing, let it circulate, then re-test before the next.
- Add a little less than the maximum — it's easy to add more, hard to take it out.
- Always add chemical to water, never water to chemical, and never mix chemicals.