Pool Chemistry Levels Chart (Chlorine, pH, Alkalinity, CYA, Calcium)
There is no single national code for home pools in the U.S. The two most useful references are the CDC's recommendations for home pools and the public pool codes that state and city health departments enforce. This chart puts them side by side.
The chart
| Reading | CDC, home pools | Public pool code (Columbus, Ohio): minimum or limit | Public pool code: ideal |
|---|---|---|---|
| Free chlorine, pool | at least 1 ppm | at least 1 ppm | 2–4 ppm |
| Free chlorine, pool with cyanuric acid | at least 2 ppm | — | — |
| Free chlorine, hot tub / spa | at least 3 ppm | at least 2 ppm | 3–5 ppm |
| Combined chlorine | — | less than 1 ppm | 0 ppm |
| pH | 7.0–7.8 | 7.2 to 7.8 | 7.4–7.6 |
| Total alkalinity | — | at least 60 ppm | 80–120 ppm |
| Calcium hardness, pool | — | — | 200–400 ppm |
| Calcium hardness, spa | — | — | 150–250 ppm |
| Cyanuric acid (stabilizer) | not advised in hot tubs | less than 70 ppm; above 100 ppm the pool is closed | 30–50 ppm |
A dash means that source does not give a figure. Public pool codes are written for pools open to the public and differ from state to state. They are shown here because they are specific, published and enforced, not because a home pool must meet them.
How to use it
- Test first. The CDC says DPD test kits are the most accurate; test strips are less accurate. Test chlorine and pH at least twice a day, and more often when the pool is busy.
- Raise levels with the right amount. The pool chemical calculator turns "current" and "target" readings into a dose for your gallons and your product's strength.
- Lower stabilizer, calcium or salt by replacing water. Chemicals can't remove them. The calculator also gives the share of water to drain and refill.
Notes on each reading
- Free chlorine is the chlorine still available to kill germs. The CDC figure is a minimum, and the CDC advises testing more often when the pool is heavily used.
- Cyanuric acid (stabilizer): the CDC says pools using it should keep chlorine at 2 ppm or more, and it advises against using it in hot tubs. Trichlor and dichlor products add cyanuric acid every time you use them.
- pH affects how well chlorine works and how the water feels. The CDC range is 7.0–7.8.
Sources
- U.S. Centers for Disease Control and Prevention, Home Pool and Hot Tub Water Treatment and Testing (updated May 10, 2024).
- Columbus Public Health, Water Chemistry Parameters.