Ideal pool and hot tub chemistry levels
Quick answer: For a home chlorine pool, aim for free chlorine 2–4 ppm, pH 7.4–7.6, total alkalinity 80–120 ppm, stabilizer 30–50 ppm and calcium hardness 200–400 ppm. Hot tubs need more chlorine (3–5 ppm) and, per the CDC, no stabilizer.
Checked against 9 published sources (see them). Updated October 2026.
Free chlorine (ppm)
The chlorine that's free to kill germs. Don't swim above the limit on your product's label.
- Chlorine pool
- 2–4 ideal. At least 1, or at least 2 if you use stabilizer (CDC).
- Saltwater pool
- Pentair and Hayward list 1–3, but the CDC minimum is 2 when the water has stabilizer. CDC minimums are the same as a chlorine pool.
- Hot tub
- 3–5 ideal. At least 3 (CDC).
Combined chlorine (ppm)
Chlorine that's already used up. It causes the pool smell and red eyes. Total chlorine minus free chlorine.
- Chlorine pool
- 0.4 or less. CDC's public-pool code calls for action above that.
- Saltwater pool
- 0.4 or less.
- Hot tub
- 0.5 or less.
pH
How acidic the water is. Off-range pH makes chlorine work poorly and can irritate eyes and skin.
- Chlorine pool
- 7.4–7.6 ideal. Keep between 7.0 and 7.8 (CDC).
- Saltwater pool
- 7.4–7.6 ideal. Pentair says 7.2–7.8.
- Hot tub
- 7.4–7.6 ideal. Keep between 7.0 and 7.8 (CDC).
Total alkalinity (ppm)
A buffer that keeps pH from swinging. Low alkalinity lets pH bounce around.
- Chlorine pool
- 80–100 with liquid chlorine or cal-hypo; 100–120 with dichlor or trichlor. CDC's public-pool code allows 60–180.
- Saltwater pool
- 80–100 (Pool & Hot Tub Alliance). Pentair says 100–120; follow your cell's manual.
- Hot tub
- Same as a pool: 80–100 or 100–120 depending on your chlorine.
Stabilizer (CYA) (ppm)
Shields chlorine from sunlight. Too much makes chlorine slower to work, and it only comes down by draining.
- Chlorine pool
- 30–50 ideal. CDC's public-pool code caps it at 90.
- Saltwater pool
- 30–50 ideal. Check your cell's manual.
- Hot tub
- The CDC recommends not using stabilizer in hot tubs.
Calcium hardness (ppm)
Too little can etch plaster and grout; too much leaves scale and cloudy water.
- Chlorine pool
- 200–400 ideal. At least 150.
- Saltwater pool
- 200–400 ideal. Pentair says 200–300.
- Hot tub
- 150–250 ideal. At least 100.
Salt (ppm)
Salt cells turn salt into chlorine. Each model has its own target.
- Chlorine pool
- Not used.
- Saltwater pool
- Your cell's manual: Hayward AquaRite 3,200; Pentair IntelliChlor 3,400.
- Hot tub
- Only for spa salt systems; follow the manual.
How to use these numbers
Free chlorine and pH change fastest, so test those most often. The CDC advises testing both at least twice a day, and more when the pool is busy. Alkalinity moves slower; Hayward and South Australia's health department suggest testing it weekly. For calcium, Hayward says monthly and South Australia says weekly. Fix alkalinity before pH, because alkalinity decides how easily pH moves (Pool & Hot Tub Alliance).
The “ideal” bands are recommendations for comfortable, well-protected water. The CDC limits are the outer edges for safe swimming. Public and commercial pools follow their state or local health code, and some states set tighter limits.
Want to track it? Print the weekly test log; it has these targets printed at the top.
Sources
- CDC: Home pool and hot tub water treatment and testing
- CDC Model Aquatic Health Code, 2024 edition
- Pool & Hot Tub Alliance: Pool & Spa Management (2021), Appendix B
- Pool & Hot Tub Alliance fact sheet: Alkalinity
- Wojtowicz, "Swimming Pool and Spa Water Chemical Adjustments," Journal of the Swimming Pool and Spa Industry (2004)
- Pentair IntelliChlor IC15 installation and user's guide (salt table)
- Hayward AquaRite owner's manual
- Hayward: How often should you test your pool water
- SA Health (South Australia): Domestic swimming pools, water care
General guidance for home pools and hot tubs. Product labels and your equipment manual come first.