Hot tub water care
Target levels, a simple routine, and how often to drain and refill your spa.
When to drain and refill
Rule of thumb used by spa professionals: days between water changes = (gallons ÷ 3) ÷ average daily bathers. Drain sooner if the water foams, smells or won’t hold chlorine.
Typical hot tub levels
| Free chlorine | 3–5 ppm (bromine: 3–5 ppm) |
|---|---|
| pH | 7.4–7.8 |
| Total alkalinity | 50–80 ppm |
| Calcium hardness | 100–250 ppm (check your manufacturer) |
| Stabilizer (CYA) | 0–30 ppm |
| Temperature | No higher than 104°F (40°C) |
A simple routine
- Before or after each soak: test FC and pH; add chlorine to get back to 3–5 ppm. Hot water and bathers use up chlorine fast.
- Weekly: test alkalinity; rinse the filter cartridge every 1–2 weeks.
- Monthly: soak the filter in a cartridge cleaner; check calcium.
- Every few months: drain, clean the shell and refill (see calculator).
Use the chlorine, pH and alkalinity calculators with your spa volume, and set your My pool profile to “Hot tub” so targets switch automatically.
Health and safety
Keep water at or below 104°F. People who are pregnant, have heart conditions or take medication should check with a doctor before using a hot tub; young children overheat quickly. Always keep the cover locked when the spa is not in use.
Not professional advice. Results are estimates for residential pools and hot tubs. Read and follow product labels: add chemicals separately, to water (never water to chemicals), with the pump running, and retest before adding more. Commercial and public pools must follow local health codes.