Chlorine for Spas
Chlorine sanitizes hot tub water by killing bacteria and oxidizing organic waste. Learn why it is needed and how to manage it safely.
Need a dosing estimate? Open the free Spa Chemical Calculator.
Why this chemical is used
Chlorine is the primary sanitizer in many spas. It protects bathers by maintaining a measurable residual in the water.
When it is needed
Free chlorine is the portion available to sanitize. Combined chlorine is used-up chlorine attached to contaminants. If water smells harsh, the issue may be combined chlorine or poor oxidation, not too much free chlorine.
How to use it safely
- Test before adding anything.
- Calculate dose based on actual spa volume.
- Add chemicals separately with circulation running.
- Wait, circulate, and retest before adding more.
- Follow the product label and spa manufacturer instructions.
Small spas are easy to overdose. When unsure, add less, circulate, and retest.
Next step: test your water, enter your readings into the calculator, then adjust slowly and retest.