How-to
Testing a hot tub's water before anyone gets in
Test a hot tub's disinfectant, pH and temperature with test strips, read the results against the safe ranges, and set the house rules for using it.
Satisfy+ Editorial · Updated July 11, 2026 · 2 min read
At a glance
- Free chlorine
- At least 3 ppm, no more than 10
- Bromine
- 4 to 8 ppm
- pH
- 7.0 to 7.8
- Temperature
- No higher than 104°F
Germs such as Legionella, which causes Legionnaires' disease, and the bacteria behind hot tub rash grow in a hot tub that isn't kept at the right disinfectant and pH levels. A test strip tells you whether the water is ready. A public hot tub has its levels checked at least twice a day and at its busiest times, so test a home tub before each use and again when several people are using it.
What you need
- Test strips for chlorine or bromine and pH, from a hardware or pool supply store
- A thermometer, if the hot tub doesn't show the water temperature
Steps
- 1
Check the strips' expiration date
An expired strip can give a wrong reading.
1 min
- 2
Dip a strip and read it against the chart
Follow the timing on the bottle, then match each pad to the color chart.
2 min
- 3
Check the disinfectant
Free chlorine should be at least 3 parts per million and no more than 10. Bromine should be 4 to 8 parts per million.
1 min
- 4
Check the pH
It should read 7.0 to 7.8. Adjust the water if it's outside that range, and test again before anyone gets in.
1 min
- 5
Check the temperature
The water should be no hotter than 104°F (40°C).
1 min
- 6
Look and smell
The tiles or the shell shouldn't feel sticky or slippery. Properly treated water has little smell, and a strong chemical smell points to a problem.
1 min
- 7
Keep up the filter and the water
Scrub off any slime, replace the filter as the maker recommends, and change the water as often as the maker calls for.
10 min
Keep the hot tub water safe
- Get test strips for chlorine or bromine and pH
- Test the hot tub water before it's used
- Replace the hot tub filter on the maker's schedule
The house rules
Keep children under 5 out of the hot tub. Nobody drinks alcohol before or while using it, everyone showers first, and nobody swallows the water. Anyone sick with diarrhea stays out, and anyone pregnant should ask a doctor first. People 50 and older, current and former smokers, and people with chronic lung disease or a weakened immune system run a higher risk of Legionnaires' disease. Anyone who develops symptoms of Legionnaires' disease or Pontiac fever within two weeks of using a hot tub should see a doctor right away and mention the hot tub.
The pool and spa safety checklist covers the fence, the drains and supervision around the water.
FAQ
What should the chlorine level be in a hot tub?
Free chlorine should be at least 3 parts per million, and no more than 10.
What pH should hot tub water be?
Between 7.0 and 7.8.
How hot should a hot tub be?
No hotter than 104°F (40°C).
Sources
Checked October 19, 2026
- Centers for Disease Control and Prevention. What you can do to stay healthy in hot tubs (2025)
- Centers for Disease Control and Prevention. About protecting yourself from Legionella in hot tubs (2025)
- Owner
- Under $100
- Beginner
- Pool
- DIY
