How much chlorine should a hot tub have?
Short answer
CDC says keep free chlorine at 3 ppm or more in a hot tub, and bromine at 4 to 8 ppm. Maker manuals mostly aim for 2 to 5 ppm chlorine, and Hot Spring says to let it fall below 5 before you get in.
What CDC and each maker's manual say
7 sources
| Free chlorine | Bromine | |
|---|---|---|
| CDCAdvice for hot tub users | 3 ppm or more | 4 to 8 ppm |
| CDC Legionella toolkitWritten for public and display hot tubs | 3 to 10 ppm | 4 to 8 ppm |
| BullfrogX Series manual, 2026 | 3.0 to 5.0 ppm | 3.0 to 6.0 ppm |
| Hot SpringHighlife manual, 2026 | 3 to 5 ppm (1 to 5 acceptable) | Granular only; no range given |
| JacuzziJ-300 manual, 2025; chlorine figure is for its cartridge system | 0.5 to 1.0 ppm | Not given |
| Master SpasTwilight manual, 2026 | 2 to 4 ppm | 3 to 5 ppm |
| Sundance880 manual, 2025; without its UV system running | 3.0 to 4.0 ppm | 2.0 to 4.0 ppm |
What is the difference between free and total chlorine?
Free chlorine is the part still able to kill germs. Once chlorine reacts with sweat, oils and urine it becomes combined chlorine (chloramines), which is weak and smells strongly. Total chlorine is the two added together. When free reads lower than total, Master Spas says to add a non-chlorine shock to burn off the combined part. See how to shock a hot tub.
Why does hot tub chlorine run out so fast?
A hot tub holds a few hundred gallons of hot water and puts several bodies in it at once, so the load per gallon is far higher than in a pool. Heat speeds it up: Hot Spring's manual says chlorine lasts substantially longer at 80°F than at 101 to 104°F. It suggests testing daily for the first month to learn your own use, since two people for twenty minutes a day sets a very different demand from a weekend with guests.
What if hot tub chlorine is too high?
Which kind of chlorine goes in a hot tub?
Sodium dichlor granules are the makers' first choice: Master Spas approves only dichlor, and Hot Spring lists dichlor and liquid sodium hypochlorite. Hot Spring warns against trichlor: its pH of 2.6 and fast dissolving in hot water push chlorine high enough to damage the spa.
One point where the sources disagree: CDC recommends no cyanuric acid or stabilized chlorine in hot tubs because it slows disinfection, while dichlor is a stabilized chlorine that the makers still list first. If you use it, watch cyanuric acid; Bullfrog's balance guideline is 0 to 50 ppm. For bromine, see chlorine vs bromine.
How much to add
The product label sets the dose, by your tub's gallons.
Strengths differ between brands of the same chemical, so we don't print amounts. Test, read the label, add a little at a time with the jets running, wait, and test again. Your tub's gallons are in its manual or in our gallons and filter size table.
The details
The full tables, the figures behind each sentence and where they come from.
Common questions
How much chlorine should be in a hot tub?
CDC says at least 3 ppm of free chlorine. Maker manuals mostly aim for 2 to 5 ppm, and Hot Spring says to let it fall below 5 ppm before use.
What bromine level should a hot tub have?
CDC says 4 to 8 ppm. Maker figures run from 2 to 4 ppm at Sundance to 3 to 6 ppm at Bullfrog.
Can you get in a hot tub with high chlorine?
Hot Spring says wait until free chlorine falls below 5 ppm. Leave the cover off and it drops on its own.
Sources
7
- CDC: What you can do to stay healthy in hot tubsChlorine at least 3 ppm, bromine 4 to 8 ppm, pH 7.0 to 7.8, water no hotter than 104°F
- CDC: Home pool and hot tub water treatment and testingpH 7.0 to 7.8, no cyanuric acid in hot tubs, DPD kits more accurate than strips
- Hot Spring Highlife Collection owner's manual, 2026
- Master Spas Twilight Series owner's manual, 2026
- Bullfrog X Series owner's manual, 2026
- Sundance 880 Series owner's manual, 2025 (Rev E)
- Jacuzzi J-300 Collection owner's manual, 2025 (Rev E)
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