Hot tub chlorine level
Aim for 3 to 5 ppm (parts per million) of free chlorine as the right hot tub chlorine level. Soaking above 5 ppm is banned by the EPA-registered dichlor label, with CDC setting 3 ppm as the minimum. For bromine, keep levels between 4 and 6 ppm.
Find how much to add by picking your tub and chlorine reading.
- The free form of chlorine
- 3–5 ppm
- Limit for soaking on the EPA label
- 5 ppm
- Bromine
- 4–6 ppm
- Amount of Dichlor needed per 100 gal for 1 ppm
- 0.7 g
Ideal hot tub chlorine level
Hot tubs need at least 3 ppm, the CDC says, while pools call for 1 ppm. Chlorine gets used up by dirt, sweat, and spray from the jets. The EPA dichlor label sets the maximum: do not soak above 5 ppm.
| Free chlorine pad | What it means | What to do |
|---|---|---|
| 0 to 1 ppm | Too low: germs can grow | Add chlorine now; shock if cloudy or smelly |
| 2 ppm | Low | Add chlorine to reach 4 ppm |
| 3–5 ppm | Right | Nothing to add |
| Over 5 ppm | Too high to soak | Lid off, jets on, wait |
| 0 right after a shock | Pad may be bleached out | Test again later; levels over 10 ppm may show as 0. |
A CDC warning about strips appears in the final row. If chlorine exceeds 10 ppm, it can bleach the pad and cause a falsely low result.
Free, total, and combined chlorine compared
Free chlorine is the part that can still clean the water. Sweat and oils react with chlorine to form combined chlorine, which stops working. Total chlorine represents the sum of both types.
If total reads higher than free, your tub holds used-up chlorine. The strong pool smell comes from these compounds, called chloramines, Bullfrog says. To clear them, American Whirlpool uses a shock.
With bromine, things work differently. Since its combined form still kills germs, strips measure total bromine, and you should follow that number.
How much chlorine should you add?
These amounts of chlorine granules (sodium dichlor) raise free chlorine to 4 ppm, the midpoint of the range.
| Pad reads | 250 gal (950 L) | 350 gal (1,320 L) | 500 gal (1,890 L) |
|---|---|---|---|
| 0 ppm | 0.24 oz (6.8 g) | 0.33 oz (9.5 g) | 0.48 oz (13.5 g) |
| 1 ppm | 0.18 oz (5.1 g) | 0.25 oz (7.1 g) | 0.36 oz (10.1 g) |
| 2 ppm | 0.12 oz (3.4 g) | 0.17 oz (4.7 g) | 0.24 oz (6.8 g) |
These doses rely on the 56% available chlorine found on the EPA dichlor label. Sprinkle the granules across the water surface while the jets run. As the label directs, wait 5 minutes then test again. Use the chemical calculator if your tub uses bromine.
Hot tub chlorine too low: steps to take
If the reading sits under 3 ppm, germs may grow, so sort it out before you soak again. CDC lists sweat and dirt from soakers, sun and jet mist as things that use chlorine up.
- Put in chlorine granules. Consult the chlorine chart or use the calculator for your specific volume. Every dose targets 4 ppm.
- Shock the water if it looks cloudy or has an odor. A shock also helps if total chlorine reads higher than free chlorine.
- Test the pH level. Maintain it between 7.4 and 7.6, since CDC notes that chlorine becomes less effective at killing germs as pH increases. Follow the pH down guide if your reading is too high.
- Put the cover back on whenever you are not soaking. This blocks sunlight from reaching the water.
- Test the water more frequently after periods of heavy use. Chlorine drains fastest during heavy use.
Hot tub chlorine too high: what to do
- Do not get in the water. The EPA label prohibits soaking above 5 ppm, and Lay-Z-Spa strongly warns against using its tubs above 5 ppm.
- Remove the cover and turn on the jets. CDC identifies jet spray and sunlight as factors that reduce chlorine levels. Keeping the lid on traps the gas inside.
- Give it time, then test again. Do not add more chlorine until the test pad shows 5 ppm or lower.
- Drain some water if the level stays high. Lay-Z-Spa dilutes the water by draining some and refilling with fresh. Learn how to drain a hot tub.
A shock can leave hot tub chlorine too high for a while, and that is normal. Keep the lid off and wait to soak until the test pad returns to the proper range.
Hot tub bromine too high
Bromine is at its best between 4 and 6 ppm. Public tubs should stay below the manufacturer's top limit, CDC says. Leslie's is stricter and keeps soakers out above 5 ppm, which makes 4 to 5 ppm the safer band. Low pH plus very high bromine can also make the water yellow red.
Fixing hot tub bromine too high follows the same steps as fixing chlorine. Lower or remove the floater, take off the lid, and run the jets. Test the water again before you soak, and drain some water if the level does not fall.
Maintaining proper chlorine levels
- Test before every soak like the Hot Spring manual recommends, and do not add anything if the level is correct.
- Maintain pH levels between 7.4 and 7.6. CDC states that rising pH makes chlorine less effective at killing germs.
- Apply a shock treatment roughly once a week and after heavy usage, as Leslie's suggests.
- Do not use stabilizer. CDC recommends avoiding cyanuric acid in hot tubs because it reduces chlorine effectiveness.
- Check every pad using test strips, not just the chlorine one.
Common questions
What is the right chlorine level for a hot tub?
Maintain free chlorine between 3 and 5 ppm. Soaking above 5 ppm is barred by the EPA-registered dichlor label, with CDC setting 3 ppm as the hot tub minimum.
Is it safe to enter a hot tub with high chlorine?
Do not enter if levels exceed 5 ppm. Keep the jets running and the cover off. Test the water again, then get in.
Is chlorine at 10 ppm too high in a hot tub?
It is. That is twice the 5 ppm soaking limit, so avoid entering and keep the lid off. Above 10 ppm, the CDC warns that strips may bleach and show a false 0 reading.
Why does my hot tub smell like chlorine?
Usually a strong smell means chloramines, which are used-up chlorine, not too much chlorine. Chlorine reacts with sweat and oils to form them, and a shock clears them.
In a hot tub, what level of bromine counts as safe?
The range to target is 4 to 6 ppm. CDC's floor for public tubs is 4 ppm. Leslie's recommends avoiding soaking above 5 ppm, making the lower end of the range safer.