Legionella prevention in hot tubs
Updated October 2026
Hot tub water sits right in the temperature range where legionella bacteria grow. That’s why the sanitiser, filters and pipework matter. Here’s how to keep the risk low in a home tub.
Why hot tubs need care
Legionella bacteria live in water at low levels. At hot tub temperatures they can multiply, especially in biofilm: the slimy layer that builds up inside pipes, jets and filters.
People catch Legionnaires’ disease by breathing in tiny droplets from bubbling water, not by swallowing it. Older people, smokers and anyone with a weakened immune system are most at risk.
The 40°C maximum on most tubs is there for bather safety. It doesn’t control legionella.
How to keep the risk low
- Keep the chlorine or bromine in range and the pH at 7.2 to 7.6. Test before every use.
- Shock once a week, and after a busy session.
- Rinse the filters weekly and deep-clean them every two to four weeks.
- Use a pipe cleaner (a biofilm remover) before every drain, then clean the shell and refill.
- Change the water regularly. Your manual gives a guide to how often.
- Keep the tub running and dosed. Don’t leave water standing in a tub that’s switched off.
Levels for each sanitiser are in the chlorine guide and the bromine guide.
Different rules apply
If guests or the public use the tub, you’re responsible for controlling legionella under health and safety law. That means a risk assessment, a written scheme, set testing and records. See our HSG282 guidance for what’s involved.
We can take on the regular cleans and checks. Keeping the risk assessment and records up to date stays with the owner or operator.
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If your tub is sunk into decking or the ground, or set against a wall, it helps to mention it when you book. If you’re not sure, a photo is fine.
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