Keep the Water Clear With the Right Sanitiser
Keep the water clear with the right sanitiser
Bromine and non-chlorine shock keep hot tub water clean. They work in different ways, so this guide sets out how to choose a main sanitiser, the levels to hold, and the products we stock to do the job.
Two numbers do most of the work: a pH between 7.0 and 7.8, and at least 3 ppm of free sanitiser.
Choose your sanitiser
Choose one main sanitiser and follow the product label for dosing. For a hot tub, use a sanitiser without cyanuric acid. Stabilised chlorine contains cyanuric acid, and the CDC advises against it in hot tubs.1
| Option | What it is | Best for |
|---|---|---|
| Bromine | Granules. A gentle, stable main sanitiser for hot tubs. | Everyday sanitising, and sensitive skin |
| Non-chlorine shock | Granules. A shock treatment, used alongside your main sanitiser. | Weekly boost, not a main sanitiser |
Hold the levels
The water should stay in these ranges, and you should test it at least twice a day. Test more often on busy days.1
A weekly routine that holds
Most of the work is a few minutes a day. Test the water, adjust pH if it has drifted, and top up the sanitiser to the range above. Once a week, give the tub a shock with non-chlorine granules.
Test
Check the free sanitiser and pH with the test tablets.
Adjust pH
Use pH minus if the reading is high and pH plus if it is low.
Sanitise
Dose the main sanitiser to bring it back into the range above.
Shock weekly
A non-chlorine shock lifts the water once a week, especially after a busy weekend.
What to use
Both are in stock now. For the pH, pick up the pH minus or pH plus, and the DPD test tablets for daily checks.
1 kg or 5 kg · from £17.99
A gentle main sanitiser for hot tubs. Follow the label for dosing.
Hot Tub Non Chlorine Shock Granules
1 kg · £16.99
The weekly boost. Use it once a week, or after a busy session, to lift the water between sanitiser doses.
Quick answers
Open a question to read the answer.
Is bromine or chlorine better for a hot tub?
Both can sanitise a hot tub. Choose one main sanitiser, follow the label, and avoid stabilised chlorine, which contains cyanuric acid.
How much free chlorine should a hot tub have?
At least 3 ppm, according to the CDC. Test at least twice a day, and more often when the tub is busy.
What pH should a hot tub be?
Between 7.0 and 7.8. Outside that range, the sanitiser works less well and the water can feel uncomfortable.
Do I need to shock my hot tub?
A weekly shock keeps the water fresh. Use a non-chlorine shock once a week, and after a busy session.
Can I mix chlorine and bromine?
Choose one main sanitiser and follow the label. If you change to another, test the water before the next bathe.
How often should I test the water?
At least twice a day. Keep a test kit by the tub so checking takes a minute.
Paul Margerison
Managing Director & Founder, Outdoor Living
Clear water is a routine, not a one-off job. This guide sets out the few numbers that matter and the products to keep them there.