How do I use bromine in my hot tub?

Why use bromine?

Bromine does the same job as chlorine - it kills bacteria and breaks down waste - but it copes better with the warm water in a hot tub and stays effective across a wider pH range. Many people also find it gentler on skin with less smell.

It is usually added as slow-dissolving tablets in a floating dispenser or inline feeder, so levels stay steadier than with granules.

Reading bromine on a 6-in-1 strip

Bromine shows up on the free chlorine pad. The pack has a separate bromine scale, which reads roughly 2.2 times the chlorine value. When you set your hot tub's sanitiser to bromine in the app, it converts the reading and shows the right ideal range for you.

Ignore the total chlorine pad in a bromine hot tub - it is not meaningful, so the app hides it.

Getting bromine started

Bromine tablets dissolve slowly, so a freshly filled hot tub takes a day or two to build up a reading. To speed this up, add a shock after filling - it activates the bromide in the water.

• Balance the water first: alkalinity 80-120 ppm, then pH 7.2-7.8.
• Fill the floating dispenser with bromine tablets and set it to a medium opening. Never put tablets directly in the skimmer or loose in the tub, where they can damage the shell and heater.
• Shock the water with the jets running and the lid open for 20-30 minutes.
• Retest after 24 hours and adjust the dispenser opening up or down.

Keeping it in range

• Test before each use, or at least twice a week.
• If bromine is low, open the dispenser a notch and check it has tablets. Remember bromine rises slowly - retest after 24 hours.
• If bromine is high, close the dispenser down or take it out, and leave the lid open with the jets running.
• Shock weekly and after heavy use to reactivate spent bromide and break down oils.
• Never mix bromine and chlorine tablets in the same dispenser or feeder.

When to call a professional

If the water smells musty, foams or stays cloudy despite a good bromine reading, the water may simply be old - drain and refill. If problems continue after a refill, a hot tub technician can check for biofilm in the pipework or a faulty ozone or UV unit.

Frequently asked questions