Why We Recommend Chlorine for Your Hot Tub (and When to Use Bromine)

Every hot tub needs a sanitiser, the chemical that kills bacteria and keeps the water safe to sit in. For Canadian Spa Company hot tubs, we recommend chlorine. It sanitises and clarifies the water at the same time, so one product does most of the work and day-to-day upkeep stays easy and simple. Bromine is there as an alternative if someone in your household is allergic or sensitive to chlorine.

What a sanitiser does

Every soak adds sweat, skin oils, lotions and bacteria to the water. The sanitiser stays in the water and keeps working between filter cycles, killing germs and breaking down that organic waste. Filters, ozone and UV all help, but none of them leaves a lasting level of sanitiser in the water, so you still need a sanitiser on top. It only works properly when the pH and alkalinity are in range.

Why we recommend chlorine

Chlorine is mainly what we sell and what we use, because it keeps things simple. As well as killing bacteria, it clears the water, so a correctly dosed spa stays clean and clear without a cupboard full of extra products. Our chlorine granules dissolve quickly, they're easy to dose and control, and they work well across the range of UK water types.

Keeping it in range

• Aim for 1.0 to 1.5 ppm free chlorine, with the pH at 7.2 to 7.6.
• Our 3-in-1 Test Strips (£5.99 for 50) read free chlorine, pH and total alkalinity in one dip, so a single test tells you everything you need.
• Test two to three times a week, and again after a busy weekend.

Dosing

Chlorine Granules (500g, £9.99) can go straight in when the water is above 20°C. Below 20°C, dissolve them in a plastic container of water first. Leave the pump running so they mix in.

If you'd rather not dose by hand, Chlorine Tablets (800g, £22) are made for a floating dispenser and aren't suitable for manual daily dosing. A Spa Floating Dispenser (£15) sits on the water and releases sanitiser at a steady rate. That avoids the spike you get straight after a manual dose and keeps some sanitiser in the water between adjustments.

Steady pH

Once you've made the first adjustment after filling with tap water, the pH usually stays steady with our chlorine. If it starts drifting up and down, too much detergent has built up in the water and it's time for a change. Most owners change their water every four to six months, depending on use. Our guide to draining and refilling a hot tub walks you through it.

Itchy skin or sore eyes? Check the water first

If anyone gets itchy skin or sore eyes after a soak, don't assume it's the chlorine. Most irritation comes from water that's out of balance, such as the wrong pH or a build-up of spent chlorine, rather than from chlorine at the right level. Read our guide to itchy skin and sore eyes after a hot tub and test before you change anything.

Bromine: the alternative for chlorine allergies

If someone in your household is allergic or sensitive to chlorine, bromine is an alternative sanitiser that works with our hot tubs. If you think someone may have an allergy, speak to your GP or a pharmacist before you choose. Bromine does need a little more attention, because it tends to lower total alkalinity over time, which pulls the pH down.

• Keep the bromine reading at 4 to 6 ppm, with the pH at 7.4 to 7.6.
• Test with a bromine test kit. Our 3-in-1 strips read chlorine, so they won't give you a bromine level.
• Bromine Tablets (700g, £30) go in a floating dispenser or an erosion feeder only, never loose in the water. One tablet typically treats 1,000 litres. Above that, use at least two tablets, then adjust the dispenser or feeder if the reading runs high or low.
• Check alkalinity at every test so the pH doesn't slide.

Never mix bromine with chlorine products, in the water or in storage, as a dangerous reaction can happen. If you're changing over, stop adding your current sanitiser, drain, clean and refill the spa, rinse or replace the filters, balance alkalinity and pH, then add the new sanitiser. Use a separate, clearly labelled dispenser for each.

Common questions

Do I still need to shock the water?

Yes. A non-chlorine spa shock breaks down the oils and waste the filter can't catch, and it works alongside chlorine or bromine.

Does a Glacier filter or UV system mean I can skip the sanitiser?

No. They reduce how much sanitiser you need, but a measured level of sanitiser is still needed to keep the water safe.

Is chlorine fine for children?

Yes, at the right level. What matters is testing regularly and keeping the readings in range. If anyone in the family has a skin condition, check with your GP before using a hot tub. You shouldn't use a hot tub while pregnant.

For the full order of testing and dosing, see our step-by-step hot tub chemistry guide. If you have a question about your water or which sanitiser suits your household, call Canadian Spa Company on 01293 824094 and we'll talk it through with you.