Alternatives to Chlorine for Your Hot Tub: What Actually Works

Last updated: September 2026

Chlorine is the most popular and common way to keep a hot tub clean, but it isn’t right for everyone or every setup. Some people can’t stand the smell, and others find it irritates their skin and eyes. In this article I’ll look at the alternatives, what each one really does, and which might suit you.

By the end you’ll have a much better idea of which sanitiser is right for you. So let’s get to it.

Exploring alternatives to chlorine for your hot tub

For years, chlorine has been the go-to hot tub sanitiser, and it keeps water clean and bacteria-free. But not everyone is a fan. Some people find the smell unpleasant, and others get skin irritation. If chlorine isn’t working for you, there are several alternatives. The most important thing to remember is that a hot tub is a warm, busy bowl of water, so whatever you use has to keep killing bugs the whole time. Test it as carefully as you’d test chlorine.

Bromine: a gentle and effective alternative

Bromine is the most popular alternative. It works in a similar way, killing bacteria and keeping the water clean, with a few advantages. It has a much milder smell, and it’s gentler on skin for many people.

The best part is that if you’re switching from chlorine to bromine, you don’t need to change your hot tub setup. Your filters, plumbing and other equipment work as they are. Bromine usually costs more than chlorine, though, and you’ll want a floating or cartridge feeder. Bromine tablets also contain chlorine compounds, so it isn’t the answer if you have a true chlorine sensitivity. For the full comparison, read bromine or chlorine in a hot tub.

Ozone: a supplemental sanitiser

Ozone doesn’t fully replace chlorine or bromine. It works alongside them to boost their effect, killing bacteria and contaminants and reducing the chemical you need. But an ozone generator has to be fitted into your plumbing, and results vary. Some users, including experienced DIY builders, report difficulty getting it to work properly, so expect some trial and error. See ozone in a hot tub.

UV systems: reducing chemical use

Like ozone, UV (ultraviolet) doesn’t remove the need for chlorine or bromine. A UV unit uses light to kill bacteria and microorganisms as the water passes through it, so you need less sanitiser and the water stays clear. On its own it doesn’t leave any sanitiser in the water, so you’ll still need a chemical to keep the water balanced and safe. If you want to cut down on chlorine or bromine rather than eliminate it, UV can be a worthwhile investment.

Active oxygen: a chlorine-free option

If you want to move away from chlorine altogether, active oxygen is the option most owners choose. It’s also known as non-chlorine shock. The key ingredient is potassium peroxymonosulfate (MPS), a powerful oxidiser that breaks down contaminants without chlorine. It’s an oxidiser, not a full replacement for a disinfectant, so most chlorine-free regimes pair it with a separate sanitiser product. Follow the product’s instructions and test the water.

It’s odourless, gentle on skin and kinder to the environment. It’s also much gentler on plants than chlorine or bromine, though I’d still check the label and any local rules before you drain onto the lawn. For a fuller look at how it works, see hot tub shock.

Copper and silver ionisers, and salt

Ionisers release copper and silver ions into the water. They work well alongside a low level of sanitiser and can cut chemical use, but they aren’t a complete answer on their own. Read copper/silver ionisation. Salt systems turn dissolved salt into chlorine, so the water is chlorinated, just without you handling the chemical. See saltwater in a hot tub.

What’s the right sanitiser for my hot tub?

When choosing, think about skin sensitivity, maintenance and cost.

Option	Best for	Watch out for
Bromine	A direct swap with no new equipment	Costs more, and tablets still contain chlorine compounds
Ozone or UV plus a low level of sanitiser	Cutting chemical use	Cost, and results vary, and you still need sanitiser
Active oxygen	A chlorine-free routine	Needs disciplined testing, and a separate sanitiser product
Copper/silver	Extra help alongside sanitiser	Can stain, and isn’t a stand-alone solution
Salt system	Avoiding handling chlorine	It’s still chlorine, and can corrode some fittings

Whichever you choose, keep pH at 7.2 to 7.6 and total alkalinity at 80 to 120 ppm, and keep cyanuric acid as low as possible. Read my chemical balancing guide for the rest. If you’re on chlorine or bromine, aim for free chlorine 3 to 5 ppm or bromine 4 to 6 ppm.

If you’re ready to make the switch, take a look at the products available on my store at parts4tubs.com, or browse parts4tubs.co.uk in the UK. For everyday care, see my beginner’s guide to hot tub maintenance.

FAQs

What is the best alternative to chlorine for a hot tub?

Bromine is the easiest swap, and active oxygen is the most popular chlorine-free option. The best one depends on your skin, budget and how much testing you’re happy to do.

Can I run a hot tub without chlorine?

Yes, but you still need a sanitiser that leaves a residual in the water. Options include bromine (which isn’t chlorine-free), active oxygen regimes or ionisers used with care. Test regularly.

Is bromine chlorine-free?

No. Bromine tablets contain chlorine compounds. If you have a chlorine sensitivity, ask a doctor and look at chlorine-free regimes.

Do ozone and UV replace chlorine?

No. They reduce the amount of chlorine or bromine you need, but you still need a sanitiser in the water.

Can I drain hot tub water onto my lawn?

Active oxygen water is gentler on plants than chlorinated water, but check the product label and local rules, and let any sanitiser level fall first.

Got a question about your own tub? Drop it in the comments below. I read them all.

Cheers,
Andi

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Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi