Can I Use Chemicals in a Wood‑Fired Hot Tub?

Wood-fired hot tubs offer a natural, relaxing experience — warm water, crackling fire, and no noisy pumps. But one question always comes up: do you need chemicals in a wood-fired hot tub?

The short answer: yes, you can use chemicals — but only the right ones. And one chemical in particular must never be used.

Do Wood-Fired Hot Tubs Need Chemicals?

It depends on how you use your tub:

• If you empty the tub after every use (same day): You do not need chemicals. Just fill, heat, enjoy, and empty.
• If you keep the water for several days: You must use chemicals to keep the water safe.
• If your tub has a filtration system: You treat it more like a standard hot tub — but with different chemical rules.

The Most Important Rule: Never Use Bromine

Bromine cannot be used in a wood-fired hot tub. Bromine will corrode stainless steel, including heaters, flues, and fittings — even 316-grade stainless steel. Bromine + stainless steel = corrosion.

Safe Chemicals You Can Use

Low-Dose Chlorine

Use stabilised chlorine granules at 1–3 ppm. Pre-dissolve before adding. Safe for stainless steel when used correctly.

Non-Chlorine Shock (MPS)

Ideal for multi-day use, odour reduction, and clear water. Safe for all wood-fired tubs.

pH and Alkalinity Control

Keep pH between 7.2–7.6 and alkalinity between 80–120 ppm to protect metal parts and improve sanitiser performance.

Natural and Low-Chemical Options

• Empty after each use: The safest chemical-free method.
• Use non-chlorine shock for short-term use: Great for weekend water retention.
• UV or ozone systems: Reduce chemical demand but don’t replace sanitiser entirely.

How Often Should You Change the Water?

Final Advice

You can use chemicals in a wood-fired hot tub — but only the right ones. Avoid bromine completely to protect stainless steel components. Use low-dose chlorine, non-chlorine shock, and maintain proper pH and alkalinity for safe, clean water.

Frequently Asked Questions

Can I use chemicals in a wood-fired hot tub?

Yes, but only safe ones like low-dose chlorine or non-chlorine shock. Avoid bromine entirely.

Why can’t bromine be used?

Bromine reacts with stainless steel, causing corrosion and long-term damage to heaters and fittings.

What are safe alternatives to bromine?

Use stabilised chlorine granules, non-chlorine shock (MPS), and maintain balanced pH and alkalinity.

Do I need chemicals if I empty the tub after each use?

No. If you drain the water after every session, you don’t need any chemicals.

How often should I change the water?

Single use: after each session. Weekend use: every 2–3 days. With filtration: every 1–2 weeks.