Best Firewood for a Wood-Fired Hot Tub

What's the best wood for a hot tub?

• Very dry wood. Skargards says dry birch gives the best results, and that the drier the wood, the better.
• Birch or other hardwood. Kirami says that with birch or better wood, very few sparks leave the chimney, while pine, spruce and waste wood give more. UK retailer Layzee Living recommends kiln-dried hardwood such as oak, ash, beech and birch.
• Softwood to get it going. Layzee Living says softwood is useful for starting the fire but often burns faster.

Our mixed hardwood includes birch alongside oak, ash, beech and sycamore, all kiln dried below 20% moisture. Softwood costs less and catches quickly, so it's handy for getting the stove going.

What size should the logs be?

Skargards suggests logs about 5 by 5 by 40 cm, split into several smaller pieces, as small logs speed up heating. Kirami says to start with small, dry wood and add larger logs every 10 to 15 minutes as needed.

How much wood does a hot tub use?

• Kirami says one heat takes 60 to 120 litres of dry birch.
• Skargards says its Regal tub needs about 15 kg to reach bathing temperature, and its Panel tub about 30 kg.
• Skargards says to add logs every 20 minutes or so while heating, then a few every 30 minutes to hold the temperature.

Our tonne bag holds about 512 litres of logs, so on Kirami's figures that's roughly four to eight heats. If you use the tub every week, the XL tonne bag means fewer deliveries.

How long does a wood-fired hot tub take to heat?

• Kirami: about 2 to 3 hours for a 1,450-litre tub when it's 0°C outside.
• Skargards: about 2 hours from 6°C to 39°C in summer, and up to 3.5 hours in the coldest months.
• Hikki: about 1.5 hours in summer and 2.5 hours in winter for its Bohemen tub.

Skargards says an insulated lid can make heating up to 30% faster in winter, and Kirami says to keep the tub covered while it heats.

Internal or external stove?

It's a trade-off. Kirami says almost all external heaters are more efficient than internal ones and leave more room in the tub. Gadero says internally heated tubs heat up much quicker.

How do I use a hot tub stove safely?

• Make sure there's water in the tub before you light the stove, as Kirami says.
• Never leave the fire unsupervised, and keep a non-flammable guard in front of the fire chamber.
• Never light it with fluids that aren't meant for the job.
• Don't burn paper: Skargards says the ash can leave the flue and fall into the tub.
• Keep a bucket of cold water or a hose nearby to cool the water quickly, Skargards says. It recommends a bathing temperature of 39°C, and Canopy & Stars says overheating above 40°C is a common mistake.
• Never burn treated or painted wood.

Do smoke control rules apply to a hot tub?

Defra's guidance for councils says smoke from outdoor burning isn't covered by smoke control rules, including barbecues, chimineas and pizza ovens that are outside and not in a building. It defines a building as any structure with a roof and walls, including sheds and summerhouses. Hot tubs aren't named, so if yours is inside an enclosed hut, check with your council. Either way, your council can still act if the smoke becomes a nuisance.