Wood-fired hot tub: complete manual for use and maintenance

Short answer: a wood-fired Q-tub requires four fixed habits: always fill before firing, put the cover on as soon as the tub isn't in use, one fixed weekly maintenance moment for water and filter, and a full water change with shell cleaning every 2 to 3 months. Keeping to these four habits gives you years of enjoyment from the tub. Below are the specifications per model, placement requirements, use, and the full maintenance calendar, with links to detailed instructions on each topic.

Specifications per model

All models have a fully insulated fibreglass shell with a wooden surround (thermowood or spruce) and are heated by an internal or external RVS316 stainless steel wood-fired heater (38 kW). Every model is also available as hybrid (wood plus electric element), electric, with a heat pump, or with a diesel heater; heating times for these are given in hot tub heating time. The position of the heater, control panel, drain and filter connection is determined per tub according to preference, so keep the assembly manual for your own version at hand.

Placement

• Base: flat, load-bearing and water-draining. A filled Q-tub XXL with eight bathers weighs over 2000 kilos; tiles or paving slabs on a compacted bed of crushed aggregate and coarse sand, or a concrete slab, are suitable. A wooden deck or roof terrace only after the load-bearing capacity has been assessed.
• Level: the shell must be truly horizontal. A tilted shell produces an uneven waterline, loads the walls unevenly and can leave part of an internal heater above the waterline.
• Clearance around the tub: at least 60 cm for maintenance, the ladder and the heater; with an external heater, follow the clearance to combustible material from the heater manual.
• Flue: clear of branches, roof edges and canopies, with smoke directed away from windows and the neighbours' terrace.
• Water and power: a tap point for the garden hose nearby; mains power only needed for an electric element or heat pump.

The complete preparation plan for delivery day is in preparing delivery and placement.

Use

1. Fill well above the top heater connection (with an internal heater, at least 5 cm above the top edge of the heater). Water first, then fire, always.
2. Fire with dry, split wood, air vent open while heating and closed down to hold the temperature. The complete instructions, including ash, draining and frost, are in wood-fired heater use and maintenance.
3. Temperature: 37 to 38 °C is ideal for most people; stir the water and measure with a floating thermometer in the middle of the tub.
4. Cover: on while heating and immediately after each use; the water surface is the biggest source of heat loss.
5. Showering before bathing keeps the water clean for longest; it is the cheapest form of water treatment.

The very first time is slightly different: see first start-up of your hot tub.

Maintenance calendar

The wood of the surround

The wooden surround is purely aesthetic and structural; the shell itself is fibreglass and the inside of the wood never gets wet. Thermowood can be left untreated to weather grey, or oiled annually to retain its colour; spruce needs an annual coat of stain or oil. Clean with water and a soft brush, never with a pressure washer, and don't treat it in full sun.

Safety

• Never fire without water, never drain with a hot heater.
• Never light with flammable liquids.
• Use a spark arrestor on the flue in wind, dry conditions and near overhanging vegetation.
• Never leave children unsupervised in or near the tub, and never on the heater side of an internal heater.
• No alcohol before or during bathing; those with heart or circulatory conditions, or who are pregnant, should consult a doctor first.
• Limit sessions to 15 to 20 minutes at 38 °C and drink enough water.