A teak hot tub for the evening: 38 °C, a white liner, and not a hoop on it

The hills product: a hot tub is best where the night gets cold

Around Chiang Mai the January night falls to about 16 °C on average (Thai Meteorological Department, 1991-2020 normals, Chiang Mai), and the weekend houses around Khao Yai have their own cooler evenings through the dry season. That is hot tub weather: 38 °C on a dark deck with a ridge behind it, twenty minutes after dinner, covered again before bed. On the coast the same tub is a cool-season and evening object, and in April it is mostly a handsome planter until the display is turned down to 36 °C. A buyer in Phuket should know that; a buyer in Mae Rim already does.

Teak or thermo-ash outside, always white inside

Hot water is harder on timber than cold: wood kept wet at 38 °C swells, breeds film and leaks at the joints within a season or two. So the staves on our tubs are cladding, and the water sits in a smooth white fibreglass liner. The white rim above the waterline is deliberate: it shows the level, it shows when it is time to wipe, and it keeps the tub from looking like a barrel. There are no metal hoops, because hoops rust in humid air and burn a bare arm once the sun has been on them. Teak is the default outdoors in the tropics; thermally modified ash gives a darker, more even colour and moves less in the wet season; cedar suits a covered terrace. The timber field note compares the three.

A wooden tub against an acrylic spa shell

The wooden tub wins on looks, on simplicity and on being able to leave with you; the hydromassage hot tub wins on jets, seating depth and the right to be used by paying guests. An amenity in a rental is the built-in product, for the same reason our teak cold tubs are private only: traffic, hygiene duty and a routine a housekeeper can be asked to follow.

Heating 1,400 litres with a wire rather than a fire

Taking 1,400 litres from a 29 °C fill to 38 °C needs about 14.7 kWh, which is 4.9 hours on a 3 kW heater or 2.4 on a 6 kW one; after that the heater only replaces what the cover lets out, a little on a 25 °C evening and almost nothing on a 30 °C one. A timer has the tub ready at dusk and never heats water in the heat of the day. People ask about wood-fired stoves, especially in the north; whether one is acceptable on your plot depends on smoke, neighbours and the local office, so ask us and we will say what is possible rather than list it as standard.

Where it stands: the deck, the drain and a dry cupboard

• Weight first. A 1,400 litre tub with four people in it weighs close to two tonnes on about two square metres; a new deck is framed for it, an existing deck or slab is checked, not assumed.
• A drain within a hose length. Warm, sanitised water goes to a drain or a soakaway, not across the lawn in one evening; the fill comes from a tap.
• A dry heater cupboard. Heater, pump and filter sit in a ventilated box within three metres, off the ground and out of the rain, on a short lagged pipe run.
• Electricity. A 3 kW heater runs single-phase at 220⁠-⁠230 V on an ordinary 30(100) A meter; a 6 kW heater next to a sauna or a chiller is where we wire three-phase, as our practice. Ask PEA what the house meter can take before the tub is ordered.
• Termites and splash. The tub stands on a stone pad or a raised, ventilated teak base, never on timber in contact with soil, and the cover goes on before the rain does.

Hot teak beside cold teak: a private pair

The natural partner is the teak cold tub in the same timber on the same deck: 38 °C in one, 3⁠-⁠5 °C in the other, three steps between them, the chiller and the heater in a shared cupboard. For a cheaper cold side while you decide, the inflatable ice bath does the job for a season. The budget ranges page lists the hot tub next to the cold sets so the pair can be summed; the configurator prices the cold side and the sauna, not yet the hot tub.

Care in a wet climate: oil, wipe, cover

Oil the teak once a year to keep the honey colour or let it go silver; thermally modified ash is usually left alone. Wipe the liner at the waterline when you change the water, run the filter daily on its timer, keep the sanitiser in range, and keep the cover on whenever nobody is in it: against the sun, the rain, the blossom and a curious child. The first-year service visit covers the rest.