United States

Ohku

Concrete soaking tubs heated by an external wood-fired stove, no electricity needed.

Ohku calls its tub the first wood-fired concrete hot tub. The freestanding concrete shell is shaped like a Japanese ofuro, so it holds as little as 60 gallons yet fits one to four people, and it sits on a floating cedar platform. An external stainless steel wood-fired heater keeps ash out of the water and, per the maker, brings the tub up to temperature in under an hour. There are no chemicals to manage: soak in fresh water and drain it onto the garden afterward.