The principle of heating water in a samovar type tank. In the process of burning wood, the chimney is heated. At the same time, the water in the tank is heated. The tank provides heating of the water to a temperature of 70–75 ° C by the time the temperature in the steam room reaches 90 ° C and the time the brooms are steamed. The area of contact between the hot surface of the chimney and the water as it is consumed decreases, which makes it possible to prevent intense boiling of water and significant steam from the tank to the steam room when the furnace is in the temperature maintenance mode.