Tenspa all stoves are a high quality water heaters designed specifically for hot tubs. It circulates water using the principle “thermosiphon”. Hot water rises and creates low pressure, which sucks water from below. Hot tub stoves, made from high-quality stainless steel, stand out for their exceptional thermal efficiency and long-lasting durability.

It eliminates the need for a circulating pump and electricity, making it possible to heat the water in a hot tub with the heater placed externally. A big advantage is that there will be more space in the tub, which in turn means a smaller model can be selected. The stainless steel body surrounding the firebox is actually a double-wall water-jacket, making the entire firebox a heat-transferring surface.

The wood burning heater utilizes a sophisticated heat exchange design for efficient water heating. The stainless steel stove body surrounding the firebox is a double-walled water-jacket with a 1.5-inch space between, making the entire firebox (except the front) a heat-transferring surface. Additional heat transfer takes place in a water-filled baffle tube that runs horizontally through the firebox. The baffle deflects the path of the fire, so it gives up more heat into the water jacket before going up the chimney.

Heat is easily controlled by adjusting the air draft control for heating the water and maintaining the water temperature.

• Chlorine content: max 3.5 mg/l (ppm)*
• pH value: 7.2–7.6
• Alkalinity: 60–120 mg/l (ppm)
• Calcium hardness: 100–300 mg/l (ppm)
• Iron: max 0,1 mg/l (ppm)*
• Copper: max 0,2 mg/l (ppm)*
• Manganese: max 0,05 mg/l (ppm)*
• Phosphorus: max 0,01 mg/l (ppm)*
• Nitrate: max 50 mg/l (ppm)*
• Chloride (salt) content: max 250 mg/l (ppm)
• Chloride (salt) content: max 35 000 mg/l (ppm) – titanium for salt water

• The stoves are specially designed for the hot tubs or small pools
• Maximum acceptable water temperature in the hot tub is 45 degrees
• It is not allowed to close the input and output pipes of the stove during the burning and until the stove is cooled down
• It is not allowed to create extra pressure in the stove
• It is not allowed to let the water freeze in the stove
• It is not allowed to let the water freeze in the hot tub
• It is not allowed to use the stove without water inside the hot tub

Correct and incorrect connection of the external stove

• The external heater and outdoor hot tub must be placed on a flat, solid surface.
• It is important that the connection hose at the top connects slightly (with a little angle).
• The lower stove connection hose can be connected evenly.

CAUTION! Never burn the stove without the required amount of water in the hot tub. Otherwise, you may burn the stove and hot tub.

To ensure the best quality and durability, we produce and use stainless steel stoves for our Tenspa hot tubs. For the heaters we use only AISI 316 or AISI 304 grade stainless steel. Stainless steel is extremely durable and withstands various agents and chemical substances used to clean the water of the hot tub. A stainless steel stove is also more user-friendly. Should it happen that you forget some burning coals in the stove after using the hot tub but have already emptied the tub of water, the stove will not be damaged so easily. For a stove made of aluminium, the damage that occurs to the heater with such a human error is irreparable. In addition, the service life of an aluminum stove is shorter and it takes less time for them to lose their beautiful appearance and durability.

There was a period when aluminum heaters became very popular because it was said that they conducted the heat better and got the job done quicker. By now, it has been proven untrue. Tenspa stainless steel stoves have been designed by the engineers to direct 100% of the energy produced by heating to get the water hot.