What is there to know about heating the hot tub with a wood-fired stove

What kind of wood should I use?

The best and most cost-effective wood is dry split birch (Nordic countries). When burning hardwood, you should use a separate acid-resistant ash pan. You can of course also use other types of wood. In general, the higher the density of the wood, the higher the calorific value. It is essential that the firewood is thoroughly dry.

How much wood is needed to heat the hot tub?

Depending on the time of year, 60-120 liters of dry birch wood (Nordic countries) are required to heat the hot tub.

What should you pay attention to when heating?

First, check if there is water in the tub! Even if you heated it up the night before, check the tub, nonetheless. If you want to get the water warm as quickly as possible, use good-quality dry firewood. Using the lid (better insulated) significantly reduces heating time. This is because there usually is a big temperature difference between hot water in the tub and the outside weather. Before you start firing, remove the ash from the ash pan and from the grate. Keep the fire high and add wood every 10-15 minutes so that the fire doesn’t go out as it heats up. Gravity makes the water circulate (hot water goes up and cold goes down), and that circulation slows down when the fire goes out. Re-igniting and getting the circulation going takes time.

How is the water heated?

The bathwater is heated with the wood-burning stove, so no electricity is required for heating. Haven’t said that there can be many different water heating sources such as gas heaters; electric heaters; wood pellet heaters and more. During heating, the stove must be full of water. When heated water becomes lighter and rises to the upper part of the stove, from where it flows through the circulation pipe to the bath. Cold-water present in the bath sinks to the bottom and from there flows through the circulation pipe to the stove.

How quickly does the bathwater heat up?

The rate at which the bathwater heats up depends on the power of the stove, the size of the bath, the quality of firewood, the outside temperature, and whether the lid is used. At an outside temperature of zero degrees, for example, a bath with 1450 liters of water heats up in about 2-3 hours. It is best to use dry wood split into small parts for heating. When using large pieces of damp wood, heating can take up to twice as long.