Your wooden tub actually requires very little maintenance. After some time the wood takes on a natural colour, without affecting the quality of the tub or the lasting qualities of the wood. A wooden tub which is always outside will change colour over the years, it will become greyer. Many people consider this a natural colour.
Never paint or lacquer the inside part of your hot tub as this prevents the natural wood’s ability to breath and control its humidity level. Lacquered wood does not absorb moisture: it cannot expand and may start to leak. The only recommended method of applying a protective layer is to apply linseed oil on the outside of your hot tub once or twice a year. This will protect the colour of the wood to some extent, without preventing the wood from its natural breathing.
It is mandatory to have the tub always filled with water to prevent the wood from drying out. When there is a risk of frost, you must empty the tub temporarily or keep the water circulating with the aid of an aquarium pump (for example). When the temperatures are high and the weather is exceptionally dry, it is necessary to keep the tub filled to the brim with water. If you do not do this, leakage could occur. Never empty the tub without allowing the heater to cool.
Leakage in itself is not a serious problem because the tub is made from natural material (wood) and the wood may warp during its lifespan. When leaks occur and are quite heavy, tightening the straps and keeping the tub wet will make the hot tub leak-free again.
It is recommended to clean inside of the hot tub with water from time to time. After you drain the water you can use a brush or a high-pressure cleaner. If the hot tub stands empty, do not cover it – air must circulate to prevent mould.
The hot tub must be placed on stable, flat and even ground. The foundation can be made of paving tiles, gravel or concrete. It is very important to make sure that water can drain away and air can circulate underneath the hot tub in order to avoid the formation of mould. If those requirements are followed, the bottom needs no special treatment.