The Hot Tub should be treated with linseed oil or wood supplement oil / wood glace on the outside every year.
Wood supplements should not be used on the inside.
It is recommended to clean the inner part with soap, soda supplements or similar supplements and a brush. This prolongs the life expectancy substantially from up to 10 – 15 years. The Hot Tub will absorb less water after a while. We know Hot Tubs which are between 40-50 years old and which are still in use.