From outside it is recommended to protect a hot tub with wood care products (oil, glaze, wax) 1-2 times per year. If necessary you can clean the hot tub also with a pressure washer, with brush and water etc. From inside it`s not allowed to treat the hot tub with wood care products. From inside the timber must breathe and absorb the water. From inside it is recommended to clean the hot tub just with regular water from time to time.