Wood-sided hot tubs come in two forms. They can enclose an acrylic hot tub, or the hot tub can be completely wooden. With either form of hot tub, it is necessary to treat the outside so the wood resists weathering and rot from the constant contact with water. The type of treatment you select depends on the type of wood the manufacturer used in constructing the siding.
Fill a bucket with warm water. Add a household disinfectant according to the package directions. Dip a soft-bristled scrub brush into the solution and gently scrub the wood sides of the hot tub, following the grain of the wood. Rinse the wood with a garden hose and let it air dry.
Select a sealer for your wood-sided hot tub. Some woods, such as cedar, require a species-specific sealer. If you are unsure what kind of wood you have, consult the hot tub manufacturer. You can also select a coloured stain as a sealer, if your wood's colour has faded. Make sure the sealer is waterproof and has a UV protectant.
Shake the can of sealer to incorporate any pigmentation. Open the can and dip a paintbrush into the sealer.
Apply the sealer in long, even strokes that follow the grain of the wood. Overlap the edges of your strokes to prevent brush strokes from showing when you are done. Let the sealer soak according to the package directions. Wipe off any excess sealer with an old cloth.
Repeat the sealing once or twice a year, depending on the severity of your local weather conditions.