Things You'll Need
Long-handle scrub brush
Vinyl siding is susceptible to stains just like any other housing material. Hard water stains are ugly, but not impossible to remove. Simple bleach solutions applied to the stain and then brushed away, will return the vinyl to a state close to its original look. With the addition of a pressure washer to blast away any remaining hard water residue makes it appear almost new.
Use a hose to spray the outside surface of the vinyl siding until it is dripping and wet. For large walls of siding, it may be best to work in smaller, more manageable sections. Vinyl siding isn't porous, so water will not absorb into the surface. This also speeds drying time.
Mix a bleach and water solution in a pump sprayer. The ratio is one part bleach to three parts water. Stir it thoroughly to get the bleach fully diluted by the water.
Spray the siding with the bleach solution and use a scrub brush on a long handle to lightly buff the surface. Use the pump sprayer to thoroughly coat the vinyl surface, and allow it to remain for a few minutes on the surface to work on the stain.
Use a pressure washer to blast the bleach solution and broken down stain from the surface of the siding. Use a medium setting and move the spray back and forth in a horizontal motion. Scrub stubborn stains with the brush and rinse again with the power washer.
Move to the next section of vinyl and repeat the process until all the stains are removed. If necessary, reapply the bleach solution and repeat the scrubbing and rinse until it is gone.
Use plastic sheeting to cover any plants or flowers to keep the bleach from damaging them.
Be sure all windows and doors are closed before spraying. To protect yourself from the bleach spray, wear old clothing and safety glasses.