Most dirt on a vinyl side railing can be washed off with water. You can clean most of this dirt off by spraying it with a garden hose. In most cases, the gloss of the vinyl was being dulled by a thin layer of dust rather than debris that is affixed tightly to the surface of the vinyl. A pressure washer can remove dirt that is slightly more stuck on than using a garden hose, but using one is optional. Most homeowners do not need to regularly wash off a vinyl railing because any recent rain cleans off a lot of the dirt that could be removed using a garden hose. You mostly need to wash areas of the railing that do not regularly get hit by rain, such as sections of railing located under an overhang of the roof.
Spraying the rail with water might not be enough to remove all of the dirt on it. However, if it is dirt, rather than a stain, you should be able to clean it using a detergent or household cleaner. Most nonspecialized cleaners work on vinyl. Almost any cleaner or detergent should work effectively to remove any remaining dirt on the railing. If you have mildew or mold on the railing, you should use bleach instead.
While most of the gloss loss on a railing can be attributed to dust, oils deposited on the surface of the vinyl can also dull the luster. The oils might be able to withstand the detergent or household cleaner and continue to remain on the railing. Mineral spirits can be used to remove any remaining oils from the surface of the vinyl. You do not want to leave mineral spirits on the railing for an extended period of time. Wipe the oil stain with a cloth covered in mineral spirits until it is gone. Once the stain has been removed, immediately wash the area where you used the mineral spirits with water.
Rust stains can occasionally appear on vinyl railing, which creates dull, brownish red stains on the surface. The source of the rust usually comes from gutter runoff that leaks onto the railing. Rust dissolves into the water as it goes through the gutter. When the water evaporates off the railing, it leaves the rust behind. Most cleaners do not remove rust from vinyl. Toilet cleaners work very effectively to remove rust stains from a vinyl railing. Wipe the rust stains using the toilet cleaner. Once you have removed the rust stains, immediately wash the area using fresh water to remove any remaining residue from the cleaner.