If your cold water appears rusty all of a sudden, it is probably due to a work crew in the area. They may be isolating an area to do emergency repairs, or opening an area hydrant. This stirs up sediments in the water mains. The rusty water is harmless and will clear up all by itself within a couple hours. Running the water in your faucet will not make this clear faster. If after several hours, or if a rusty condition in your cold water persists, call the water quality laboratory at 847-931-6158.