The buildup is the result of mineral deposits. You can remove the unsightly build up with something that you probably have in your kitchen pantry. Pour a cup of vinegar into a plastic bag. Secure the bag around the shower head or faucet using a twist tie, and allow it to remain in place overnight. The next morning, remove the bag and gently scrub away any remaining deposits with an old toothbrush. Some faucets allow you to remove the aerator so that you can leave it to soak in the bag overnight.