Hard water deposits occur due to minerals in water. Stains vary in color, depending upon the type of mineral. Most stains can be removed by using acidic or abrasive cleaners, chlorine bleach or specialty cleaners designed for specific stains.
Identify the type of stain
White scale that forms on porcelain or tile is usually the result of lime in the water. Brown or red stains occur because of a build-up of iron. Most blue or green stains occur due to brass or copper additives.
Apply the correct cleaner
Different stains respond better to specific cleaners. Products containing sequestrants are best at cleaning away lime scale. Apply the product to the stain, allowing it to sit for a few minutes before wiping. Brass and copper stains respond well to white vinegar or lemon juice. Rust stains are best treated with products containing Oxalic acid. Oxalic acid is highly toxic. Follow all manufacturer's instructions when using it. If a stain is set in, an abrasive cleaner may be necessary to remove it. Be careful not to harm the surface when scrubbing.
Removal of water and the minerals it contains is the best way to prevent staining. Dry faucets, showers and sinks with a towel after use.