The ugly brown spots on the bathtub and wash basin may be rusty, which is caused by many different reasons. Usually, rust is the result of water passing through rusty old galvanized pipes. If you have hard water, rust may be caused by iron and minerals that remain on the surface of your wash basin. However, in the final analysis, it doesn't matter how the wash basin gets those stain. The important thing is that it looks bad and should be cleaned up. Fortunately, removing these stains is easy.