Hard water can leave spots and flakes on anything with which it comes into contact. This is due to the fact that this type of water has a higher concentration of minerals such as magnesium and calcium. If you have polished brass that acquires hard water spots (such as brass bathroom fixtures), you can remove them quite easily. You can save yourself money by using inexpensive, gentle household products for treating this type of problem.
Pour some white vinegar onto a clean cloth.
Wipe down the brass with the cloth to remove water spots.
Rinse the brass and dry it with a lint-free cloth.
Cut one lemon in half and sprinkle salt on one of the halves.
Rub the salted lemon over the brass to return its lustre.
Buff the brass dry and shiny with a clean, lint-free cloth.