Many water heaters have a glass lining that is designed to protect the metal parts from corroding. Eventually, the coating may crack. For this reason, the tanks are fitted with anode rods which serve as the second defense against rust because they work by pulling corrosive elements from the water. Since all metals fall in the class of galvanic scale of reactivity, whenever two of them are connected physically in water, the less reactive one will disintegrate to protect the other. Typically, steel tends to corrode faster than copper, so when oxidation occurs in the anode rod, it fails to do its job, causing the tank to rust.
If you discover that your water heater is giving out rusty water, it could be an indication of the tank rusting away, which may soon be followed by leakage. When the walls of the tank start to rust and the rod fails, sediments form at the bottom and could alter the performance of water heaters. It is, therefore, essential to hire an expert to clean and replace the anode to prevent the buildup of rust. Read more on this article: http://bit.ly/2iGhWjE