For most water heaters, the anode rod is attached to the hot water outlet of the water heater. If you are facing the front of the water heater (where the labels are), the hot water outlet is on the left hand side. The anode rod is often referred to as a "sacrificial rod".   Most water is rarely "pure". It can contain oxygen, magnesium, fluoride, chlorine and suspended particles. These components, in the concentrations in your water, are usually not bad for you. However, they do contribute to the taste and smell of the water. They also impart a slight conductivity to the water. Through an electrical process called electrolysis, this conductivity will eventually (over a long period of time) cause most metal to rust or corrode. When the water is heated, this electrical process can be accelerated.   Most water heaters are made of a steel tank with a porcelain enamel (glass) lining. However, due to production and assembly methods, it is not always possible to completely cover the inside of the tank. Therefore it is important to provide metal that can be consumed by the electrical process. This is where the sacrificial anode rod comes in. By acting as a lightning rod for the corrosion process, the anode rod draws the harmful electrolytic process away from the water heater tank and focuses the corrosion on the anode rod. Water heaters need this sacrificial anode rod to ensure that the electrolysis does not affect the tanks.