The Water Heater Anode Rod
The role of the sacrificial anode rod
The anode rod is the most important factor in determining the life of your water heater. An anode rod is a steel core wire surrounded with one of three different metals. These metals include aluminum, magnesium, and zinc. The rod is screwed into the top of your water heater and protects your water heater from rusting. When the tank is filled with water the anode rod sacrifices itself to protect the exposed steel of the water heater, through a method called electrolysis. Electrolysis happens when there are two pieces of metal connected inside of water, the process makes the anode rod corrode in place of the exposed steel in your water heater. During this process the more noble (less reactive) metal will corrode over the less (more reactive) noble metal. Aluminum, magnesium, and zinc are all much less noble than steel, meaning they will corrode before the steel, which is why they are used for anode rods.
Anode Rod Problems
The anode rod is designed to corrode in place of your water heater lining, when the rod has been completely corroded it no longer protects your water heater. The picture above shows what an anode rod looks like before installation (top) and what an anode rod looks like when it is completely depleted (bottom). A typical anode rod will last about 4-5 years but it depends on the amount of water traveling through your water heater. A water softener also shortens the life of your anode rods significantly. A depleted anode rod can and does cause your water heater problems. The first problem you can expect to encounter with a bad anode rod is the rusting of your water heater. If your water heater rusts you will most likely need to replace it, which will cost you much more than replacing an anode rod. Another problem you may encounter is having the anode rod break off and fall to the bottom of your water heater. The broken off rod will bounce around in the water heater anytime water passes through it, which will destroy the lining of the water heater very quickly. This creates cracks in the glass lining of the water heater which will drastically shorten your water heaters life. There is no question, failure to replace your anode rods in a timely fashion, will shorten your water heaters life.
Aluminum anode rods are best for places with hard water. The aluminum rod will withstand harder water than any other type. Aluminum may be a health problem, so to be safe you may not want to drink hot water and make sure to run some cold water through the faucet spout before drinking the water. Keep in mind, our sodas come in aluminum cans too.
Magnesium anode rods are the most common type of anode rod. They are used in places where water is softer. They do not last very long when you have hard water, a couple years at best. This is the main reason water heaters don't last long after the anode rod is eaten up.
Zinc anode rods are really just aluminum anode rods with a small portion being zinc. The ratio of zinc to aluminum is 1:10. The reason zinc is added is to combat any sulfur smell coming from the water. A new water heater is never installed with a zinc anode rod already in it, but it is a good upgrade if you experience rotten egg smell coming from your hot water.