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Water Heater Anode Rods

There is nothing quite like that warm shower in the morning or after a hard day's work. Virtually, everybody, myself included, takes hot water for granted. We use it throughout the day for bathing, washing dishes, clothes, etc. It has become a necessary element of our lives.


Water heaters are very simple mechanical items. They have virtually no moving parts. Electric hot water heaters have very small switches that turn the current on and off automatically to each heating element. Gas hot water heaters have small parts within the gas valve that control gas flow when it is necessary for the burner to cycle on or off. Rarely do these moving parts fail. Tank corrosion is the #1 cause of water heater failure. High pressure failures are also becoming a problem as well. Both of these problems can be somewhat controlled. You simply need to consider several alternatives before you install your next hot water heater.

Yum ! Yum!

Corrosion within hot water heaters can be caused by water acidity, electrical conductivity, dissolved oxygen, and temperature. Water can react chemically with metal parts inside of the water heater. Acidic water can actually eat away at the metal. This corrosion process is accelerated with temperature. So as we heat the water for our usage, we actually can hurt the tank!


Approximately 40 years ago, water heater manufacturers began lining the steel tanks with a thin coating of glass. This coating isolated the steel tank from the corrosive water. However, every inlet and outlet port of the tank has metal connectors which are not glass coated. These areas are subject to corrosion. Also, gas hot water heaters have an additional problem. Every time the burner turns on it heats the metal at the bottom of the tank. This heat causes the metal to expand. When the burner shuts off, the metal contracts. This constant expansion and contraction weakens the metal at the bottom of the tank. It can also cause micro fractures in the glass lining. Water can then get in contact with the bottom of the tank and begin the corrosion process.

Dissolved Minerals = Lost $

Have you ever used distilled water in your clothes iron? Did you know why? Regular tap water often has huge amounts of dissolved minerals. These dissolved minerals can clog up your iron in no time. The process is accelerated because of the heat produced by the iron.

Distilled water, on the other hand, is virtually pure water. The distillation process removes the dissolved minerals. However, it also loses its taste. Dissolved minerals give water its taste. In addition, these minerals also permit water to conduct electricity. Pure water (100 percent H2O) is actually an insulator. Electricity will not pass thru it easily. However, water which contains dissolved minerals is a great conductor. Electricity passes readily thru this type of water. That's why household water (as well as ocean, river, lake, etc. water) poses an electrocution hazard. Almost all water contains dissolved minerals.

Anodes - The Staff of Life

Depending upon the source of the water supply, the dissolved mineral content can be high, medium, or low. Also, there will be different minerals present. The heating of water within a hot water heater and the motion of the water cause tiny electrical currents to be generated within the water heater. These electrical currents start to eat away at any exposed metal. That's why water heaters have anode rods as a part of their construction. These anode rods are made of magnesium. The magnesium attracts the electrical current and corrodes more easily than the steel tank. However, if the anode rod completely dissolves, the electricity within the tank will begin to look for some other metal. That's why you need to check your anode rod periodically.

Many people know the difference between hard and soft water. Hard water is water that has a high amount of dissolved minerals. When hard water is heated, some of these minerals can precipitate out of the water and form a scale on the inside of the water heater. This scale can flake off and begin to collect on the bottom of the tank. This lowers the efficiency of the water heater by acting as a barrier to the flow of heat from the burner to the water. This scale can also corrode heating elements on electric hot water heaters in a very short period of time. Friends of mine have had to replace electric heating elements every 3 months because of this problem.


Since we're talking about electricity, let's finish with electrolysis. Iron is the primary metal used to construct hot water tanks. You can see this iron at the top of the tank where the hot and cold water pipes attach to your heater.

Often rookie plumbers or homeowners simply install a copper male adapter into the female iron tank fittings. This metal to metal contact of two dissimilar metals can lead to corrosion.

These connection points need to be isolated "electrically" from the water pipes. There are several different connectors made for this purpose. I, personally, choose to use di-electric unions. Good Luck!

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