A little known factor that determines how long your water heater lives or dies depends on the condition of its magnesium anode. This component is the vital key to the rust protection of the tank. You can easily check the state of your anode and get many more years of service from your heater by making a simple replacement.

Follow this guide to learn more about the hidden world of magnesium anodes and how to go about checking and replacing them.

What is a Magnesium Anode?

The anode is a magnesium rod which surrounds a steel core wire and is screwed into the top of the water tank. Residential tanks will have either one or two of these anodes. Those with two will usually be covered with a much longer warranty period. Larger tanks used for commercial premises may have up to five anodes.

How do they Work?

The magnesium anodes work on a principle similar to electrolysis. When a meal surface comes into contact with electrolytes in water, an electrochemical reaction, which we know as corrosion, takes place. This process begins to disintegrate and weaken the structure of the metal as it begins to return it to its natural state as an ore.

In order to protect the metal water tank from corrosion, a highly active metal: magnesium is used. It protects the less electrochemically active metal of the tank surface. In effect the magnesium "surrenders" itself and is "consumed" in place of the metal it protects. This is the how the term "sacrificial anode" originated.

How to Check Your Anode

Follow these simple steps to assess the state of your water heater anode.

• Shut off the cold water valve and turn off the power (for electric heaters) or gas.

• Remove the vent pipe (if there is one) to give you more working room.

• Turn on a hot water tap in the house to relieve pressure

• Release about 4 or 5 litres from the drain valve

• Locate the anode, usually on the back of the tank, a few centimeters out from the flue.

• begin to carefully loosen the anode with a socket wrench. Be prepared to work at it, as original anodes are usually installed very tightly.

When you have successfully removed the anode inspect it for signs of wear. If it appears to be splitting or more than about 10 centimeters of core wire is exposed it needs to be replaced.

However, if most of the metal is intact and you don't use water softening chemicals the anode will last for a few more years.

Alternative Procedure

If you come across difficulties in removing the old anode, there is another alternative. You can leave the anode in place and install a combination anode rod. You simply need to disconnect the hot water side plumbing. Use a pipe wrench to remove the old nipple and insert a new rod. Use pipe seal tape rather than screws as it will be much easier to remove in future. As far as maintenance goes you will only need to check back in another four years or so.

Sourcing a New Anode

Anode rods are readily available online. They may be manufactured from magnesium, aluminium or zinc. Magnesium and aluminium are the most common metals used in water heater anodes. Although aluminium anodes are the least expensive they may not be as efficient. There is also the concern about aluminium and some of its possible adverse effects on health.

Should you have the slightest doubt about your ability in dealing with these anode replacement tasks it is essential to consult the professionals. Messing with electricity or gas are dangerous activities and water pressure gone wrong can produce disastrous consequences in a household.