An anode is a magnesium rod inside your hot water tank and is the only thing that protects your tanks steel cylinder from severe corrosion resulting in premature tank failure. Every hot water tank comes with one and they usually only last 2-5 years. Once your anode is depleted there is nothing to stop the destructive effects of corrosion on your tank. Keep the tank you’ve got and look after it. Replace the anode and it will l last up to 3 times as long. If your hot water tank is over 4 years old then you need to replace the anode now.