The anode is a magnesium rod that is located inside the boiler tank. When water is heated, oxygen is actively released from it, which can cause corrosion of the tank walls. The anode actively absorbs oxygen released from the water and prevents damage to the tank walls, gradually dissolving. If the anode is allowed to completely dissolve, the boiler tank will rapidly become unusable and may leak.The anode should be replaced once a year. The cost of the anode is not included in the cost of service and is paid separately.