EJK maxi heaters are designed for heating water in open and closed metal tanks, including enamelled domestic hot water tanks. In those tanks, in which anti-corrosion cathodic protection system is using magnesium anode or external current anode, heating elements should be partially insulated electrically from tank walls. Thanks to this, the electrochemical potential difference between heating elements made of copper or special stainless steel and the tank made of carbon steel is partially equalized in a tank filled with water. This way the durability of heating elements and the life of the magnesium anode are increased significantly.