Allow the tank to cool completely. Douse the screw thread area where the heater is fixed into the tank with WD40 or similar and leave overnight to soak through. Then if safe and practical heat the tank around the immersion fixing with a hot air gun in an endeavor to expand the metal of the tank and break the bond with the immersion heater. Use a proper proprietary spanner to unscrew the heater element, lengthening the handle if you can in order to increase the moment arm and therefore the effort applied to unscrew the element. Be careful not to twist the tank fitting as this will damage the tank. If it does not unscrew readily then repeat the WD40 and heat treatment. Hope this works - it did for me!
Rod T., March 2009
