Heatable plastic tank

A plastic tank contains a heating coil, the ends (3) of which are attached to a metal fitting (2) that passes through the tank wall (1) and provides a connection (12) with a seal for a heating fluid supply. The connection fitting (2) is encased on the inside of the tank with plastic by sintering to protect and seal it. An independent claim is also included for the method of manufacture, consisting of welding the fitting (2) to the coil end (3) to give an oil-tight joint, inserting the coil and fitting into the tank with a metallic mold, filling the mold with plastic powder and sintering with heat while rocking the assembly.