'U' shaped or rod type heating elements are mounted in a heavy flange, elements are sheated in copper, steel or alloy to resist chemical action with appropriate heating surface watt, densities normally required. The flange, is welded to one end of a thick wall pipe or heating chamber. Threaded inlet, outlet and mounting legs are welded to the chamber, at end opposite the flange, a closure with centered drain tap, terminalwiring area is enclosed. Completely insulated chamber and built in thermostat is also available if suitable to requirement.