the cylindrical center section 22 and extends from the convex top 24 the top extension 34 is closed at its top by a top plate 36 the top plate 36 is preferably a disk of stainless steel which is bolted to a flange on the top extension 34 the top plate 36 is provided with threaded holes into which are mounted a temperature and pressure relief valve 38 a hot water outlet 40 a cold water inlet tube 42 a float switch 44 and a heating element 46 the temperature and pressure relief valve is conventional the hot water outlet tube is also conventional and is simply a short length of pipe extending upwardly from the top plate 36 the cold water inlet tube is conventional and comprises what is generally known as a dip tube extending downwardly into the plastic tank 14 and a short length of pipe extending upwardly from the top plate 36 the float switch is also conventional and comprises a commercially available float switch which reacts to the presence or absence of water at the top of the tank and is used to prevent electric current from flowing through the heating element when the tank is not full the heating element is also conventional and comprises an electrical resistance heating element.