Abstract: Water produced as a by-product of the electrochemical reaction in a fuel cell is treated so as to enable its use to produce, in a fuel conditioning subsystem including a steam generator and raw hydrocarbon fuel reformer, fuel for delivery to the fuel cell. The water conditioning system includes a novel deaerator wherein fuel cell waste heat is employed to heat water produced in the fuel cell to remove dissolved gases therefrom. The water treatment system also includes a cooler for reducing the temperature of the "deaerated" water prior to its delivery to a filter and demineralizer; the water being delivered to the boiler of the steam generator subsequent to passage through the demineralizer.