Abstract: A fuel-fired water heater has a combustion chamber disposed beneath the storage tank portion of the water heater. The bottom side wall of the combustion chamber is defined by an annular perforated wall structure with a perforated mounting plate structure being removably secured to the underside of the wall structure over the central opening therein. A burner and associated pilot/thermocouple assembly are secured to the upper side of the mounting plate and project upwardly into the combustion chamber, with the piping and wiring of the burner and pilot/thermocouple assembly extending externally beneath the combustion chamber, outwardly through a side wall access passage, and then turning upwardly along the outside of the water heater for connection to a thermostatic fuel valve. To remove the bottom plate-mounted burner and pilot/thermocouple assembly the fuel supply piping must first be decoupled from the thermostatic valve, thereby assuring that the access plate cannot be removed while the burner is firing.