A valve assembly can include a housing, which can define a first fuel input for receiving a first fuel from a first fuel source and a second fuel input for receiving a second fuel from a second fuel source. The housing can define a first fuel output for directing fuel toward a control valve, and can define a third fuel input for receiving a portion of either the first fuel or the second fuel from the control valve. The housing can define a first egress flow path and a second egress flow path, each for directing fuel to the burner. In certain embodiments, the apparatus includes a valve body configured to selectively permit fluid communication between the first and second inputs and the output and between the third input and the egress flow paths.