A fuel cell system that routes anode effluent from one fuel cell stack to the anode side of another fuel cell stack to consume unused hydrogen in the production of electricity is disclosed. The routing of the anode effluent from one fuel cell stack to another is accomplished by providing flow paths that connect the anode sides of the various fuel cell stacks together. The flow paths contain valves that are operable to selectively block flow through the various flow paths as desired. Optionally, the flow paths can be operated free of any valves. Methods of operating such fuel cell systems are also disclosed.