A combined water drain and diluent gas purge valve routes fluid from the anode side of a fuel cell to the cathode inlet. When a purge of diluent gas is requested, the valve opens, draining any liquid present in the sump of a water separation device, for example. After the liquid has drained, the diluent gas is purged. An anode bleed model using fuel injector feedback can determine the amount of gas exiting the valve, and can request the valve to close once the required amount of diluent is purged. During operation, an amount of hydrogen may exit the valve. Hydrogen passing through the valve can be catalytically consumed once it reaches the cathode electrode, causing the cathode exhaust, and the fuel cell exhaust to have a reduced hydrogen content.