Fuel cell system and related operating method

A fuel cell system and a related operating method are disclosed wherein a fuel-line water recovery tank 19 collects water discharged from a fuel electrode of a fuel cell 1, and an air-line water recovery tank 13 collects water discharged from an air electrode of the fuel cell 1. Disposed downstream of the air-line water recovery tank 13 is a combustor 35 that combusts fuel gas expelled from the fuel-line water recovery tank 19, and air. In the presence of discrimination that water in the fuel-line water recovery tank 19 is to be discharged, a controller 7 opens a fuel-line water discharge valve 23 and allows collected water to be discharged.