The present application relates to a fuel flow system. In particular, the application relates to a fuel flow system for an aircraft. The fuel flow system has a fuel conduit having a fuel inflow and a fuel outflow along which a fuel/water mix is configured to flow from the fuel inflow to the fuel outflow. The fuel conduit is fluidly communicable with a fuel tank. A peripheral conduit surrounds at least part of the fuel conduit. A water-permeable member is disposed between the fuel conduit and the peripheral conduit. The water-permeable member enables water from the fuel/water mix to flow through the water-permeable member from the fuel conduit into the peripheral conduit, but at least substantially prevents liquid fuel from the fuel/water mix from doing so.