A mandrel in production tubing within a well has a side pocket with an inlet port for connection to an upper control line segment that extends upward alongside the production tubing. An outlet port is below the inlet port for connection to a lower control line segment extending below the pocket. A filter assembly is lowered through the production tubing into the pocket. A valve at a lower end of the pocket is movable from a closed position closing the outlet port to an open position opening the outlet port. A probe mounted to a lower end of the filter assembly engages and pushes the valve from the closed position to the open position while the filter assembly is being seated in the pocket.