A screen system having first and second side members, each having a locking gear reversibly movable from a locked position to an unlocked position. A screen is coupled to the side members. The screen has openings and is rotatable from a closed position to an open position. The screen is engagable with the locking gears to preventing the screen from rotating from the closed position to the open position. A trigger plate is movably coupled to the screen, rotates from a first position to a second position and is engagable with the locking gears to prevent the locking gears from moving from the locked position to the unlocked position. The trigger plate disengages with the locking gears when water flows against it, allowing the locking gears to move from the locked position to the unlocked position and the screen to rotate from the closed position to the open position.