A dump valve (74) is provided for selectively inflating and deflating an air cushion (40) on a bed (10). The dump valve comprises an elongated housing (78) having an interior region (80) extending along a longitudinal axis (110) and is mounted to a bed deck (18) so the axis is angled relative to the deck. A connector (90) is coupled to a first end (114) of the housing to couple the housing to an air supply. A piston (88) in the interior region can slide between first and second postitions. The first position permits air to pass from the air supply, into the interior region, and through a central opening (104) to inflate the air cushion. The second position blocks air flow from the air supply into the housing and permits air to pass from the cushion, through the central opening, and through an open second end (116) of the housing to deflate the cushion.