An automatic valve includes a body configured to receive a piston axially therein, the piston being movable within the body between a first axial position in which the piston is configured to seal a valve opening when pneumatic pressure is applied to the piston and a second axial position in which the piston is configured to be withdrawn from the valve opening such that a fire suppression agent can enter the valve body through the valve opening, wherein the piston includes a channel longitudinally therethrough and a check valve positioned within the channel such that fluid can enter the check valve in a first longitudinal direction but not in a second longitudinal direction.