A differential dry pipe valve is provided having a body including an inlet chamber having an inlet port, an exit chamber having an exit port, and a gasket flange positioned between the inlet and exit chambers facing the exit port, the inlet and exit ports being substantially aligned. The valve also includes a gasket attached to the gasket flange and an openable cover hingedly attached to the body. The gasket has an inner water lip in fluid communication with the inlet chamber and an outer air lip surrounding the water lip. The spacing between the water lip and air lip varies. The air and water lips are coaxial. The cover is configured to be sealingly engaged with the seal when in a closed position and to be sealingly disengaged in an open position when the pressure in the exit chamber is lower than the pressure in the inlet chamber. When the cover is in the open position, a direction of a path between the inlet and exit ports is substantially unaltered.