A dry/deluge valve for an automatic sprinkler system. The valve includes a main chamber having an input port for receiving fluid from a supply line and an output port. A clapper assembly is installed in the main chamber for sealing the input port. The clapper assembly includes a threaded valve seat configured to be screwed into a wall of the main chamber, so as to be in communication with the input port. The assembly further includes a collar configured to receive the valve seat, wherein the collar is held in position by the valve seat. A clapper configured to seal the input port, in cooperation with the valve seat, is hinged to the collar, and a lever also is hinged to the collar and is movable between a first position in which the clapper is held closed by the lever and a second position in which the clapper is allowed to open. The dry pipe/deluge valve further includes a sensing chamber having components responsive to a control pressure of the sensing chamber, the components being in communication with the lever to move the lever between the first position and the second position.