A system for fire protection comprising: a primary fluid; a secondary fluid; a normally closed piping network of sprinklers ; and a fluid control valve including a body having an inlet coupled to the primary fluid, an outlet coupled to the piping network of sprinklers and an inner surface defining a passageway between the inlet and the outlet , the body further including a port in communication with the passageway and located between the inlet and the outlet ; and a flexible member engaged with the inner surface by fluid pressure acting on the flexible member to dissect the passageway to define an inlet chamber in communication with the inlet for housing the primary fluid at a first pressure, an outlet chamber in communication with the outlet and the piping network of sprinklers so as to form a normally closed system to house the secondary fluid at a second pressure, the second pressure being substantially constant between the outlet chamber and the piping network of sprinklers and greater than atmospheric pressure; and an intermediate chamber disposed between the inlet chamber and the outlet chamber and in communication with the port ; wherein the inner surface includes an elongated seat member for engagement with the flexible member , the seat member defining a groove forming part of the intermediate chamber that is in communication with the port . a primary fluid; a secondary fluid; a normally closed piping network of sprinklers ; and a fluid control valve including a body having an inlet coupled to the primary fluid, an outlet coupled to the piping network of sprinklers and an inner surface defining a passageway between the inlet and the outlet , the body further including a port in communication with the passageway and located between the inlet and the outlet ; and a flexible member engaged with the inner surface by fluid pressure acting on the flexible member to dissect the passageway to define an inlet chamber in communication with the inlet for housing the primary fluid at a first pressure, an outlet chamber in communication with the outlet and the piping network of sprinklers so as to form a normally closed system to house the secondary fluid at a second pressure, the second pressure being substantially constant between the outlet chamber and the piping network of sprinklers and greater than atmospheric pressure; and an intermediate chamber disposed between the inlet chamber and the outlet chamber and in communication with the port ; wherein the inner surface includes an elongated seat member for engagement with the flexible member , the seat member defining a groove forming part of the intermediate chamber that is in communication with the port . a body having an inlet coupled to the primary fluid, an outlet coupled to the piping network of sprinklers and an inner surface defining a passageway between the inlet and the outlet , the body further including a port in communication with the passageway and located between the inlet and the outlet ; and a flexible member engaged with the inner surface by fluid pressure acting on the flexible member to dissect the passageway to define an inlet chamber in communication with the inlet for housing the primary fluid at a first pressure, an outlet chamber in communication with the outlet and the piping network of sprinklers so as to form a normally closed system to house the secondary fluid at a second pressure, the second pressure being substantially constant between the outlet chamber and the piping network of sprinklers and greater than atmospheric pressure; and an intermediate chamber disposed between the inlet chamber and the outlet chamber and in communication with the port ; wherein the inner surface includes an elongated seat member for engagement with the flexible member , the seat member defining a groove forming part of the intermediate chamber that is in communication with the port . <EOS>