Pressure reducing valve for an automatic fire extinguishing system comprising a. valve housing having a longitudinal axis i. with an inlet opening for connecting the pressure reducing valve (5c;5f) to a pressure container in which an extinguishing medium is supplied under high pressure (p H) ii. with an outlet opening for connecting the pressure reducing valve (5c; 5f) to an extinguishing medium output device and iii.with a flow channel arranged between the inlet opening and the outlet opening, b. a pressure regulating piston (24c; 24f) which is displaceable in the valve housing along the longitudinal axis between an open position and a closed position, c. a first sealing element (19c; 19f, 51) arranged along the flow channel for sealingly bearing against the pressure regulating piston (24c; 24f) in the closed position, d. a force accumulator element for exerting an opening force (F 1) on the pressure regulating position (24c; 24f) for the displacement thereof into the open position, e. wherein in the closed position of the pressure regulating piston (24c; 24f) the first sealing element (19c; 19f, 51) separates a high-pressure chamber facing the inlet opening in fluid-tight manner from a low-pressure chamber of the flow channel facing the outlet opening, f. wherein the extinguishing medium is supplied in the high-pressure chamber with high pressure (p H) and in the low-pressure chamber with low pressure (p N), and g. wherein the extinguishing medium creates a closing force (F 2) acting opposite the opening force (F 1) on the pressure regulating piston (24c; 24f) in order to move the latter into the closed position, h. the pressure regulating piston (24c; 24f) is arranged in the open position spaced from the first sealing element (19c; 19f), characterised in that i. a guiding/sealing portion (25c; 25f) of the pressure regulating piston (24c; 24f) has a widened bowl-shaped portion arranged opposite a base portion (28c; 28f), j. a fluid flow guide element (15c; 15f) is provided adjacent the inlet opening to control the fluid flow along the flow channel, wherein the fluid flow guide element (15c; 15f) has a central fastening portion designed concentric with the longitudinal axis and arranged centrally in an immersion recess (18c; 18f), wherein the immersion recess (18c; 18f) is an annular groove into which the pressure regulating piston (24c; 24f) can project with the bowl-shaped portion to sealingly bear against the first sealing element (19c; 19f), k. the first sealing element (19c; 19f) bears against an inner cylindrical sleeve face of the pressure regulating piston (24c; 24f) arranged in the closed position. a. valve housing having a longitudinal axis i. with an inlet opening for connecting the pressure reducing valve (5c;5f) to a pressure container in which an extinguishing medium is supplied under high pressure (p H) ii. with an outlet opening for connecting the pressure reducing valve (5c; 5f) to an extinguishing medium output device and iii.with a flow channel arranged between the inlet opening and the outlet opening, i. with an inlet opening for connecting the pressure reducing valve (5c;5f) to a pressure container in which an extinguishing medium is supplied under high pressure (p H) ii. with an outlet opening for connecting the pressure reducing valve (5c; 5f) to an extinguishing medium output device and iii.with a flow channel arranged between the inlet opening and the outlet opening, b. a pressure regulating piston (24c; 24f) which is displaceable in the valve housing along the longitudinal axis between an open position and a closed position, c. a first sealing element (19c; 19f, 51) arranged along the flow channel for sealingly bearing against the pressure regulating piston (24c; 24f) in the closed position, d. a force accumulator element for exerting an opening force (F 1) on the pressure regulating position (24c; 24f) for the displacement thereof into the open position, e. wherein in the closed position of the pressure regulating piston (24c; 24f) the first sealing element (19c; 19f, 51) separates a high-pressure chamber facing the inlet opening in fluid-tight manner from a low-pressure chamber of the flow channel facing the outlet opening, f. wherein the extinguishing medium is supplied in the high-pressure chamber with high pressure (p H) and in the low-pressure chamber with low pressure (p N), and g. wherein the extinguishing medium creates a closing force (F 2) acting opposite the opening force (F 1) on the pressure regulating piston (24c; 24f) in order to move the latter into the closed position, h. the pressure regulating piston (24c; 24f) is arranged in the open position spaced from the first sealing element (19c; 19f), characterised in that i. a guiding/sealing portion (25c; 25f) of the pressure regulating piston (24c; 24f) has a widened bowl-shaped portion arranged opposite a base portion (28c; 28f), j. a fluid flow guide element (15c; 15f) is provided adjacent the inlet opening to control the fluid flow along the flow channel, wherein the fluid flow guide element (15c; 15f) has a central fastening portion designed concentric with the longitudinal axis and arranged centrally in an immersion recess (18c; 18f), wherein the immersion recess (18c; 18f) is an annular groove into which the pressure regulating piston (24c; 24f) can project with the bowl-shaped portion to sealingly bear against the first sealing element (19c; 19f), k. the first sealing element (19c; 19f) bears against an inner cylindrical sleeve face of the pressure regulating piston (24c; 24f) arranged in the closed position.