the first exemplary embodiment of a pressure reducer according to the invention has a housing 10 , which is implemented as a slanted seat housing with an inlet port 10 a and an outlet port 10 b . the outlet port 10 b includes a connection for a pressure gauge which is closed with a cover 80 . a seal 130 is inserted between the cover 80 and the housing 10 . a valve insert is inserted in the housing 10 , or more specifically in an connecting socket 10 c of the housing , with the valve insert composed of the parts indicated with the reference symbols 2 to 70 , 90 to 120 , and 140 to 160 . the valve insert includes a sleeve 30 . the sleeve 30 has on a first end a tapered edge forming a valve seat of the pressure reducer . this valve seat engages in an opening in the flow path between the inlet port 10 a and the outlet port 10 b . the sleeve 30 is supported on the housing by a shoulder in the region of the opening and is sealed in this region against the housing by a seal 160 . a circumferential shoulder supporting the sleeve in the connecting socket 10 c is formed on a second end of the sleeve 30 opposite the first end , wherein a seal 140 is inserted between the sleeve 30 and the housing 10 in the region of the shoulder . the sleeve has a central third region located between the first region abutting the first end and the second region abutting the second end . the third region has longitudinal slits which extend parallel to the longitudinal axis of the sleeve and are delimited by ribs 30 a connecting the first region and the second region . these longitudinal slits enable fluid to enter the interior of the sleeve 30 from the inlet port 10 a and to exit the sleeve 30 in the direction of the first end , thereby reaching the outlet port 10 b of the housing 10 . a circumferential groove is milled in the region of the housing surrounding the center region of the sleeve 30 , so that the incoming fluid flowing through the inlet port 10 a can flow around the sleeve 30 on all sides and enter the sleeve 30 through the longitudinal slits . the longitudinal slits in sleeve 30 can be covered by a likewise sleeve - like or hollow - cylindrical sieve 40 , which prevents larger particles from passing through the pressure reducer . the inside diameter of the second region of the sleeve 30 is identical to the inside diameter of the sleeve 30 in the region of the valve seat . in this way , a pressure reducer can be realized , which is pressure - equalized under static conditions , i . e ., without flow , and is therefore independent of the upstream pressure and pressure variations on the upstream side , which will be described in more detail below . the sleeve is movably inserted into an arrangement which is composed of a plastic part 20 , a screw 90 , a disk 70 , a sealing disk 110 , and a seal 150 . the parts of this arrangement are rigidly connected with one another . the plastic part 20 extends over almost the entire length of the sleeve 30 . in the first region of the sleeve 30 , the plastic part 20 has wings 20 abutting the inner wall of the sleeve 30 . conversely , on the opposite end of the plastic part 20 , a piston 20 a is formed which sealingly contacts with the interposed seal 150 the inner wall in the second region of the sleeve 30 . the wings 20 c , which extend radially from a hollow - cylindrical section 20 b of the plastic part 20 , are fixedly connected to the piston 20 a by this hollow - cylindrical section 20 b . the plastic part 20 is guided in the sleeve 30 by the piston 20 a and the wings 20 c . the piston 20 a of the plastic part 20 forms an equalization piston whose additional function will now be described in detail . the hollow - cylindrical section 20 b is part of a connecting means , which connects the equalization piston 20 a with the wings 20 c , which form guide means 20 c . the screw 90 , which is screwed into the hollow - cylindrical section and holds the disk 70 and the sealing disk 110 with the plastic part 20 , forms another part of the connecting means . the combination of sealing disk 110 and disk 70 forms a sealing piston 20 , 110 of the pressure reducer . the sealing piston 70 , 110 is fixedly connected with the equalization piston 20 a by the screw 90 and the hollow - cylindrical section 20 b , which forms a connecting means . the diameter of the sealing disk 110 is greater than the diameter of the sleeve 30 in the region of the valve seat , so that flow through the pressure reducer is prevented when the sealing disk 110 — and hence the sealing piston 70 , 110 — contact the valve seat . fig1 illustrates the pressure reducer in this position . however , if the entire arrangement 20 , 90 , 70 , 110 is displaced and the sealing piston 70 , 110 moves away from the valve seat , then the pressure reducer opens , allowing flow from the inlet port 10 a to the outlet port 10 b . the pressure for opening the pressure reducer is typically produced by a compression spring 100 supported on the equalization piston 20 a . the sleeve 30 is inserted into the housing 10 of the pressure reducer and is held in the housing by a cap 60 . the cap 60 has in one section an exterior thread , which is screwed into a corresponding interior thread in the connecting socket 10 c of the housing 10 . the cap 60 has also an interior thread , in which a threaded piece 120 is screwed . the end of the compression spring facing away from the equalization piston 20 a is supported on of this threaded piece 120 . the threaded piece 120 is fixedly connected with a wing nut 50 which extends through a front opening of the cap 60 . the spacing between the threaded piece 120 and the equalization piston 20 a can be changed by a rotating the wing nut 50 , thereby changing the bias force of the compression spring 100 . when the pressure reducer is closed , the sealing disk 110 contacts the valve seat . the free surface of the sealing disk 110 , and hence of the sealing piston 70 , 110 , is subjected to the upstream pressure . the surface of the equalization piston 20 a facing the sealing piston 70 is also subjected to the upstream pressure . due to the identical diameter of the sleeve 30 in the region of the valve seat and in the second region , i . e ., in the region of the equalization piston 20 a , the forces acting on the arrangement consisting of the plastic part 20 , the screw 90 , the disk 70 and the sealing disk 110 produced by the upstream pressure are identical . however , the forces have different , i . e ., opposite directions . the forces therefore cancel each other and the upstream pressure overall does not exert a force on the arrangement 20 , 90 , 70 , 110 . the pressure reducer is therefore independent of the upstream pressure in the closed position . the second exemplary embodiment of the pressure reducer of the invention depicted in fig3 to 6 is different in that the second exemplary embodiment is configured for larger volumes flows and hence has a larger nominal diameter . the connection fittings of valves with a large nominal diameter are typically not implemented as threaded fittings , but as flange fittings , which can be flanged to incoming or connecting pipes . a special fitting for connecting a pressure gauge can be omitted , and replaced by bores disposed in the housing 10 of the second exemplary embodiment , which are either closed with a cover 80 , or into which the pressure gauges 70 are screwed . the housing 10 of the second exemplary embodiment is also implemented as a slanted seat housing , in which the additional components ( valve insert ) of the pressure reducer are inserted . these additional parts are held in the housing 10 by the cap 60 , wherein in this exemplary embodiment the cap 60 is not screwed into the housing , but rather attached to a flange on the housing 10 with screws 180 . a sleeve 30 is first inserted in the housing 10 , wherein the sleeve 30 has the same function as a sleeve 30 in the first exemplary embodiment . a valve seat is formed on the first lower end of the sleeve 30 , wherein the diameter in the region of the valve seat is identical to the diameter of the sleeve 30 on the opposite end , in the region where an equalization piston 190 is movably arranged . whereas in the first exemplary embodiment the pressure equalization piston , a part of the connecting means and the guide means are fabricated from a plastic part 20 , the equalization piston 190 , the connecting means 200 and the guide means 210 in the larger pressure reducer illustrated in fig3 to 6 are assembled from separate parts . the connecting means 200 is formed by a spindle which has an exterior thread on both ends . the exterior threads are , on one hand , screwed into the aforementioned equalization piston and , on the other hand , into a disk 70 which together with a sealing disk 110 forms the sealing piston 17 , 110 of the pressure reducer . the guide means 210 have wings 210 a which are attached to a disk 210 b . this ring 210 b is placed on the end of the spindle 200 facing the sealing piston and clamped to the spindle 200 with the disk 70 . because the sleeve 30 has the same diameter in the region of the valve seat as in the region of the equalization piston 190 , the pressure in the pressure reducer of the second exemplary embodiment is also equalized , i . e ., is in the closed position independent of the upstream pressure or of variations in upstream pressure . in the closed position , only the back pressure operates on the arrangements composed of the sealing cylinder 70 , 110 , the spindle 200 and the equalization piston 190 . if the back pressure increases above the preset value , the pressure reducer closes . conversely , if the back pressure drops below the preset pressure , the compression spring 100 pushes the arrangement composed of the equalization piston 190 , the spindle 200 and the sealing piston 70 , 110 and also the guide means 210 away from the valve seat , thereby opening the pressure reducer . the back pressure , at which the pressure reducer opens or closes , can be adjusted by moving the threaded piece 120 . however , the construction of this threaded piece is different from the threaded piece described above with reference to the first exemplary embodiment . it has a threaded bore , in which a threaded rod 220 is inserted . this threaded rod extends through the front face of the cap and is provided with a head 230 which includes engaging surfaces for engagement with wrenches . by rotating the head 230 and thereby also the threaded rod 220 , the threaded piece 220 is axially displaced , because it is prevented from co - rotating by a headless screw 240 which is guided in a slot 60 a . the headless screw 240 can be used to indicate the preset pressure of the pressure reducer .