inlet passage 12 and an upper outlet passage 13 an elongated valve cartridge 14 is removably mounted within the opening 11 being held therein by a split ring retainer 15 which is disposed within a recess formed adjacent to the outer end of the opening 11 a washer 16 is disposed between the retainer 15 and the adjacent portion of the body 10 the outer end of the opening 11 is provided with internal screw threading 17 which engages external screw threading 18 formed on the outer portion of the cartridge 14 an on off control knob 19 is fixedly secured to the outer end of the cartridge 14 rotation of the knob 19 causes rotation of the cartridge 14 to move it longitudinally toward or away from the inner end of the opening 11 the valve cartridge 14 is provided with a tapered inner end 20 having an inlet 21 within which is mounted a sintered metal filter 21a the inlet 21 is connected to a passage 22 which extends along the longitudinal axis of the cartridge 14 to a chamber 23 which is in turn connected to a transversely directed outlet 24 the outlet 24 is in turn connected to a movable chamber 25 which surrounds the cartridge 14 and which is connected with the outlet passage 13 of the body 10 the chamber 25 is defined longitudinally by a pair of outwardly projecting rings 26 and 27.