between the fluid passage 40 and the exhaust flow passage 42 may alternatively be provided an axially extending generally tubular inner sleeve 52 is axially slidingly and sealingly received within a lower portion 54 of the valve housing 34 the inner sleeve 52 is substantially radially outwardly surrounded by an axially extending generally tubular mandrel 56 the mandrel 56 is threadedly and sealingly attached to the upper centralizer housing 22 the fluid passage 40 extends radially between the inner sleeve 52 and the mandrel 56 referring specifically now to fig1 c an opening 58 is formed radially through the mandrel 56 the fluid passage 40 extending through the opening an axially extending generally tubular coupling 60 is axially slidingly and sealingly disposed exteriorly on the mandrel 56 such that the opening 58 is axially between circumferential seals 62 carried internally on the coupling an opening 64 is formed radially through the coupling 60 thereby permitting fluid communication between the opening 58 and a generally tubular screen member 66 exteriorly disposed on the coupling the screen member 66 includes a perforated inner tube 68 thus it may be seen that the fluid passage 40 is in fluid communication with the annulus 44 and that the fluid passage permits fluid flow from the annulus 44 to the valve housing 34 when the fluid pump is operated as more fully described hereinbelow fluid from the annulus 44 is forced into.