turning first to fig1 there is shown a modular dilution station apparatus 10 of the present invention . as depicted , there is a bottle filling unit or frame 12 which is stacked upon a combination bottle / bucket filling unit or frame 14 . both the bottle filling unit 12 and the combination bottle / bucket filling unit are supported on stand 16 . the bottle filling unit 12 and the combination bottle / bucket filling unit 14 each include a plurality of compartments or openings 18 adapted to receive refill modules 20 . each refill module 20 is adapted to hold a quantity of a concentrated chemical to dilute upon dispensing . at the top of each refill module 20 is a venturi housing 22 which is adapted to engage and interface with water supply valve housing 24 . there is a water supply valve housing 24 mounted within each receptacle 18 . each water supply valve housing 24 is manifolded to a single water supply header . located above each compartment 18 is a push button actuator 26 for manually actuating water supply or delivery valves 27 ( see fig1 ). each modular refill 20 includes a dispensing tube 28 which may be inserted into a bottle for filling of the bottle . the combination bottle / bucket filling unit 14 differs from the bottle filling unit 12 in that the base 30 of the combination bottle / bucket filling unit 14 includes a funnelled recess 32 for each compartment 18 . each funnelled recess 32 is slidably or telescopically engaged with base 30 such that it can be slid upward to couple with dispensing tube 28 in a male / female arrangement . extending from each funnelled recess 32 is hose 34 which can be used for filling buckets supported on the floor . the dispensing or distal ends 36 of hoses 34 are supported by brackets extending from base 30 so that hoses 34 are not left to lay on the floor and further to prevent any residual chemicals which may be left in hoses 34 after use from draining onto the floor . shown more clearly in fig3 and 4 is modular refill 20 having venturi housing 22 exploded therefrom . venturi housing 22 shown in detail in fig3 through 7 includes mounting bracket 40 formed integrally therewith . venturi housing 22 is affixed to container 42 by means of mounting bracket 40 which is rectangular in cross section and fits over a rectangular projection 41 extending up from container 42 . mounting bracket 40 includes slots 47 which engage ribs 49 protruding from rectangular projection 41 . venturi housing 22 also includes plate 43 at the top of mounting bracket 40 . co - planar with plate 43 are flanges or wing sections 44 which extend beyond the sides of mounting bracket 40 . flanges 44 extend forward of venturi housing 22 to form handle 46 . extending up from handle 46 are ramps 48 . the rear of venturi housing 22 includes inlet nozzle section 50 . inlet nozzle 50 is cylindrical and is integrally formed with venturi shell 52 . venturi shell 52 is substantially cylindrical with a slight taper . extending forward of venturi shell 52 is outlet or discharge nozzle 54 which is also cylindrical with a slight taper . the cylindrical axes of inlet nozzle 50 , venturi shell 52 and outlet nozzle 54 are substantially colinear . inlet nozzle 50 includes two rectangular ports 56 therethrough . extending downward from plate 43 is circular bracket 58 which is adapted to mate with threaded cap 59 . cap 59 is threadably engaged with spout 60 at the top of container 42 . plate 43 has a plurality of openings or slots 62 therein where plate 43 meets venturi shell 52 and outlet nozzle 54 . the purpose of openings or slots 62 is to prevent venturi shell 52 from being pulled out of round by shrinkage of plate 43 which may occur immediately after manufacture . there is also a vent probe opening 64 through plate 43 . extending substantially vertically upward from plate 43 is guide bar 66 . guide bar 66 is substantially rectangular and is shown partially cut away in fig3 and 4 to expose vent probe 76 and vent probe opening 64 . extending upward from venturi shell 52 is unlocking means or key 68 . mounted over outlet nozzle 54 is vent probe support 70 . vent probe support 70 is substantially semi - cylindrical in configuration and has side brackets 72 extending therefrom . projecting rearward from one of side brackets 72 is flex member 74 . flex member 74 is arcuate and resides between guide bar 66 and venturi shell 56 . extending downward from flex member 74 is vent probe 76 . when vent probe support 70 is mounted over outlet or discharge nozzle 54 , side brackets 72 reside between venturi shell 52 and ridges 78 with vent probe 76 extending down through vent probe opening 64 . vent probe support 70 also includes slot 79 . residing within venturi housing 22 is venturi tube 80 . venturi tube 80 has extending therefrom struts 82 and 83 which are substantially l - shaped . at the distal end of each of struts 82 and 83 there is a protuberance 84 . as venturi tube 80 is inserted into venturi housing 38 , struts 82 flex inwardly due to contact with the internal surface of inlet nozzle 50 . when protuberances 84 are aligned with rectangular ports 56 , struts 82 and 83 spring outwardly causing protuberances 84 to move into and engage rectangular ports 56 thereby fixing the location of venturi tube 80 . when venturi tube 80 is fully inserted , annular extension 86 sealingly engages the internal surface of venturi shell 52 . simultaneously , the discharge or outlet end 88 of venturi tube 80 , which is slightly tapered , sealingly engages the internal surface of outlet or discharge nozzle 54 . preferably , the degree of taper of the internal surface of outlet nozzle 54 differs from the degree of taper of the discharge end 88 of venturi tube 80 . this difference in degree of taper will promote a wedged coupling of venturi tube 80 to outlet nozzle 54 enhancing the sealed relationship without the need for gaskets . venturi tube 80 includes a restriction throat 90 across which a pressure drop is generated during operation . downstream of the restriction throat 90 is orifice 92 . during operation , the pressure drop taken across restriction throat 90 causes the chemical concentrate in container 42 to be drawn through orifice 92 . orifice 92 must therefore be sized for the specific chemical concentrate being diluted to ensure that the water / chemical mixing ratio is correct . the inlet end 94 of the venturi tube 80 includes an annular recess of 96 which provides a residence for an 0 - ring 98 . when a refill module 20 is fully inserted into a compartment 18 , the water supply nipple extending from water supply valve 27 will have been inserted into inlet nozzle 50 and about inlet end 94 with 0 - ring 98 providing a seal for the male / female coupling of the water supply nipple to inlet end 94 . the use of struts 82 to affix venturi tube 80 within venturi housing 22 provides a significant advantage . venturi housings 22 will be identical regardless of what concentrate is contained in refill module 20 . only the proper venturi tube 80 need be selected and the only difference between venturi tubes 80 is the size of orifice 92 . struts 82 and 83 are unequal in size so that venturi tube 80 can be installed in only one orientation . the protuberance 84 of strut 82 which fits under the rectangular port 56 at the top of housing 22 is coded during manufacture to identify the diameter of that particular orifice 92 . the code on protuberance 84 allows inspection of the assembled refill to assure the proper orifice 92 and , hence , the proper dilution of the cleaning concentrate . extending downward from venturi shell 52 is cylindrical skirt 100 which sealingly engages draw tube nozzle 101 integrally formed with threaded cap 59 . press - fit into draw tube nozzle 101 and extending downward therefrom into container 42 is draw tube 102 . mounted to the base of draw tube 102 is foot 103 which is intended to rest on the bottom wall of container 42 . foot 103 includes a series of indentations 105 in the bottom edge thereof such that chemical concentrate can flow through indentations 105 . mounted within foot 103 is filter screen 111 to ensure that any particulates which may accidentally be held within contain 42 cannot flow through draw tube 102 and potentially foul orifice 92 . mounted to outlet nozzle 54 is dispensing tube 28 . dispensing tube 28 includes a ribbed portion for added strength and flexibility . as best seen in fig2 , the cross section of dispensing tube 28 is substantially circular with a flat surface 104 on one side thereof which extends for substantially the length of dispensing tube 28 . a portion of dispensing tube 28 may be sandwiched between outlet nozzle 54 and vent probe support 70 to aid in the retention of dispensing tube 28 on outlet nozzle 54 . also to aid retention of dispensing tube 28 on outlet nozzle 54 , one of the ribs of dispensing tube 28 may project through slot 79 . dispensing tube 28 includes a flat surface 104 which is located on that side of the dispensing tube 28 nearest container 52 and furthest away from a person operating the dilution station 10 . flat surface 104 is an important safety feature and preferably includes spine 113 projecting perpendicularly therefrom . when an operator inserts dispensing tube 28 into a bottle for filling , the flat surface 104 ensures that there will be a vent gap between the flat surface 104 and the neck of the bottle being filled . further , because the flat surface 104 is located on the side of the dispensing tube away from the operator , should the operator overfill a bottle , back splash and overflow will be directed back toward the dilution station 10 and away from the operator . spine 113 insures that when dispensing tube 28 is inserted into a bottle , flat surface 104 is separated from the neck of the bottle maintaining the vent gap away from the operator . looking next at fig1 through 18 there is shown in detail the water supply valve assembly 24 of the present invention . water supply valve assembly 24 includes push button actuator 26 which has connected thereto rod 106 . push button actuator 26 includes a piston 108 formed integrally therewith which resides in cylinder 110 . push button actuator 26 also includes an annular lip 112 at the distal end thereof . there is a travel stop lip 114 radially extending from piston 108 . travel stop lip 114 serves as a travel stop preventing push button 26 from being fully inserted into cylinder 110 . annular lip 112 serves as a means for pulling out push button 26 should it become jammed for any reason in cylinder 110 . cylinder 110 is formed integrally with frame 116 . the distal end of rod 106 extends to and through magnet bracket 118 which is slidably supported upon valve frame or housing 116 . extending upward from valve frame or housing 116 intermediate to magnet bracket 118 and cylinder 110 is retainer 120 . retainer 120 includes a u - shaped slot 122 at the top thereof through which rod 106 extends . residing about rod 106 and located between cylinder 110 and retainer 120 is spring 124 . a washer 121 is provided on rod 106 adjacent retainer 120 . rearward of retainer 120 are guide rail supports 126 which extend upward from frame 116 and are substantially parallel to rod 106 . extending from magnet bracket 118 and formed integrally therewith are skids 128 . formed integrally with frame 116 and guide rail supports 126 are lower guide rails or tracks 127 which are substantially u - shaped in cross section . extending from legs 126 are a first pair of upper guide rails 129 and extending from retainer 120 are a second pair of upper guide rails 133 . skids 128 slide horizontally in tracks 127 and upper guide rails 129 and 133 . there is a washer 130 retained at a position on rod 106 by snap ring 131 and a spring 132 . spring 132 resides about rod 106 between washer 130 and magnet bracket 118 . affixed to magnet bracket 118 is magnet 134 . skids 128 have notches 136 therein . locking bar 138 resides in and across notches 136 . locking bar 138 is affixed to pivot bar 140 which is pivotally connected to ears 139 extending up from frame 116 . ears 139 include journals 145 in which pin 147 resides . there is a spring 141 residing across the top of pivot bar 140 and extending down through a slot 143 and into a bore in pivot bar 140 . spring 141 urges pivot bar 140 and locking bar 138 downward such that locking bar is forced into notches 136 . the distal end of rod 106 includes a widened section 142 which has a radius larger than the radius of bore 144 in magnet bracket 118 . a pin through or a cap on rod 106 or other spring retaining means may be substituted for widened section 142 . forward of magnet bracket 118 there is affixed to housing or frame 116 water supply valve 27 which is a solenoid valve with stem 146 extending vertically therefrom . note that the coil has been removed from stem 146 and solenoid valve 27 is open and closed by moving magnet 134 into and out of close proximity with stem 146 . in such manner , solenoid valve 27 is operated without connection to an external electrical power source . extending down from pivot bar 140 is lever 148 which extends into slot 150 in frame 116 . when an upward force is directed onto lever 148 , pivot bar 140 will rotate upward lifting locking bar 148 from notches 136 thereby allowing lateral movement of skids 128 and magnet bracket 118 . extending downward from plate 152 of valve housing 116 are guide members 154 . ( see fig1 .) each guide member 154 includes a series of gussets 155 which stiffen and add strength to guide members 154 . between each pair of gussets 155 there extends a ledge 156 projecting from the inner face of guide members 154 . when a disposable container 20 is inserted into a receptacle 18 , guide members 154 serve to direct mounting bracket 40 therebetween such that flanges 44 reside on or above ledges 156 . the lead portion of ledges 156 are downward for easier insertion of container 20 . when disposable container 20 is fully and properly inserted into a receptacle 18 such that inlet nozzle 50 sealingly engages water supply line 158 , key 68 will have moved to a position to engage lever 148 driving it upward thereby rotating pivot bar 140 upward and releasing locking bar 138 from notches 136 . thus , when push button actuator 26 is pressed inward , spring 124 is compressed and the force is transmitted through rod 106 and spring 132 to thereby move magnet 134 and magnet bracket 118 into close proximity with solenoid valve 146 . as push button actuator 26 is released spring 124 drives rod 106 , magnet 134 and magnet bracket 118 to their original position and spring 141 urges pivot bar 140 to rotate downward such that locking bar 138 reoccupies notches 136 . if a disposable container 20 has not been fully and properly inserted into receptacle 18 such that inlet nozzle 50 has failed to sealingly couple with water valve 27 key 68 will not have engaged lever 148 . locking bar 138 will still reside in notches 136 and pressure on push button actuator 26 will result in the compression of springs 124 and 13 while locking bar 138 holds magnet and magnet bracket 118 in their original positions . when a refill module 20 is inserted into a compartment 18 . handle 46 must be deflected slightly downward to allow ramps 48 to pass by arms 166 . once ramps 48 move past arms 166 , handle 46 springs upward such that ramps 48 engage the back side of arms 166 thereby locking refill module 20 in place . ( see fig2 .) in order to remove a refill module 20 from a compartment 18 , handle 46 must be depressed and pulled simultaneously to allow ramps 48 to get past arms 166 . ridges 48 thus lock a refill module 20 within a compartment 18 and ensure that water pressure through venturi housing 22 will not cause venturi housing 20 to separate from water valve supply housing 24 breaking the sealed engagement therebetween . to prevent refill module 20 from leaking during shipping , refill module 20 is sent with shipping plug 162 inserted through dispensing tube 28 and venturi tube 80 . shipping plug 162 includes a series of annular projections 164 extending therefrom which engage the internal walls of venturi 80 downstream of orifice 92 and diameter which presses sealingly into throat 90 . shipping plug 162 contains any chemical concentrates which may flow from container 42 through draw tube 102 , draw tube nozzle 100 and orifice 92 into venturi tube 80 during shipping thus preventing chemical concentrates from spilling out of refill module 20 . because container 42 is substantially rigid and will not collapse as concentrate is taken therefrom , a vent hole must be provided through threaded cap 59 the plastic or foil seal over spout 60 . failure to provide a vent hole would result in the attempt to pull a vacuum on container 42 when operating the venturi arrangement of the present invention . this vent hole is provided automatically upon insertion of the refill module 20 into a receptacle 18 . extending down from plate 152 are plate members 166 . as mounting bracket 40 is moved into position such that flanges 44 slide in above ledges 156 and between guide members 154 , one of the plate members 166 passes between venturi shell 52 and guide bar 66 thereby engaging and depressing flex member 74 . the downward movement of flex member 74 drives vent probe 76 downward into and through recess 168 in threaded cap 59 . recess 168 is actually a thin area of limited structural integrity in cap 59 and intrusion by vent probe 76 punctures or ruptures that thin area . as refill module 20 is fully inserted into compartment 18 , flex member 74 moves along arm 166 and reaches recess 167 which allows flex member 74 to resume its original shape thereby retracting vent probe 76 from the hole just created in the seal over spout 60 . it can thus be seen that flex member 74 is , essentially , a leaf spring . each plate member 166 includes a notch 169 . as a refill module 20 is properly inserted into a compartment 18 ramps 48 contact plate members 166 causing handle to depress . when the refill module 20 is fully inserted , handle 46 springs upward with ramps 48 residing in notches 169 thereby locking refill module 20 within compartment 18 . in order to remove refill module 20 from compartment 18 , handle must be depressed far enough so that ramps 48 no longer reside within notches 169 . there are a series of rectangular ports 170 through plate 152 of frame 116 . ports 170 perform no function in the operation of water supply valve assembly 24 . ports 170 are necessary to mold frame 116 , retainer 120 , guide rail supports 126 , tracks 127 , upper guide rails 129 and 133 , guide members 154 , gussets 155 , ledges 156 and plate members 166 into a single , integrally formed piece . in operation , upon proper insertion of a refill module 20 into a compartment 18 , solenoid valve 27 may be actuated by operation of push button actuator 26 . in such manner , water is caused to flow through venturi tube 80 . the resultant pressure drop taken across restriction throat 90 draws chemical concentrate from container 42 , through indentation 105 , foot 103 , draw tube 102 , port 171 in draw tube nozzle 101 , cylindrical skirt 100 , bore 172 in venturi shell 52 and orifice 92 to intermix in a predetermined ratio with the water flowing through venturi tube 80 . as stated earlier herein , the predetermined ratio is set by the water pressure within venturi tube and the diameter of orifice 92 . it should be recognized that the bottle filling unit 12 can be used with or without the combination bottle / bucket filling unit 14 , or vice versa . further , both the bottle filling unit 12 and the combination bottle / bucket filling unit 14 can be sized to have one or more compartments 18 . thus , a bottle filling unit 12 may be downsized from that depicted in the drawings such that it has a single compartment 18 for receipt of a single deposable container 20 . it should further be recognized that in order to perform precision dilution of chemical concentrates with a venturi , the water supply pressure must be known and it must be consistent . with the installation of each dilution station 10 of the present invention , it will therefore be necessary to measure the pressure of the water supply header , and , perhaps , install a pressure regulating device on the line from the water supply header to the dilution station . from the foregoing , it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are apparent and which are inherent to the apparatus . it will be understood that certain features and subcombinations are of utility and may be employed with reference to other features and subcombinations . this is contemplated by and is within the scope of the claims . as many possible embodiments may be made of the invention without departing from the scope thereof , it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense .