Patent Publication Number: US-2009236277-A1

Title: Modular Drinking Water Filtration System with Internal Sealing Between Valve Spindle and Head

Description:
BACKGROUND OF THE INVENTION 
     The present invention pertains to a drinking water purification system and, more particularly, to a modular system for under-counter or under-sink installation using replaceable cartridges and which may be configured in a system utilizing up to four cartridges, including a reverse osmosis (RO) cartridge. 
     A drinking water filter system adapted for under-counter mounting is shown in U.S. Pat. No. 6,436,282. The system is disclosed with three replaceable filter cartridges, one of which is an RO filter cartridge. The three cartridges are connected to a common header, but the dissimilarity between the three cartridges may require the use of a different attachment head within the header for each filter cartridge. Also, the header is designed for three cartridges, whereas it would be desirable to have a modular system utilizing from one to four filter cartridges, depending on the particular application. 
     It would also be desirable to have a modular system that could utilize from one to four separate filter cartridges, one of which could be an RO cartridge, in which the system could be assembled by the manufacturer or seller using identical filter heads and modularly connected mounting devices. Most cartridges could be provided with mounting arrangements and flow connections using the same head with the heads serially interconnected to form the desired configuration. An RO cartridge requiring a non-standard head could be designed for use in the modular assembly. It would also be desirable to have a modular system in which a proprietary fit could be provided that matches the filter cartridge to the head to assure proper fit. 
     The modular system described above, lends itself to an under-sink or under-counter system that is easy to install and provides easy cartridge replacement. Applying this modular design to the system of the present invention also provides the ability to utilize common filter heads with identical internal flow valve spindles that are controlled by attachment and removal of the filter cartridge, a simple and effective way of providing a seal between the spindle and the head, customizable key arrangement between the filter cartridge and the head that can be utilized to provide a proprietary feature for a seller and to assure use of the proper replacement cartridge, the ability to easily remove and replace the RO control valve in a special RO cartridge and head, and special assembly techniques that facilitate assembly of filter cartridges, including axially aligned inlet and outlet, color coded end rings and high friction end caps for facilitating cartridge replacement. 
     SUMMARY OF THE INVENTION 
     The present invention, in its various aspects, is applied to the combination of a replaceable water filter cartridge that has a filter body with an axially extending neck on one end, the neck having an inlet and an outlet for water, and a filter head that has an outer housing defining a cylindrical interior wall with an inlet opening for water to be treated and an outlet opening for treated water. A valve spindle is disposed in the outer housing for reciprocal rotary movement on the filter body axis between flow and no-flow positions, whereby connection and disconnection of the outer housing inlet opening and outlet opening with the cartridge inlet and outlet are provided. The spindle has an interior chamber for receipt of the cartridge neck to provide the flow connection and disconnection. 
     In accordance with one aspect of the present invention, an improved flow path and seal arrangement is provided whereby the spindle has a cylindrical outer wall portion that is positioned in closely spaced coaxial relation to the cylindrical interior wall of the outer housing; a pair of diametrically opposed and coaxially aligned flow ports are provided in the spindle outer wall portion which are aligned with the outer housing inlet and outlet openings in the flow position and out of alignment with those openings in the no-flow position; a unitary dual function seal is provided for each flow port, with each seal supported on the spindle outer wall portion and having an inner peripheral sealing rib that surrounds the flow port in the flow position and is in sealing engagement with the cylindrical interior wall of the outer housing in both the flow and no-flow positions, and an outer peripheral sealing rib surrounding the inner sealing rib and constructed and positioned to be in sealing engagement with the interior wall of the outer housing in both the flow and no-flow positions, the inner and outer ribs together preventing flow in the no-flow position. 
     The improved flow path and seal arrangement preferably includes a mounting recess in the face of the spindle outer wall portion in which the inner and outer sealing ribs of the seal are received. An intermediate web connects the inner and outer sealing ribs and is seated in the mounting recess. The inner rib is preferably circular in shape, and the mounting recess is provided with an integral cylindrical nipple that defines the flow port and extends radially outward into sealing and supporting contact with the seal inner rib. 
     In accordance with another aspect of the invention, an arrangement is provided to assure compatibility and operative connection of the cartridge to the filter head. The arrangement includes a first adaptor ring that has a first half of a locator device formed thereon, the first adaptor ring is mounted in the head coaxially with the interior wall with the first half of the locator device positioned at a circumferentially selected position. A second adaptor ring has a second half of the locator device formed thereon, the second adaptor ring is mounted on the filter cartridge surrounding the neck and coaxially therewith. The second half of the locator device is positioned at a circumferentially selected position to engage the first half and to permit operative connection of the cartridge to the head. 
     In a presently preferred embodiment, the upper adaptor ring and the lower adaptor ring are provided with integral weld flanges that seat in respective complementary weld grooves in the spindle and on the neck of the cartridge body. The rings are secured by spin welding. The exposed face of the upper adaptor ring have a pair of diametrically opposite axial extending fingers that engage a pair of diametrically opposite recesses in the lower adaptor ring to ensure compatibility between the filter cartridge and the head. The upper and lower adaptor rings may be selectively circumferentially repositioned to provide a proprietary fit for selected customers. Further, the position of the fingers and complementary recesses may be varied radially on the ring surfaces to provide an even broader range of proprietary fits. 
     In another embodiment, the first half of the locator device comprises a first axially facing non-planar surface that defines a first axially extending abutment face. The second half of the locator device comprises a second axially facing non-planar surface that complements the first non-planar surface and defines an oppositely facing second axially extending abutment face. Relative rotation and axial displacement of the cartridge on its axis and with respect to the filter head interior wall results in engagement of the abutment faces. It is particularly preferred to use diametrically opposed pairs of first and second halves of the locator device. 
     One of the axially facing non-planar surfaces has an axial protrusion that defines the abutment face, and the other axially facing non-planar surface has an axial recess that defines the abutment face. Preferably, the filter head comprises an outer housing that defines an inner cylindrical wall having an inlet opening for water to be treated and an outlet opening for treated water. A valve spindle is rotatably disposed in the outer housing for rotary reciprocal movement between flow and no-flow positions that connect and disconnect the outer housing inlet opening and outlet opening with the cartridge inlet and outlet, respectively. The valve spindle defines the cylindrical interior wall for receipt of the cartridge neck. 
     The first adaptor ring is attached to a first mounting surface on the cylindrical interior wall of the valve spindle, and the second adaptor ring is attached to a second mounting surface on the neck of the filter body. The first and second mounting surfaces comprise annular shoulders of generally the same diameter. The adaptor rings are preferably attached to their respective mounting surfaces with welds, preferably friction welds, and more preferably spin welds. The adaptor rings are positioned circumferentially to assure engagement of the second abutment face of a selected filter cartridge with the first abutment face in the spindle. 
     In a variant embodiment, the first half of the locator device comprises a notch formed in the first adaptor ring, and the second half of the locator device comprises an axially extending finger on the second adaptor ring, the finger sized and positioned to engage the notch to establish operative connection. A housing is provided for the filter body that has a circular open end through which the neck of the filter body extends. An annular end cap interconnects the filter body and the neck and provides a sealed connection to the open end of the housing in a fully assembled state. An orientation recess is provided in the end cap to engage with a complementary orientation tab on the inside of the housing open end. The tab is received in the recess in the fully assembled state to fix the circumferentially selected position of the finger on the second adaptor ring. The adaptor rings in this embodiment are attached with welds, preferably ultrasonic welds. 
     In accordance with another aspect of the present invention, an arrangement is provided for mounting the filter head and demountably supporting the filter cartridge, the arrangement includes a mounting bracket and an integral mounting ring. The improved arrangement includes a filter head outer housing with a pair of oppositely extending coaxial sleeves that define the inlet opening and the outlet opening. A mounting lug arrangement is provided on the filter head outer housing and a cooperating slot arrangement is provided on the mounting ring to permit the housing and valve spindle to be connected and locked to the mounting ring in an operative position. The outer housing has a lower cylindrical skirt and the lug arrangement includes a pair of diametrically opposite mounting lugs that are integrally formed on the lower edge of the skirt. The mounting ring has an annular recess for receipt of the housing cylindrical skirt and a pair of slots for receipt of the mounting lugs, one of the mounting lugs adapted to fit in only one of the slots to assure proper flow orientation of the co-axial inlet and outlet sleeves. A circular track in the mounting ring annular recess is dimensioned to receive the mounting lugs in response to rotation of the outer housing in the recess, and a stop detent on the cylindrical skirt overrides and engages a first stop in the track to prevent reverse rotation and establish the operative position. In addition, a locking detent is provided on the cylindrical skirt to engage a second stop in the track, the second stop preventing reverse rotation of the outer housing from the operative position. 
     The apparatus also includes an arrangement for operatively attaching the filter cartridge to the mounting ring and the filter head. In this arrangement, a pair of opposed attachment lugs are provided on the neck of the filter cartridge, a pair of entrance slots are provided in the lower edge of the mounting ring for receipt of the attachment lugs upon vertical upward axial movement of the cartridge neck into the filter head. The entrance slots terminate in an annular shoulder that is engageable by and supports the attachment lugs in response to rotational movement of the attachment lugs along the shoulder relative to the mounting rings. The filter cartridge is thereby supported in an operative position by the mounting ring. Preferably, the lead ends of the attachment lugs, in the rotational direction, are provided with tapered faces and the entrance slots are provided with cooperating ramped faces to facilitate axial and rotational movement of the cartridge. 
     Preferably, the lower end of the valve spindle is provided with a spindle skirt in the lower edge of which is provided a pair of notches. Cooperating semi-annular recesses are formed in the inner lower edge of the outer housing skirt to receive the attachment lugs. The notches have end faces that are engageable by the lead ends of the attachment lugs in response to rotational movement of the lugs to establish a rotational limit of the filter cartridge and the operational position thereof. 
     In a related embodiment, the mounting bracket is preferably rectangular in shape, and the mounting arrangement includes a modular back plate that has a generally planar base and a front mounting face having an open-ended mounting slot defined by parallel tracks. The mounting slot is adapted to receive the edges of the mounting bracket as it is inserted into the open-ended slot, and a bracket stop is engageable by the mounting bracket upon full insertion thereof into the slot. Preferably, the bracket stop comprises a notch in one edge of the mounting bracket engageable by a detent in the associated track. The back plates are preferably provided with parallel opposite edges that have complimentary engagement devices for modular interlocking connection of adjacent back plates. 
     The face of the back plate extends away from the mounting slot and includes a reinforcing guide arrangement adapted to engage and facilitate axial alignment of the filter cartridge body for attachment to the mounting ring, and to stiffen the mounting bracket. Preferably, the reinforcing guide arrangement comprises a pair of spacer panels extending perpendicularly from the mounting face and a series of spaced gussets connected to the mounting face, the panels support a cradle between the panels for supporting the filter cartridge body. 
     The mounting arrangement also includes a cover that has a hinged connection to the back plate along one edge adjacent the filter head. The opposite edge of the cover has a latching connection to the other edge of the back plate. The cover encloses the filter head and the mounting ring and has passages that are axially aligned, in the latched position, with the mounting ring. This arrangement allows the filter cartridge to be removable and replaceable through the passages in the cover by manual engagement of the free end of the cartridge. The side edges of the cover preferably include complementary connecting devices to provide modular interlocking of adjacent covers. 
     In accordance with another aspect of the present invention, an arrangement is provided for the removal and replacement of a special spindle for use with a reverse osmosis or other semi-permeable membrane filter cartridge. The valve spindle for use with an RO cartridge houses a special dual diaphragm shut off valve that is replaceable with the spindle. In this embodiment, the spindle is demountably locked to the filter head outer housing. A spindle lock arrangement includes an annular groove in an exterior wall of the spindle, preferably above the dual function seals. The exterior spindle wall is coaxial with the spindle outer wall portion and the groove is provided with a slot that forms an axially extending passage therethrough. A lug on the interior of the filter head outer housing is received in the groove and holds the spindle against axial displacement from the filter head housing over a range of spindle rotation including spindle movement between the flow and no-flow positions. The lug is adapted to move circumferentially in and relative to the annular groove and axially relative to and through the slot in response to disconnection of the filter cartridge, manual rotation of the spindle beyond the above identified range, and axial movement of the spindle out of the outer housing. 
     The filter cartridge comprises a semi-permeable membrane filter. The semi-permeable membrane may comprise an ultra filter membrane or a reverse osmosis membrane. 
     The mounting ring for the filter head and cartridge includes an annular recess for receipt in one axial direction and attachment of the filter head housing, and for receipt in the opposite axial direction and demountable attachment of the filter cartridge neck. The filter housing and cartridge neck capture the spindle in an operative position therebetween. The apparatus is preferably provided with a manually operable removal tool that has a spindle engagement lug on one axial end that is adapted to engage the spindle to overcome seal friction and facilitate spindle removal. 
     The water filter elements used in the apparatus of the present invention are carried in housings of similar size and shape to accommodate modular construction in addition to convenient replaceability. A preferred method for assembling a water filter element in a housing for such a replaceable filter cartridge utilizes a housing that has an open operative end defined by an annular reduced diameter portion. The filter element has an end closure with an axially extending neck that sealingly engages the interior of the reduced diameter portion of the housing and includes an end that extends axially past the reduced diameter portion. The engagement of the filter element with the interior of the reduced diameter portion of the housing defines a stop position. The neck also has an inlet and an outlet for water. The assembly method includes the steps of (1) providing the opposite end of the housing with an annular opening for receipt of the filter element, (2) inserting the filter element axially through the annular opening until the element reaches the stop position, (3) attaching a retaining ring to the neck of the filter element at a position axially beyond and in engagement with the end of the reduced diameter portion of the housing when the filter element is in the stop position to retain the element from reverse axial movement, and (4) attaching a housing end cap to the annular opening in the housing to seal the opening and to hold the filter element in the stop position. 
     The foregoing method preferably includes the steps of (1) providing an annular groove in the neck of the filter element, and (2) placing the retaining ring in the annular groove. The retaining ring preferably comprises an O-ring. 
     The method also preferably includes attaching the housing end cap by spin welding. Ultrasonic welding may also be used. It is also preferred to attach a cap grip to the housing end cap which cap grip may include the step of coding the cap grip with cartridge identification indicia. Such indicia may comprise color coding. The attaching step may comprise snap fitting and the grip preferably is provided with a high friction surface to enhance manual gripping. 
     A subassembly provided by the foregoing assembly method includes a cylindrical housing that has an opening having an open operative end defined by an annular reduced diameter portion and an annular opening in the opposite end of a diameter larger than the diameter of the open operative end. A filter element is positioned in the housing and has an end closure with an axially extending neck making sealing contact with the interior of the reduced diameter portion. The filter element has a major diameter smaller than the annular opening and larger than the open operative end such that the filter element is positioned in the housing against an axial stop to define an operative position. A retaining ring is attached to the filter element neck at a position axially beyond and in engagement with the end of the reduced diameter portion of the housing to retain the element against axial movement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a drinking water filtration system utilizing the modular construction of the present invention. 
         FIG. 2  is a side elevation view of the system shown in  FIG. 1 . 
         FIG. 3  is perspective view of the filter system with the enclosing housing opened to show features of the system construction. 
         FIG. 4  is an exploded perspective view of the mounting bracket and filter head subassembly. 
         FIG. 5  is a perspective view of the subassembly shown in  FIG. 4  with the filter head attached to the mounting bracket. 
         FIG. 6  is a vertical section of the subassembly shown in  FIG. 5 , additionally showing the valve spindle. 
         FIG. 7  is horizontal section taken on line  7 - 7  of  FIG. 5 . 
         FIG. 8A  is an exploded elevation view of the filter head, mounting racket and filter cartridge assembly. 
         FIG. 8B  is an exploded vertical section of the head, mounting bracket and filter cartridge assembly taken on line  8 B- 8 B of GI.  8 A. 
         FIG. 9  is a perspective view of the valve spindle shown in  FIGS. 6 and 8 . 
         FIG. 10  is a perspective view similar to  FIG. 9  and additionally showing the dual function seal. 
         FIGS. 11 and 12  are perspective views of complementary adaptor rings for use in the filter assembly of  FIG. 8   
         FIGS. 11A and 12A  are perspective views of an alternate embodiment of the adaptor rings shown in  FIG. 8 . 
         FIG. 13  is a vertical section through an embodiment of the filter system utilizing a reverse osmosis filter cartridge. 
         FIG. 14  is an enlarged sectional detail of  FIG. 13 . 
         FIGS. 15A ,  15 B and  15 C are enlarged sectional details, similar to  FIG. 14 , but taken on different rotational vertical planes to show additional elements of the system construction. 
         FIG. 16  is a top plan view of the mounting bracket and mounting ring for the system shown in  FIG. 13 . 
         FIG. 17  is a bottom perspective view of the RO filter head used in the  FIG. 14  detail. 
         FIG. 18  is a perspective view of the RO filter cartridge used in the  FIG. 13  system. 
         FIG. 19  is a perspective view of the cartridge shown in  FIG. 18  attached to the mounting ring and filter head. 
         FIG. 20  is a perspective view of the valve spindle shown in  FIGS. 14 ,  15 A and  15 B. 
         FIG. 21  is an enlarged perspective view of the spindle drive ring shown in  FIGS. 14 ,  15 A and  15 B. 
         FIG. 22  is an elevation view of the RO filter element. 
         FIG. 23  is a perspective view of the end cap for the filter element shown in  FIG. 22 . 
         FIG. 24  is a perspective view of the adaptor ring for the filter element shown in  FIG. 22 . 
         FIG. 25  is a perspective view of the adaptor ring for the spindle shown in  FIG. 20 . 
         FIG. 26  is a bottom plan view of the spindle shown in  FIG. 20 . 
         FIG. 27  is a perspective view of a spindle removal tool. 
         FIG. 28  is a perspective view of a filter element of the cartridge shown in  FIG. 8 . 
         FIG. 29  is a perspective view of the housing for the element shown in  FIG. 28 . 
         FIG. 30  is a partially exploded view of the assembly of the filter element in  FIG. 28  and housing in  FIG. 29 . 
         FIG. 31  is a vertical sectional view of another arrangement for assuring filter compatibility and operative connection. 
         FIG. 32  is an enlarged view of a portion of  FIG. 31  showing the unlocking of the spindle from the head. 
         FIG. 33  is a top plan view of the adaptor ring used in the  FIG. 31  arrangement. 
         FIG. 34  is a view similar to  FIG. 32  showing the fully unlocked position. 
         FIG. 35  is a perspective end view of the valve spindle and locking pin arrangement. 
         FIG. 36  is a perspective bottom view of the adaptor ring shown in  FIG. 33 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The water filter system  10  shown in  FIG. 1  includes three replaceable filter cartridges that are hydraulically connected to provide serial treatment of untreated water entering the system via inlet  12  and exiting the system as treated water via outlet  13 . Each cartridge  11  forms part of an independent filter module  14  that can function as a separate filter unit or, as shown, be connected to adjacent modules  14  to form a system including as many as four or more cartridge modules. Furthermore, the cartridges  11  chosen for use in the modular system  10  can perform widely varying filter functions. For example, in the system shown, the first cartridge directly receiving untreated water through the inlet  12  may comprise a granular activated carbon filter element. The second cartridge, receiving pretreated water from the first cartridge may comprise a reverse osmosis (RO) filter unit, and the third cartridge  17  may comprise a final or polishing filter that receives filtered water directly from the RO filter  16  (or from a pressurized storage tank, not shown) from which it is discharged for use via the treated water outlet  13 . 
     The filter system  10  shown in  FIG. 1  is mounted with the filter cartridges  11  disposed vertically on their axes, but an important feature of the present invention permits the attachment of a modularly constructed system at virtually any orientation of the cartridges. Furthermore, as will be explained in greater detail, the modular filter system  10  lends itself well to custom assembly of the system to meet a customer&#39;s particular needs in a manner utilizing common parts and convenient interconnection. 
     Each filter module  14  includes a back plate  18  that comprises the main support structure and provides the means for mounting the module to any convenient flat surface, such as the inside surface of a cupboard below a sink. The back plate  18  has a generally planar base  20  that includes a pair of spaced universal mounting openings  21  for convenient attachment of the back plate to the supporting surface. The front face of the back plate  18  has an open-ended mounting slot  22  defined by a pair of parallel tracks  23 . The mounting slot tracks  23  are sized to receive the edges of a rectangular mounting bracket  24  that carries an integral mounting ring  25 . The mounting ring  25  provides support for and an interconnection of a cartridge  11  and a filter head  26 , which interconnection will be described in greater detail below. 
     The mounting bracket  24 , carrying the mounting ring  25 , is slid into the tracks  23  defining the mounting slot  22  until an internal bracket stop is engaged when the mounting bracket is fully inserted. The bracket stop may comprise a notch  27  in one edge of the bracket that is engaged by a detent  28  in the associated track  23  when the bracket is fully inserted. Because the mounting slot  22  is open ended on both ends, the mounting bracket  24  may be slid directly through the mounting slot  22  on one back plate  18  and into the mounting slot on the next adjacent back plate by manually overcoming the locking provided by the bracket stop  29  and moving the mounting bracket linearly. 
     The side edges  30  of the back plates  18  are provided with complementary hook-and-slot edge connectors  31 , enabling adjacent back plates to be interconnected to provide a modular construction. A portion of the back plate base  20  provided with a reinforcing and cartridge guide arrangement  32  that includes a pair of spacer panels  33  that include stiffening gussets  34  and between which is supported a cradle  35  that helps support and guide the cartridge  11  as it is inserted through the mounting ring  25  and into operative engagement with the filter head  26 . Certain of the stiffening gussets  34  are also provided with hook-and-slot edge connectors  36  to help provide rigidity in the modular assembly of back plates  18 . 
     Adjacent filter heads  26  are interconnected with flexible tubular connectors  39 . A connector  39  has one end inserted in an inlet sleeve  48  in the filter head and the other end in an outlet sleeve  50  of the next adjacent filter head. Axial alignment of the inlet and outlet sleeves  48  and  50  makes connection of adjacent filter modules  14  easy and reliable. 
     The modular assembly of the filter system  10  is completed with an enclosing housing  37  that further helps secure the filter cartridges  11  in their mounted positions, facilitates cartridge removal and replacement and provides an aesthetic covering for the system. The housing is also modular insofar as each back plate  18  carries its own housing module  38 . Each housing module has a hinged connection  40  to an edge of the back plate  18 , enabling the housing module  38  to be pivoted away from the back plate for installation of the mounting bracket  24  and filter head  26 , both of which are typically interconnected and mounted together by sliding the mounting bracket into the mounting slot  22 . However, adjacent housing modules  38  are also interconnected so that in a fully assembled filter system  10 , all of the housing modules  38  pivot together between the open position shown in  FIG. 3  and the closed position shown in  FIG. 1 . Each housing module  38  has an irregular shaped wavy front face  41  that defines three oblong cartridge openings  42 . When the housing modules  38  are pivoted to the closed position, the edge opposite the hinged connection  40  latches onto the edge of the back plate base  20  with a spring-lock connection  43  that can be manually released by the user to open the housing should it be necessary to access the filter head  26 . In the closed position of the housing  37 , the oblong cartridge openings  42  are axially aligned and axially aligned with the cradle  35  and mounting ring  25 , such that a filter cartridge  11  may be inserted axially through the mounting ring  25  and into the filter head  26 . In the mounted position, as shown in the drawings, the free end of the filter cartridge  11  is accessible to and may be conveniently grasped by the user to turn and remove the cartridge, as will be discussed in greater detail below. 
     The wavy edges  44  of the housing front face  41  are provided with connector openings  45  which, when adjacent housing modules  38  are aligned, can be connected with circular spade connectors  46 . It will be appreciated that by use of back plate edge connectors  31 , edge connectors  36  on adjacent spacer panels  33 , the hinged connection  40  for the housing module and spade connectors  46  for adjacent housing modules  38 , a very rigid assembly may be produced. Furthermore, as suggested above, the mounting openings  21  in the back plate base  20  permit the mounting of the system in virtually any orientation that provides access of the filter cartridges  11  to the user. 
     Referring now to  FIGS. 4-6 , the mounting ring  25  on the mounting bracket  24  provides attachment for the filter head  26  and a demountable support for the filter cartridge  11 . The filter head  26  also provides flow connections to and from the filter cartridge, the operative end of which is inserted axially into the filter head. The filter head includes a cylindrical top portion  47  that defines an outer housing  49  carrying a pair of oppositely extending coaxial sleeves  48  and  50  that define, respectively, the water inlet opening and water outlet opening to and from the filter head. On the interior of the filter head housing, there is mounted a flow control valve spindle, the function of which will be described in detail below. 
     The filter head outer housing  49  has a bottom cylindrical skirt having a diameter somewhat larger than the top portion  47 . The edge of the cylindrical skirt  51  is provided with a pair of diametrically opposite mounting lugs  52  and  53 . The mounting ring  25  has a generally open annular interior including an outer wall  54  sized to receive the cylindrical skirt  51  of the filter head outer housing  49 . The upper edge of the mounting ring outer wall  54  includes a pair of inwardly opening slots  55  and  56 , respectively, for receipt of the mounting lugs  52  and  53 . Mounting lug  52 , positioned below the inlet sleeve  48 , is provided with an open gap  57 . The slot  55  in the mounting ring outer wall  54  has a protrusion  58  sized to move axially through the gap  57  as the housing cylindrical skirt  51  moves axially into the mounting ring  25 . By comparison, the housing mounting lug  53  (diametrically opposite mounting lug  52 ) has no gap and the slot  56  does not have a protrusion. As a result, the filter head  26  can only be inserted into the mounting ring at one circumferential position. As the cylindrical skirt  51  of the filter head drops through the slots, the lower edge comes to rest on a circular track  60  on the interior of the mounting ring. The track  60  defines the bottom of an annular slot  61  having a height just slightly larger than the thickness of the mounting lugs  52  and  53  such that, when the filter head is rotated on the circular track  60 , the lugs  52  and  53  pass into the annular slot  61  until the filter head is in an operative position with the axis of the coaxial inlet and outlet sleeves  48  and  50  is parallel to the mounting bracket  24 , as shown in  FIG. 5 . In this position, stop detent  62  on the cylindrical skirt  51  engages a first stop  63  in the circular track  60  to prevent reverse rotation and establish the operative position of the filter head. Further, a locking detent  64  on the cylindrical skirt  51  simultaneously engages a second stop  65  on the circular track to prevent continued rotation of the filter head and to lock it in its operative position. 
     Referring to  FIG. 6 , the top portion  47  of the filter head  26  has a cylindrical interior wall  66  in which are formed diametrically opposite inlet opening  67  from the inlet sleeve  48  and outlet opening  68  to the outlet sleeve  50 . Referring also to  FIGS. 8A and 8B , the outer housing  49  of the filter head  26  houses a valve spindle  70 , the reciprocal rotary movement of which controls the flow of water into and out of the filter cartridge  11 . The filter cartridge is inserted axially through the bottom of the mounting ring  25  where a combination of vertical axial movement and rotational movement simultaneously locks the cartridge  11  onto the mounting ring  25  and rotates the spindle  70  from the off (no-flow) position to the on (flow) position. The valve spindle  70  has a cylindrical body  71  that is positioned in closely spaced coaxial relation to the cylindrical interior wall  66  of the filter head  26 . The cylindrical spindle body  71  has a pair of diametrically opposed and coaxially aligned flow ports  73  which move, with rotation of the spindle  70 , between the flow and no-flow positions to provide connection and disconnection of the inlet and outlet openings  67  and  68  in the filter head interior wall with the cartridge inlet and outlet, which will now be described. 
     The filter cartridge  11  has a body  74  with an axially extending neck  75  on one end. The neck defines an inlet  76  for water to be treated and an outlet  77  for water treated by flow through an interior filter element  78 . The neck  75  has a stepped construction including a large diameter shoulder  80  adjacent the filter body  74  that has an annular shape, but is interrupted by a pair of diametrically opposed connector lugs  81 . In cross section, the connector lugs  81  have a parallelogram shape with narrow leading and trailing edges  82 , in the rotational direction, that define cam surfaces  83 . The circular track  60  in the mounting ring  25  has a pair of diametrically opposed slots  84 , each of which has angled contact surfaces  85  that define openings through which the connector lugs  81  on the filter cartridge neck may pass. As the filter cartridge neck  75  is inserted axially into the mounting ring  25  and spindle  70 , simultaneous rotation of the cartridge to the right (in the clockwise direction) will permit the leading cam surfaces  83  on the connector lugs  81  to ride upwardly over the contact surfaces  85 , into the mounting ring  25  and onto the circular track  60 . As the connector lugs  81  reach this position, their lead edges engage the edge  86  of a slot  87  in the lower edge of the spindle  70  (see also  FIG. 10 ). Continued rotation of the filter cartridge results in rotation of the spindle from the no-flow position to the flow position. Further rotation of the spindle past the flow position is prevented by engagement of a stop  88  on the slot edge  86  with the face  90  of a shallow groove  91  formed on the inside of the filter head cylindrical skirt  51  (see  FIG. 6 ). To remove the filter cartridge  11 , as for replacement, the free end of the cartridge is grasped by the user and rotated to the left (in the counterclockwise direction), the opposite edges  82  of the connector lugs  81  engage the opposite edges  86  of the slots  87  in the edge of the spindle  70  to cause rotation of the spindle in the same direction to close the valve. When the connector lugs  81  reach the slots  84  in the mounting ring circular track  60 , the lugs drop through the slots and the cartridge moves axially out of the filter head and mounting ring. 
     Referring particularly to  FIGS. 6 ,  9  and  10 , the spindle  70  must be provided with a seal arrangement that provides a water tight interface between the outside of the cylindrical body  71  of the spindle and the cylindrical interior wall  66  of the filter head  26 . The main sealing interface is provided by an upper O-ring seal  92  and a lower O-ring seal  93 . The spindle  70  also provides an important sealing interface between the flow ports  73  in the spindle and the inlet and outlet openings  67  and  68  extending through the cylindrical interior wall  66  of the filter head and the respective inlet and outlet sleeves  48  and  50 . A dual function seal  94  is provided for each of the coaxial, diametrically opposed flow ports  73 . The seal  94  rests in a recess  95  in the body  71  of the spindle. The flow ports  73  are defined by a sleeve-like nipple  96  that is surrounded by an inner sealing rib  97  on the seal  94  such that when the inner sealing ribs are aligned with the inlet and outlet openings  67  and  68  on the inside of the filter head, flow is enabled between the filter head and the cartridge, as described above. The inner sealing rib  97  bears against the cylindrical interior wall  66  of the head to seal against leakage in the flow position. The inner sealing rib  97  is surrounded by an outer sealing rib  98  and connected thereto by an intermediate web  100  to provide a unitary seal that rests snuggly in the recess  95 . A portion of the outer sealing rib may include a part of the inner sealing rib, as shown. When the spindle  70  is rotated to the no-flow position, the outer sealing rib  98  and a portion of the inner sealing rib  97 , which together surround the intermediate web  100 , surround and cover the inlet and outlet openings  67  and  68  in the cylindrical interior wall of the filter head. The dual function seal  94  is molded from any suitable synthetic rubber sealing material and is provided with a slight curvature to match the spindle body  71  to fit snuggly in the recess  95 . 
     Referring again to  FIG. 8B , with the filter cartridge  11  operatively connected to the filter head  26 , the flow of water from the inlet sleeve  48 , through the flow port  73  in the spindle body, is directed into the cartridge inlet  76  comprising an annular passageway  101  in the cartridge neck  75 . The incoming water flows into the space between the filter body  74  interior and the outside of the filter element  78 , radially inwardly through the element and into the hollow interior  102  of the element. From the interior of the filter element, the filtered water flows upwardly into the cartridge neck  75 , out of an axial outlet passage  103 , which comprises the cartridge outlet  77 , and into the spindle  70  where it is directed out of the flow port  73  and into the outlet sleeve  50 , all as generally shown by the arrows in  FIG. 8 . In order to eliminate or substantially reduce undesirable leakage from the filter cartridge  11  after it is removed from the filter head and mounting ring, an annular porous disk  104  is placed in the annular inlet passage  101  and a circular porous disk  105  is placed in the axial outlet passage  103 . The disks preferably comprise open cell porous polypropylene bodies that are porous enough to not inhibit flow through the system under normal pressure, but which inhibit flow in the absence of pressure, as when the cartridge is removed. 
     Referring again to  FIGS. 6 ,  8 A and  8 B, as well as to  FIGS. 11 and 12  and  11 A and  12 A, an arrangement is provided to assure filter cartridge compatibility and operative connection of the cartridge to the filter head. The arrangement may also be utilized to provide a proprietary arrangement for a selected distributor or installer of filter systems in accordance with the teaching of this invention. In one embodiment, an upper adaptor ring  106  is mounted in the spindle  70  and a lower adaptor ring  107  is attached to the neck  75  of the filter cartridge  11 . The rings  106  and  107  have complementary interengaging arrangements that assure compatibility of the filter cartridge to the head. 
     In the embodiment shown in  FIGS. 11 and 12 , the upper adaptor ring  106  is secured to a shoulder  108  defined by the interface between the upper spindle body  71  and a larger diameter spindle skirt  110 . The adaptor ring  106  is provided with an integral weld flange  111  and the mounting shoulder  108  is provided with a complementary weld groove  112 . In a similar manner, the lower adaptor ring  107  is mounted on a shoulder  113  on the neck of the cartridge body  74  above the connector lugs  81 . The lower adaptor ring  107  has an integral weld flange  114  that seats in a complementary weld groove  115  in the shoulder  113 . Both rings  106  and  107  are secured to the respective shoulders  108  and  113  by spin welding, ultrasonic welding or any other suitable welding process. The exposed face of the upper adaptor ring  106  is planar, except for a pair of diametrically opposite axially extending fingers  116 . The exposed planar face of the lower adaptor ring  107  has a pair of diametrically opposite recesses  117 . The upper and lower adaptor rings are located in circumferentially precise and complementary positions such that relative rotation and axial displacement of the filter cartridge  11  as it is inserted into the spindle  70  results in receipt of the fingers  116  in the recesses  117 . The rings  106  and  107 , of course, could be reversed on the spindle and the cartridge. Selected circumferential repositioning of complementary upper and lower adaptor rings  106  and  107  may be utilized to provide a proprietary fit for selected customers. To establish a desired position and a proprietary fit, the position of the fingers  117  and recesses  118  can be varied circumferentially, using a locater  119  for the spin welding fixtures. Further, the radial position of the fingers and recesses can be changed together, e.g. to the center or inner edges of the rings to provide a wide range of proprietary fits. Proper engagement of the rings, of course, also assures compatibility of the cartridge with the filter head. 
     In another embodiment, shown in  FIGS. 6 ,  8 A,  8 B,  11 A and  12 A, the upper adaptor ring  106   a  is secured to the shoulder  108 , as described with respect to the previous embodiment. Likewise, the adaptor ring  106   a  has an integral weld flange  111   a  and the mounting shoulder  108  is provided with a complementary weld groove  112 . Similarly, the lower adaptor ring  107   a  is mounted on the shoulder  113  on the cartridge body nick about the connector lugs. The lower adaptor ring  107   a  has an integral weld flange  114   a  that seats in the complementary weld groove  115  in the shoulder  113 . Both rings  106   a  and  107   a  may be secured to the respective shoulders  108  and  113  by spin welding (or other suitable welding process). The exposed lower face of the upper adaptor ring  106   a  is non-planar and defines a pair of diametrically opposite, axially extending abutment faces  116   a.  Similarly, the exposed upper face of the lower adaptor ring  107   a  has a pair of diametrically opposite and axially extending abutment faces  117   a.  As with the previously described embodiment, the upper and lower adaptor rings  106   a  and  107   a  are located in circumferentially precise and complementary positions to ensure engagement of the abutment faces  116   a  and  117   a  when the cartridge is attached to the filter head and the mounting ring. On the upper adaptor ring  106   a , the abutment faces  116   a  are defined by protrusions  118   a  on the ring body and, on the lower adaptor ring  107   a,  the abutment faces  117   a  are defined by recesses  120   a  in the ring body. 
     A presently preferred arrangement for assuring compatibility and operative connection of the cartridge to the filter head is shown in  FIGS. 31-36 . This arrangement utilizes the same filter head  26  and spindle  70  which together are attached to and carried by mounting ring  25  on the mounting bracket  24 . Similarly, the filter head and mounting bracket are designed to accept the standard filter cartridge  11 , all as previously described. 
     Referring first to  FIG. 31 , the shoulder or end face  113  on the cartridge neck  75  is provided with a pair of diametrically opposite vertically extending unlocking pins  243 . The shoulder  113  may be provided with a circular array of holes  244  into which the reduced diameter ends  245  of the pins may be press fit. For example, if the cartridge shoulder has  14  equally spaced holes  244 , diametrically opposite pairs of pins  243  could be placed in seven different circumferential positions. 
     Alternately, the pins  243  could be formed integrally with and carried on a lower adaptor ring (not shown) similar to the adaptor ring  107   a  shown in  FIG. 8A . The adaptor ring would be attached to the cartridge shoulder  113  by ultrasonic or other welding process, as previously described. 
     Referring also to  FIG. 32 , a lowermost shoulder  246  on the spindle  70  is provided with a pattern of through bores  247  into and through which the pins  243  on the cartridge neck are permitted to pass when attaching the cartridge to the filter head  26 . The pattern of through bores  247  matches the pattern of holes  244  for unlocking pins  243 . 
     An upper adaptor ring  248  is captured between shoulder  246  on the spindle  70  and a vertically adjacent shoulder  250  on the filter head  26 . The upper adaptor ring  248  has a lower face  252  that is attached to the upper surface of the spindle shoulder  246  in a manner that causes the adaptor ring  248  to rotate with the spindle  70 , but is not fixedly attached to the spindle. However, because the ring is captured between the shoulders  246  and  250 , the lower face  252  of the adaptor ring may be selectively attached to the spindle shoulder with a diametrically opposed pair of bosses  253  that are received in recesses  254  in the spindle shoulder  246 . The recesses  254  are provided in a full circumferential pattern corresponding to the circular pattern of through bores  247  in the spindle. 
     The adaptor ring  248  has a pair of diametrically opposed through holes  256  into which locking detents  257 , in the form of spring biased pins  258  extend. The locking pins  258  are mounted in blind bores  260  in the lower face  259  of the housing shoulder  250 . The blind bores  260  are formed in a circular pattern that matches, in number and spacing, the pattern of through bores  247  and the recesses  254  in the spindle shoulder  246 . The position of the pair of spring biased pins  258  on the face  259  of the shoulder is selected to correspond to the location of the through holes  256  in the adaptor ring  248  and the location of the pair of pins  243  on the cartridge neck  75 . When the locking pins  258  extend through the holes  256  in the upper adaptor ring, as best seen in  FIG. 31 , the spindle  70  cannot turn axially in the head  26 . This, of course, prevents attachment and operative engagement between the filter cartridge and the head. 
       FIGS. 31 ,  32  and  34  show the progression of unlocking the locking pins  258  by insertion of the filter cartridge with the cartridge unlocking pins  243  properly oriented circumferentially to match the adaptor ring holes  256  and the position of the pair of locking pins  258 . As the filter cartridge  11  moves vertically through the mounting ring  25  and into the spindle  70 , the pins  243  will be received and pass into the through bores  247  in the spindle. Because, as previously explained, connection of the filter cartridge to the spindle and head follows a path of simultaneous rotational and axial movement, the lower surfaces of the through holes  247  are provided with ramp surfaces  261  to permit smooth transition of the pins  243  into and through the bores  247 . The ends of the pins  243  pass into relieved areas  262  in the bottom ends of the through holes  256  in the adaptor ring and engage the ends of locking pins  258 , forcing the locking pins to move vertically upwardly against the bias of the bias springs  263 . Continued axial rotation of the spindle and adaptor ring causes the ring to under ride the ends of the locking pins  258 , forcing the pins to ride upwardly over the chamfered edges  264  of the adaptor ring, until the locking pins are fully withdrawn from the holes and ride on the upper surface  255  of the adaptor ring. 
     To assure compatibility of the cartridge with the filter head and/or to provide a proprietary arrangement for a selected customer or user, circumferential positions of the pins  243  and adaptor ring holes  256 , are selected to match the circumferential positions of the blind bores  260  in which the pair of locking pins  258  are mounted. As indicated above, with a pattern of holes  247  in the spindle shoulder  246  of  14  holes, the cartridge pin pair  246  can be matched with the locking pin pair  258  to provide 7 different positions for a proprietary fit. Hole patterns with more or fewer arrangements may be used and, to increase the number of matching fits between the cartridge and the head, the cross sectional shapes of the pins  243  and receiving holes  247  could also be varied. 
     If one of the filter cartridges  11  is a reverse osmosis (RO) cartridge, such as second cartridge  16  in the filter system  10  shown in  FIG. 1 , all of the basic elements including the filter head, spindle, mounting ring and cartridge are of different constructions than the corresponding elements in the system described thus far. The need for different size and shape of the parts for an RO system is related to the need to handle three separate flows of water, namely, the inlet water to be treated by membrane separation, the product water or permeate after passage through the membrane, and the brine or retentate carrying the dissolved solids in a relatively high volume of water. 
     Referring initially to  FIGS. 13 ,  14 , and  19 , an RO cartridge  121  has a generally cylindrical body  122  carrying a cylindrical filter element  123  and having a neck  124  on one end by which it is fastened to a mounting ring  125  and filter head  126 . The filter head  126  carries a valve spindle  127  that provides a flow control function in a manner similar to the spindle  70  of the previously described embodiment. However, the RO spindle  127  also provides a flow path for the brine flow and a control valve for regulating the flow of product water to and from a storage tank. 
     The RO unit is supported on a mounting bracket  128  with the same rectangular base permitting direct attachment to a modular back plate  18  described above. The mounting bracket  128  also includes the integral mounting ring  125  that provides attachment of the filter head  126  and spindle  127  from above and the demountable attachment of the RO cartridge  121  from below in a manner similar to the mounting arrangement used with the previously described embodiment. However, this filter arrangement also provides for the separate removal of the spindle  127 , after removal of the filter cartridge  121 , as will be described in greater detail below. 
     The RO cartridge  121  may be of a generally well known construction, including an interior spirally wound semi-permeable membrane  131  that includes an intermediate separator layer wound around a central hollow product water tube  132 . The product water flows radially inwardly, enters the product water tube  132  through holes therein, and then flows vertically upwardly along the interior of the tube and into the RO filter head  126 . The brine flow (high volume membrane concentrate of water and dissolved solids) which does not pass through the membrane, flows vertically downwardly and exits the filter element  123  at the bottom end. The volume of brine may comprise as much as 80% of the total incoming flow volume of pre-filtered water, but the proportions may change depending on other changes in system operation. 
     The upper end of the RO filter element  123  is enclosed with an end cap  134 . The end cap  134  functions to help control the flow of water through cartridge  121  and also provides a positioning function to assure proper cartridge fit and function in a manner similar to the previously described embodiment. 
     Incoming water enters the filter head  126  via an inlet sleeve  135 . With the spindle  127  rotated to the open or flow position, incoming water passes from the inlet sleeve  135  through an inlet opening  136  in the wall of the filter head  126 , and continues through an inlet  137  in the spindle  127 . System pressure acts on one diaphragm of a double diaphragm valve  138 , causing it to unseat and to permit incoming water to flow vertically downwardly through an inlet passage  140  and through an opening in the end cap  134  of the filter element  123 . The water then passes through the RO filter element  123 , as previously described, where it is divided into a product water (permeate) flow and a brine (retentate) flow. These two flows are returned to the filter head via the spindle  127  for further processing as follows. 
     Referring particularly to  FIG. 14 , the lower end of the spindle  127  has a downwardly depending outer skirt  141  that seals against the outside of the cartridge neck  124  and against the inside of end cap  134 . An intermediate skirt  142 , coaxial with the outer skirt  141 , provides a flow channel for water from the inlet  137 . A brine flow passage  143  ( FIG. 15A ) on the outside of the outer skirt  141  provides an inlet to the spindle for brine exiting the filter. The intermediate skirt  142  is sealed on the inside to the outside of the product water tube  132 . A spindle inner skirt  144  has, in its lower inlet end, a porous polypropylene disk  145  that provides the same anti-drip function as the disks  104  and  105  described for the prior embodiment. Above the porous disk is a check valve  146  that prevents the back flow of treated product water into the RO cartridge  121 , as will be described in great detail below. The product water flows through a vertical product water passage  147 , a cross passage  149  in a removable closure plate  153 , and then vertically into a chamber  148  in the closure plate  153  where the product water is exposed to the face of the outside diaphragm  154  of the double diaphragm  138 . From the chamber  148 , the product water flows through an outlet  150  in the closure plate  153 , and an outlet opening  151  in the filter head, which opens directly to the outlet sleeve  152 . 
     The higher volume brine flow, passing out of the RO cartridge  121  between the cartridge neck  124  and the outside of the spindle outer skirt  141  passes into the spindle body via the radial passage  143  in the upper portion of the outer skirt  141 . The radial passage  143  joins a vertical passage  156  into the spindle body to a second radial passage  157  where the brine flow exits the spindle body and enters a large open area chamber  160  between the spindle body and the inside wall of the filter head  126 . The brine flow continues generally vertically to a radial outlet passage  158  where the brine flow exits the large open area and re-enters the spindle body via an outlet passage  158  that communicates with an open upper chamber  161  at the top of the spindle  127 . The upper chamber is sealed from the large open brine-containing chamber  160  below and is enclosed by a filter head top cap  162 . Brine flow exits the upper chamber  161  via a brine outlet opening  163  in the filter head and an integral brine outlet sleeve  164 . 
     Returning again to  FIGS. 13 and 14 , the flow of product water exiting the filter head  26  via the outlet sleeve  152  may be directed to a pressurized storage tank in a manner well known in the art. The storage tank typically includes an interior flexible bladder or wall to one side of which the product water flows and on the other side of which is an air space. As product water fills the storage tank and presses against the flexible bladder, the air on the opposite side is compressed and, therefore, the purified product water is stored under pressure. Other means for pressurizing the stored product water are also known. When the pressure in the storage tank reaches a desired level, the storage back pressure acts on the outside diaphragm  154  of the double diaphragm valve  138  to overcome the counter-pressure of pre-filtered inlet flow against the opposite inside diaphragm  139 , causing the latter to move against its seat and to shut off the incoming flow from the inlet sleeve  135 . As is known in the art, the areas of the respective inside and outside diaphragms  139  and  154  may be chosen to match a desired maximum storage tank pressure to the usual incoming line pressure, e.g. the pressure of the municipal supply of water. With a typical municipal water supply pressure of 60 psi and a desired storage tank pressure of 40 psi, the area of the outside diaphragm  154 , exposed to storage tank pressure, would be about two-thirds the area of the inside diaphragm  139 , exposed to incoming line pressure. At about 40 psi of storage tank pressure, the 60 psi inlet line pressure would be overcome and the shut off valve  46  would close. 
     The radial outlet passage  158  from which brine flows out of the large open chamber  160  between the outside of the spindle and the inside of the filter head  126  is provided with a flow restrictor  165 . The flow restricted may be of any convenient construction which will create a brine back pressure sufficient to cause a desired volume of water to be forced through the RO membrane to generate the product water permeate. For example, the restrictor may comprise a ball valve and seat which is slotted to permit a restricted flow of brine past it. Generally, a ratio of brine-to-product water of about 5:1 to 4:1 is desirable. The ratio will vary from initial start up as the increasing permeate back pressure from the pressurized storage tank counters inlet line pressure, thereby reducing permeate flow volume somewhat. 
     Referring also to  FIGS. 16 and 17 , the RO cartridge  121  and RO filter head  126  require a different mounting bracket  128  and integral mounting ring  125  than are used with the previously described filter cartridge  11  and filter head  26 . However, the differences are primarily in size and, as will be described, the RO cartridge  121  and associated filter head  126  are attached to the RO mounting ring  125  in substantially the same way. The mounting bracket  128  is attached to the same back plate  18  to provide the modular assembly of a filter system as is the previously described mounting bracket  24 . 
     The RO filter head  126  has an outer housing  168  that includes a cylindrical bottom skirt  170  having an outer diameter larger than the upper portion of the outer housing  168 . The lower edge of the cylindrical skirt  170  is provided with a pair of diametrically opposite mounting lugs  171  and  172 . The mounting ring  125  has a generally open annular interior, including an outer wall  173  sized to receive the cylindrical bottom skirt  170  of the filter head housing. The upper edge of the mounting ring outer wall  173  includes a pair of inwardly opening slots  174  and  175 , respectively, for receipt of the mounting lugs  171  and  172 . Mounting lug  171 , which is positioned below the inlet sleeve  135 , is provided with an open gap  176 . The slot  174  in the mounting ring outer wall  173  has a protrusion  177  that is sized to move axially through the gap  176  as the housing cylindrical skirt  170  moves axially into the mounting ring  125 . The opposite mounting lug  172  has no gap and the corresponding slot  175  does not have a protrusion. As a result, the filter head  126  can only be inserted into the mounting ring at one circumferential position. As the cylindrical bottom skirt  170  of the filter head drops through the slots, the lower edge comes to rest on a circular track  178  on the interior of the mounting ring. The track  178  defines the bottom of an annular slot  180  having a height just larger than the thickness of the mounting lugs  171  and  172 , such that when the filter head is rotated on the circular track  178 , the lugs  171  and  172  pass into the annular slot  180  until the filter head is in the operative position with the axis of the coaxial inlet and outlet sleeves  135  and  152  parallel to the mounting bracket  128 . In this operative position, a pair of diametrically opposite stop detents  181  on the outer surface of the cylindrical skirt  170  engage respective first stops  182  in the circular track  178  to prevent reverse rotation and establish the operative position of the filter head. Further, a pair of diametrically opposite locking detents  183  on the cylindrical skirt  170  immediately above the mounting lugs  171  and  172  engage respective second stops  184  on the circular track to prevent continued rotation of the filter head and to lock it in its operative position. Preferably, the stop detents  181  have ramped surfaces permitting them to ride along the circular track  178  under the force of manual rotation of the filter head in the mounting ring until the stop detents  181  snap into engagement with their respective stops  182 . In this position, the locking detents  183  reach and simultaneously engage the second stops  184  establishing the locked operative position of the filter head. 
     The RO filter head  126  is made to permit removal of the spindle  127  in the event it is necessary to replace the double diaphragm shut off valve  138 . The following comments describe first how the RO spindle  127  is mounted in the filter head  126  and how the RO filter cartridge  121  is attached to the mounting ring  125  and operatively connected to the filter head and spindle. The upper end of the spindle  127  is provided with an annular locking groove  185  (see  FIGS. 13 and 14 ) positioned immediately above an upper O-ring seal  186  that seals the upper chamber  161  from the large open area chamber  160  below. Similarly, a lower O-ring seal  187  provides a sealed interface between the spindle and the interior of the filter head  126 , thereby sealing the vertical chamber  160  surrounding the spindle  127 . That chamber also includes the water inlet  137  and the axially aligned outlet  150 , the latter of which, as described above, is actually formed in the closure plate  153 . The body of the spindle  127  is provided with a seal arrangement that creates a water tight interface between the spindle body and the cylindrical interior wall  188  of the filter head  126 . In addition to the upper and lower O-ring seals  186  and  187 , the sealed interface includes a dual function seal  190  for each of the inlet  137  and outlet  150  in the spindle and the corresponding respective inlet opening  136  and outlet opening  151  in the filter head  126 . The dual function seal  190  is similar in construction and function to the seal  94  (see  FIG. 10 ) used in the previously described embodiment. Thus, the dual function seal  190  rotates with the spindle  127  between a flow position, wherein flow is enabled between the filter head and the cartridge as described above, and a no-flow position, wherein flow is halted. In both positions, the dual function seal separates the brine flow through the filter head and spindle from the flows of incoming water and product water. 
     Because the spindle  127  is designed to be removable for replacement of the diaphragm shut off valve  138 , it is possible to mount the filter head  126  to the mounting ring  125  with or without the spindle in place in the filter head. With the filter head  126  mounted in operative position to the mounting ring  125 , as described above, the spindle  127  is inserted axially from below through the mounting ring  125  and into the filter head  126 . Referring also to  FIG. 20 , the annular locking groove  185  in the upper end of the spindle is provided with an open notch  191  sized to receive a lug  192  on the inside wall of the filter head  126  just below the brine outlet opening  163 . Receipt of the lug  192  in the notch  191  permits the spindle to be fully inserted and the lug  192  aligned with the annular locking groove  185 . Rotation of the spindle causes the locking groove to enclose the lug such that the spindle is restrained from axial movement out of the filter head. The spindle may be rotated with respect to the head and the lug  192  until the lug engages a stop  193  in the locking groove  185  after about 120° of rotation. This places the spindle rotationally in the no-flow position whereupon the system water may be turned on to permit operation. 
     Referring also to  FIGS. 16-18 , the neck  124  of the RO cartridge  121  is provided with a pair of diametrically opposed connector lugs  194 , similar to the connector lugs  81  (see  FIG. 8A ) of the previously described embodiment. The connector lugs  194  have a parallelogram shape in cross section defined by narrow leading and trailing edges  195 , in the rotational direction, that define cam surfaces  196 . The circular track  178  in the outer wall  173  of the mounting ring  125  has a pair of diametrically opposed slots  197 , each of which has angled contact surfaces  198  that define openings through which the connector lugs  194  on the filter cartridge neck may pass. As the filter cartridge neck is inserted axially into the mounting ring and spindle, simultaneous rotation of the cartridge to the right (clockwise direction) permits the leading cam surfaces  196  on the connector lugs to ride upwardly over the contact surfaces  198 , into the mounting ring  125  and onto the circular track  178 . As the connector lugs reach this position, their lead edges engages the vertical drive faces  200  of a rotatable spindle drive ring  201  ( FIG. 21 ) that is captured in the interface between the filter head outer housing  168 , the mounting ring  125  and the spindle  127 . More particularly, and referring also to  FIGS. 14 ,  15 A and  15 B, the spindle drive ring  201  rests on an annular shoulder  202  on the cylindrical interior wall  188  of the filter head  126 . The drive ring  201  carries an upper O-ring seal  203  that seals against the cylindrical inner wall  188  of the filter head. The interface between the drive ring and the spindle is sealed by the lower O-ring seal  187 . A lower flange  205  on the spindle that defines one wall of the groove carrying the lower O-ring seal  187  is provided with a pair of diametrically opposite drive tabs  204  ( FIGS. 20 and 26 ). With the drive ring  201  seated on the shoulder  202 , insertion of the spindle through the drive ring and into the filter head permits the drive tabs  204  to drop into shallow notches  206  in the interior of the drive ring. If necessary, continued rotation of the spindle and the drive ring will permit the notch  191  in the annular locking groove  185  at the upper end of the spindle to engage the lug  192  on the interior of the filter head to establish the proper axial position of the spindle within the head and the drive tabs  204  to seat fully in the notches  206 . From this position, axial rotation of the spindle and drive ring in the counterclockwise direction (clockwise rotation is prevented by stop wall  199  in the locking groove  185  at one side of the notch  191 ) permits the annular locking groove  185  in which the lug  192  is seated to move relative to the lug until the lug reaches the stop  193  in the groove  185  after about 120° of rotation. At this position, the spindle is in the no-flow position and the supply of water may be turned on. As the filter cartridge  121  is inserted vertically through the tapered slots  197  in the mounting ring  125  and onto the circular track  178 , the lead edges of the lugs will engage the vertical drive faces  200  on the spindle drive ring to cause rotation of the spindle from the no-flow to the flow position. Continued movement in the clockwise direction is prevented by engagement of the lead edges  195  of the connector lugs  194  with recessed stops  189  inside of the bottom edge of the filter head bottom skirt  170 . In this position, the lowermost edges  207  of the spindle drive ring  201  rest on the circular track  178  and the recessed edges  209  rest on the top surfaces of the cartridge connector lugs  194 . 
     Referring again to  FIGS. 13 ,  15 A and  15 C, as well as  FIGS. 22-25 , the RO filter cartridge  121  contains the filter element  123  that is inserted through the open bottom end of the cartridge body  122  and held in place with a lower enclosing end cap  207 . The upper end of the filter element  123  is closed by the end cap  134  that has an outer flange  208  that is seated in the upper end of a brine ring  210  and sealed therein with an O-ring seal  211 . The upper end of the end cap  134  has a narrower neck  212 , the outside of which seats an upper O-ring  213  that provides sealing contact with the inside of the outer skirt  141  of the spindle  127  when the cartridge is inserted through the mounting ring and into the filter head. The O-ring seals  211  and  213  preclude brine water from mixing with the incoming water and product water, and assure that the brine flow is directed to the brine flow passage  143  in the spindle outer skirt  141 . Separation of the incoming water flow from the product water flow is accomplished by a double O-ring seal  214  carried on the product water tube  132  that engages the inside surface of the spindle inner skirt  144 . 
     The RO cartridge  121  and valve spindle  127  include a locator arrangement, similar to that used in the previously described embodiment, to assure filter cartridge compatibility and operative connection of the cartridge  121  to the filter head  126 . This arrangement may also be utilized to provide a proprietary filter assembly for a selected distributor or dealer, as also previously described above. 
     A lower adaptor ring  215  ( FIGS. 23 and 24 ) seats on an interior shoulder  216  on the inside of the neck  212  of the end cap  134 . The ring  215  has an integral finger  217  extending perpendicular to the plane of the ring. The ring may be secured on the interior shoulder  216  by spin welding, ultrasonic welding or other suitable fastening process. The end cap outer flange  208  is provided with a locator notch  218 . Upon assembly of the filter element  123  into the cartridge body  122 , the locator notch  218  is positioned to engage a matching protrusion on the inside of the neck  124  of the filter cartridge body. This assures proper circumferential location of the finger  217 . A complementary upper adaptor ring  220  ( FIGS. 25 and 26 ) is seated on a shoulder  221  on the inside of the spindle outer skirt  141 . The inside edge of the upper adaptor ring  220  is provided with a circumferentially extending cutout  223  which, in turn, has a centered notch  222  that is sized to receive the finger  217  extending from the lower adaptor ring  215 . The upper adaptor ring  220  may also be affixed on the shoulder  221  by spin welding or other suitable plastic welding process that positions the notch  222  such that, when the cartridge is attached to the filter head with the spindle  127  in the locked off position, the finger  217  will engage the notch  222 . By adjusting the circumferential positions of the finger  217  and the notch  222 . By accurate control of the welding process, a number of proprietary adaptor ring positions may be provided that can be used to offer a customer a proprietary product. 
     Referring particularly to  FIGS. 13 ,  26  and  27 , when it is desired to remove the spindle  127  to, for example, replace the diaphragm valve  138 , it has been found that the many sealed interfaces between the spindle and the head  126  make it difficult to remove the spindle. To facilitate spindle removal, a special spindle removal tool  224 , as shown in  FIG. 27 , may be used. After the RO cartridge  121  has been removed and the source of water has been shut off, the removal tool  224  is inserted into the spindle with the inner spindle skirt  144  received in the hollow interior of the tool body  225 . A curved offset  226  on the inner end of the tool body is sized to fit into the cutout  223  in the adaptor ring  220 . When the curved offset  226  is centered in the cutout, engagement lug  227  at the end of the offset  226  will pass through the notch  222  in the cutout  223 . Slight rotation of the tool in either direction will cause the engagement lug  227  to move out of alignment with the notch  222  and to engage the underside of the ring  220 . The user may then pull axially on the tool handle  228 , after first rotating the tool in the “on” direction to permit the retaining lug  192  in the upper part of the filter head  126  to pass through the notch  191  in the locking groove  185 . 
     To further facilitate removal of the spindle  127  from the filter head  126 , and referring also to  FIG. 17 , a large portion of the cylindrical interior wall  188  of the filter head has a recessed cylindrical surface  229  that has a larger diameter than the sealing surfaces  219  that make sealing contact with the dual function seal  190 . When the spindle is rotated to the removal position, dual function seals  190  will engage the recessed surface where the force necessary to remove the spindle is substantially reduced. 
     Referring to  FIG. 8B  and also to  FIGS. 28-30 , the filter element  78  is assembled into the cartridge  11  utilizing a unique filter element positioning and stabilizing method. The filter element  78 , which may comprise a granular activated carbon or porous carbon block filter element is inserted axially through a bottom opening  230  in the cartridge body  74 . The filter element  78  has an upper end cap  231  that engages the inside of the cartridge neck  75 . Specifically, the upper end cap  231  engages four equally spaced circular flats  232  to provide a stop to further axial movement in the upward direction. The filter element  78  is secured within the cartridge body  74  with a bottom end cap  233  that, in the preferred embodiment, is spin welded to the bottom opening  230 . The bottom end cap  233  has a centering post  239  that engages a center recess  241  in an end closure  242  of the filter element  78 . In order to facilitate spin welding, it is desirable to attach the bottom end cap with the filter cartridge assembly positioned vertically. This, in turn, requires that the filter element  78  be retained against downward vertical movement until the bottom end cap  233  has been successfully spin welded to the opening  230  in the cartridge body  74 . The upper end cap  231  includes an upwardly extending filter neck  234  that defines the water inlet  76  and outlet  77 , the upper end of the former provided with an upper O-ring seal  235  that engages the interior of the spindle body  71 . The lower portion of the filter neck  234  is provided with a lower O-ring seal  236  that provides sealing contact with the interior of cartridge body neck  75 . To retain the filter element  78  for the spin welding process, after insertion of the element axially into the filter body against the flats  232 , a retaining ring  237  is inserted in a circular groove  238  in the portion of the neck just above the upper end of the cartridge body neck  75 . The groove  238  for the retaining ring  237  is shallow and results in the retaining ring extending radially over the inner edge of the top end of the neck  75 . The retaining ring  237  provides a positive stop against reverse axial downward movement of the element in the cartridge body, thereby enabling the spin weld process to fully and securely enclose the bottom of the cartridge. The retaining ring  237  provides no sealing function and may be left in place when the cartridge is attached to the filter head  26 . 
     The cartridge bottom end cap  233  is preferably partially enclosed by a cap grip ring  240  that is snapped over the peripheral edge of the bottom end cap. The grip ring  240  is made of a softer rubber-like plastic to facilitate gripping by the user for cartridge installation or removal. Further, the grip ring  240  may be colored to provide a code to assist the user in selecting and installing the proper filter cartridge.