Patent Publication Number: US-11383992-B2

Title: Water purification system with automatic flush flow

Description:
CROSS-REFERENCE TO RELATED APPLICATION DATA 
     The present application is a continuation of U.S. patent application Ser. No. 16/047,177 filed on Jul. 27, 2018, which is a continuation of U.S. patent application Ser. No. 14/575,965 filed on Dec. 18, 2014, which claims priority to U.S. Provisional Patent Application No. 61/917,835 filed on Dec. 18, 2013, all of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to improvements in water purification systems of the type having a reverse osmosis (RO) unit or the like for removing dissolved ionic material and other contaminants from an ordinary supply of tap water or the like. More particularly, the present invention relates to an improved water purification system having automatic flush flow for intermittently and automatically self-cleaning a reverse osmosis membrane and refreshing particulate catalyst matter in related pre- or post-filters. 
     Water purification systems in general are well-known in the art of the type having a reverse osmosis (RO) unit or membrane for converting an incoming supply of ordinary tap or feed water into relatively purified water for use in cooking, drinking, etc. In general terms, the reverse osmosis unit includes a semi-permeable RO membrane through which a portion of the tap water supply passes, such that the membrane acts essentially as a filter to remove dissolved metallic ions and the like as well as other contaminants and undesired particulate matter from the tap water. In normal operation, these impurities are removed from one portion of the water flow and concentrated in another portion of the water flow, commonly referred to as retentate or brine, which is normally discharged as waste to a drain. The thus-produced flow of relatively purified water is available for immediate dispensing for use, and/or for temporary storage within a suitable reservoir or vessel for later dispensing. 
     A pure water dispense faucet mounted typically on or adjacent to a kitchen-type sink or the like is manually operable to dispense the produced purified water. While the specific construction and operation of such RO water purification systems may vary, such systems are exemplified by those shown and described in U.S. Pat. Nos. 4,585,554; 4,595,497; 4,657,674; and 5,045,197. 
     One disadvantage associated with reverse osmosis water purification systems relates to the fact that retentate or brine outflow from the RO membrane is normally discarded as waste. As a result, many residential and commercial water customers have favored use of bottled water as a purified water source, despite the costs and inconveniences associated with delivery, storage and changeover of large (typically 5 gallon) water bottles with respect to a bottled water cooler. 
     Another disadvantage associated with reverse osmosis water purification systems relates to the typically limited service life of the RO membrane and other pre- and post-filter elements. Many RO systems use a pre-filter element typically including a carbon-based filtration media for initial removal of contaminants from a tap water inflow at a location upstream from the RO membrane. One important function of this pre-filter element is to remove contaminants that would otherwise shorten the operating service life of the RO membrane. A downstream-located post-filter element is also commonly provided for additional water filtration and purification before dispensing. This array of pre- and post-filter elements, in combination with the RO membrane, is often provided in the form of individual cartridges designed for facilitated disassembly from and re-assembly with a unitary-type manifold. See, for example, U.S. Pat. No. 5,045,197, the contents of which are herein incorporated by reference. Despite the fact that cartridge replacement may be required only once each year, and despite efforts to make cartridge changeover an intuitively simple process, many customers are reluctant to handle this task. Instead, replacement of the various RO system cartridges has largely remained the responsibility of a water service company, thereby entailing regular and relatively costly service calls to each customer&#39;s residence or place of business. The requirement for regular service calls dramatically increases the overall operating cost of the RO system, thereby reducing or eliminating apparent advantages relative to conventional bottled water coolers and related bottle delivery systems. 
     There exists, therefore, a significant need in the art for further improvements in and to water purification systems, wherein the service life of a reverse osmosis (RO) membrane and/or related pre- or post-filter elements are significantly extended for at least a period of several years without requiring attention by service personnel through. Such improvements include the use of a flush-flow activation chamber that intermittently facilitates rapid injection of tap water inflow over the RO membrane to wash away accumulated particulate matter and to refresh particulate catalyst matter in pre- or post-filtration cartridges that may clump together during periods of relatively slow tap water inflow. The present invention fulfills these needs and provides further related advantages. 
     SUMMARY OF THE INVENTION 
     The water purification system with automatic flush flow disclosed herein includes a water purification unit having a tap water inflow port for receiving a tap water inflow from a water supply system to produce a supply of relatively purified water discharged from said unit via a purified water outflow port, and a brine water outflow having impurities concentrated therein and discharged from said unit via a brine outflow port. The purification unit also includes an RO filter having an RO membrane for separating relatively unfiltered water flow into the purified water and brine water outflows. A flush flow activation chamber fluidly coupled to the brine water outflow has a plunger that substantially occludes the brine water outflow through the brine outflow port when in a first seated position, and substantially permits brine water outflow to exit the purification unit through the brine outflow port when in a second unseated position. The activation chamber generates back pressure within the water purification system to flash flow tap water inflow into the purification unit and through the RO membrane when the plunger moves from the first position to the second position, thereby substantially refreshing said RO membrane. 
     Further with respect to the flush flow activation chamber, the plunger is generally an elongated cylindrical body having a substantially frusto-conical head sized for at least partial insertion into a seat adjacent the brine outflow port. This frusto-conical head includes a slot that permits brine water outflow through the brine water outflow port when the plunger is in the first seated position. Additionally, the plunger may also include a fin that at least partially increases fluid turbulence within the activation chamber for increasing activation back pressure, which may beneficially increase cleaning across the RO membrane. 
     Additionally, the purification unit may further include a pre-filter coupled between the tap water inflow port and the RO filter. The pre-filter preferably includes a solid carbon media for suspending impurities from said tap water inflow before delivery to the RO filter. The purification unit may also include a post-filter coupled between the RO filter and the purified water outflow port, wherein the post-filter includes a particulate catalyst media that preferably includes zinc. 
     The aforementioned purification unit may also be in the form of a multi-cartridge unit that includes an RO filter cartridge and a catalyst media cartridge and is adapted for unidirectional installation within a manifold housing. In this respect, the manifold housing and multi-cartridge unit may include inter-engageable ported members for sealed fluid-coupled engagement when the multi-cartridge unit is installed into said manifold housing. The manifold housing may carry the manifold base of the multi-cartridge unit in a slide unit configured for removable unidirectional seated installation, wherein the slide unit is movable between an extended position permitting access to and removal and replacement of the multi-cartridge unit, and a retracted position with the inter-engageable ported members in sealed fluid-coupled engagement. The water purification system, and specifically the manifold housing, may be coupled to a faucet via the purified water outflow port, for dispensing the produced purified water. 
     In another embodiment, the water purification system with automatic flush flow produces a supply of relatively purified water and a supply of brine water having impurities concentrated therein through use of a multi-cartridge unit having a manifold base with a tap water inflow port for receiving a tap water inflow from a water supply system, and a purified water outflow port and a brine outflow port for respectively discharging the purified water and brine water out from the multi-cartridge unit. In this embodiment, an RO filter cartridge is in flow-coupled relation with the manifold base and includes an RO membrane for separating the tap water inflow into purified water and brine water. A post-membrane cartridge in flow coupled relation with the manifold base between the RO filter and purified water outflow port houses a particulate catalyst media that preferably includes some zinc, to further purify the water being dispensed for consumption. The flush flow activation chamber is in flow-coupled relation with the brine water and has a throttle for substantially occluding brine water outflow to the brine outflow port when in a first position, and substantially permits brine water outflow to exit the multi-cartridge unit through the brine outflow port when in a second position. In this respect, the activation chamber generates back pressure within the water purification system to flash flow water through the RO filter cartridge and over the RO membrane sufficient to wash the membrane surface and sufficient to agitate and stir the particulate catalyst media when the throttle moves from the first position to the second position. 
     The throttle may include a slot formed from a portion of a substantially frusto-conical head to permit brine water outflow through the brine water outflow port when the throttle is in the aforementioned first position. To increase the threshold activation back pressure, the throttle may also include a radially outwardly projecting fin configured to resist movement from the first position to the second position. 
     The multi-cartridge unit may also include a pre-membrane cartridge in flow-coupled relation with the manifold base between the tap water inflow port and RO filter, and include a solid carbon media for suspending impurities from the tap water inflow. The multi-cartridge unit may also be adapted for removable unidirectional seated installation within a slide unit of a manifold housing, with the slide unit being movable between an extended position permitting access to and removal and replacement of the multi-cartridge unit, and a retracted position. The manifold housing and multi-cartridge unit preferably further include inter-engageable ported members for sealed fluid-coupled engagement when the multi-cartridge unit is installed into the manifold housing. Pure water may be dispensed out through the manifold housing to a faucet for consumption. 
     In another alternative embodiment described herein, a reusable multi-cartridge water purification unit with automatic flush flow is configured for unidirectional installation into a water purification system, and includes a manifold base having a tap water inflow port for receiving a tap water inflow from a water supply system, a purified water outflow port for discharging a relatively pure water outflow, and a brine outflow port for discharging a supply of brine water outflow having impurities concentrated therein. The multi-cartridge unit further includes a pre-membrane cartridge in flow-coupled relation with the tap water inflow and includes a carbon media for suspending impurities from said tap water inflow, a post-membrane cartridge including a particulate catalyst media (e.g., including zinc) in flow-coupled relation between an RO filter and purified water outflow port, and an RO water filtration cartridge having an RO membrane in flow-coupled relation with the manifold base between the pre- and post-membrane cartridges. The RO water filtration cartridge also includes a flush flow mechanism having a plunger therein substantially occluding brine water outflow when in a closed position, and substantially permitting brine water outflow when in an open position. 
     The plunger moves between the closed and open positions in response to a back pressure within the multi-cartridge unit. In this respect, the plunger effectively releases the back pressure at some threshold pressure by being pulled out from the closed position. This permits a flash flow of water over the RO membrane and through the particulate catalyst. To this end, the plunger may include a fin for increasing said threshold pressure. This mechanism substantially refreshes the RO membrane and stirs the particulate catalyst to prevent channeling. The plunger may include an elongated cylindrical body having a substantially frusto-conical head sized to occlude the brine outflow port. Additionally, the plunger may also include a slot formed from the frusto-conical head to permit brine water outflow through the brine water outflow port when the plunger is in the closed position. The flash flow of water through the post-membrane cartridge is sufficient to lift and turbulently stir the particulate catalyst media inside in a manner to remove an oxidation layer thereon and for flushing this removed oxidation layer out from the post-membrane cartridge. This feature of the water purification system effectively refreshes the particulate catalyst media. 
     The water purification system may also include a manifold housing that includes a slide unit for unidirectional receipt of the multi-cartridge unit. 
     Here, the slide unit is movable between an extended position permitting access to and removal and replacement of the multi-cartridge unit, and a retracted position with the multi-cartridge unit housed within the manifold housing. The manifold housing and multi-cartridge unit preferably include inter-engageable ported members for sealed fluid-coupled engagement when the multi-cartridge unit is installed into said manifold housing, e.g., when in the “retracted” position. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in connection with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate the invention. In such drawings: 
         FIG. 1  is a schematic diagram illustrating deployment of a water purification system in accordance with the present invention; 
         FIG. 2  is an enlarged perspective view showing an exemplary manifold housing of the water purification system; 
         FIG. 3  is a partially exploded perspective view of the manifold housing of  FIG. 2 , with a housing cover removed to illustrate the internally mounted components, and specifically illustrating a slidable drawer in an open position and showing a selectively removable multi-cartridge unit in exploded relation therewith; 
         FIG. 4  is an enlarged perspective view of the manifold housing similar to  FIG. 3 , illustrating the slidably retractable drawer carrying the removably mounted multi-cartridge unit; 
         FIG. 5  is an alternative perspective view of the manifold housing similar to  FIG. 4 , with the housing cover removed and showing the slidable drawer with multi-cartridge unit in a fully installed position; 
         FIG. 6  is an enlarged fragmented cross-sectional view taken generally on the line  6 - 6  of  FIG. 5 , illustrating the multi-cartridge unit fluidly coupled to the manifold housing; 
         FIG. 7  is a vertical sectional view taken generally on the line  7 - 7  of  FIG. 5 , illustrating the internal components of the multi-cartridge unit and manifold housing; 
         FIG. 8  is a schematic flow diagram indicating water flow through the manifold housing and the multi-cartridge unit when removably installed therein; 
         FIG. 9  is a partial exploded perspective view of the cartridge carrier housings relative to the respective cartridge carriers formed in the manifold base; 
         FIG. 10  is a top planar view of the cartridge carrier taken about the line  10 - 10  in  FIG. 9 , and further illustrating the flow paths within the manifold base that couple to the RO filtration cartridge, the pre-membrane cartridge and post-membrane cartridge; 
         FIG. 11  is a partial exploded perspective view similar to  FIG. 9 , with the cartridge carrier housings removed to show the internal water filtration equipment therein, including the RO filter with flush-flow activation chamber, carbon-based pre-filter and particulate catalyst post-filter in relation to the respective cartridge carriers of the manifold base; 
         FIG. 12  is a perspective view similar to  FIG. 11 , illustrating installation of the RO filter and flush-flow activation chamber, the carbon-based pre-filter and the particulate catalyst post-filter in the manifold base; 
         FIG. 13  is a cross-sectional view taken about the line  13 - 13  in  FIG. 5 , illustrating the internal flow characteristics of the water purification system through the carbon-based pre-filter, the RO filter, and particulate catalyst post-filter as coupled to the unitary manifold base; 
         FIG. 14  is an exploded perspective view of the reverse osmosis water filtration cartridge; 
         FIG. 14A  is an enlarged perspective view of a plunger or float, including a frusto-conical nose having a channel therein for bleeding brine water when in a nested or seated position within the flush-flow activation chamber; 
         FIG. 15  is a top planar view of the base unit, illustrating various couplers in the base unit; 
         FIG. 16  is a cross-sectional view of the reverse osmosis water filtration cartridge taken about the line  16 - 16  in  FIG. 5 , illustrating one embodiment of a flush-flow activation chamber having a plunger in a seated position substantially occluding brine water outflow; 
         FIG. 17  is an alternative cross-sectional view similar to  FIG. 16 , illustrating movement of the flush-flow plunger from an engaged position to a disengaged position substantially permitting brine water outflow; 
         FIG. 18  is an alternative cross-sectional view similar to  FIGS. 16 and 17 , further illustrating movement of the flush-flow plunger from the disengaged position to reengage the seated position again occluding brine water outflow; 
         FIG. 19  is a cross-sectional view similar to  FIG. 16 , illustrating an alternative plunger for use with the flush flow activation chamber disclosed herein; 
         FIG. 20  is a cross-sectional view similar to  FIG. 19 , illustrating movement of the alternative plunger from a disengaged position to an engaged position; and 
         FIG. 21  is a cross-sectional view of the particulate catalyst post-membrane filtration cartridge taken about the line  21 - 21  in  FIG. 5 , illustrating disruption of the particulate catalyst material therein when refreshed by the flush-flow activation chamber. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the exemplary drawings for purposes of illustration, an improved water purification system is referred to generally by the reference numeral  10  in  FIG. 1 . In general, the water purification system  10  disclosed herein is designed to provide improved filtration characteristics of the type of filtration systems that use reverse osmosis (“RO”) membrane-based water filtration cartridges and/or catalyst-based filtration cartridges. In this respect, the water filtration system  10  includes a flush-flow activation chamber that intermittently and automatically reenergizes the RO membrane and/or particulate catalyst by facilitating periodic rapid injection of tap water inflow to wash build-up off the RO membrane, which otherwise decreases membrane performance and service life, and to agitate the particulate catalyst. More specifically, the flush-flow activation chamber, as described in detail below, generates back pressure within the filtration system  10 , the release of which results in rapid injection of tap water inflow. Rapid movement of fresh or additional tap or unfiltered water inflow into the filtration cartridges increases the velocity of water traveling over and against the RO membrane to break up build-up thereon, and increases the velocity of water travelling through the particulate catalyst further intermixing or agitating the matter to sufficiently prevent clumping or grouping of the matter that may otherwise form during periods of relatively slow tap water inflow. 
     As shown in  FIG. 1 , the water purification system  10  receives tap water inflow from a tap water supply  12  via a tap water inflow conduit  14  coupled to an input port  16  shown in  FIG. 1  protruding generally out from a rear portion of a manifold housing  18 . The water purification system  10  separates this tap water inflow, as explained in more detail below, into relatively purified water and a so-called retentate or brine flow having contaminants and impurities substantially concentrated therein. As shown in  FIG. 1 , the purified water exits the water purification system  10  through a pure water outlet port  20  for travel through a pure water conduit  22  to a faucet  24  or the like for on-demand dispensing. Alternatively, the pure water conduit  22  may be coupled to a water reservoir where pure water is stored before dispensing, as is generally known in the art. The retentate or brine water separated from the pure water during the purification process exits the water purification system  10  through a brine water outlet port  26  similarly mounted to and protruding out from a rear portion of the manifold housing  18 . The retentate or brine water is then discarded or recycled as generally identified by a brine removal box  28 . The brine water is preferably recycled to a hot water side or hot water circuit of a domestic water supply system to avoid water waste in accordance with the embodiments shown and described in U.S. Pat. No. 8,298,420, the contents of which are herein incorporated by reference. 
     Alternatively, and certainly less preferably, the retentate or brine water may simply be disposed from the system via a drain. 
     The water purification system  10  is designed to provide a ready supply of substantially purified water for drinking, cooking, etc. through the faucet  24  or other comparable device that preferably utilizes or preferably requires substantially pure water (e.g., an ice maker). The system  10  is generally designed for residential or household use, or for use in a commercial facility particularly such as an office or the like, installed typically within the compact cabinet space located beneath a kitchen-type sink or the like, with the pure water dispense faucet  24  normally mounted externally thereof such as on a countertop or adjacent sink for on-demand pure water dispensing. In one embodiment, the pure water dispense faucet  24  may be installed alongside or in close proximity with a conventional faucet or faucet set including cold and hot water faucet valves operable for respectively dispensing of untreated cold water and untreated hot water, or a temperate mixture thereof, through one or more dispense spouts, as shown in the U.S. Pat. No. 8,298,420. 
     In another embodiment, as part of brine removal  28 , the brine water outflow may connect to a standard domestic water supply system (not shown) having a tap water supply coupled to a cold water circuit and related cold water faucet, and a hot water circuit and related hot water faucet. Persons skilled in the art will recognize that single-handle faucet sets can be used for dispensing cold water, hot water, or a tempered mixture thereof. The brine water removed via the water purification system  10  may be utilized or connected to one or both of the cold water or hot water taps for dispensing during normal water usage, such as for purposes of washing or bathing, i.e., uses that otherwise do not require substantially purified water, such as may be desired for consumption (e.g., drinking water or purified ice cubes). 
     During normal operation, the tap water inflow passes through the water purification system  10  for treatment by a multi-cartridge filtration unit  30  that preferably includes a trio of cartridges such as a reverse osmosis (RO) water filtration cartridge  32 , a pre-filtration cartridge  34  and/or a post-filtration cartridge  36 . Persons of ordinary skill in the art will readily recognize that various combinations and quantities of filtration cartridges may be used with the water purification  10  disclosed herein based on the desired filtration requirements. Preferably, the water filtration system  10  includes at least one RO cartridge  32  having an RO membrane  38  ( FIGS. 8 and 13-14 ) therein for separating the tap water inflow into a relatively purified water supply and brine water. The pure water may be stored in a reservoir, as shown in detail in U.S. Pat. No. 8,298,420, or produced on-the-fly to facilitate on-demand dispensing through the faucet  24  or the like. Simultaneously, brine water is preferably recycled to a hot water side of a domestic water system, as may be generally referenced herein at the brine removal box  28 . Persons of ordinary skill in the art will recognize that there may be different mechanisms for providing on-demand or substantially on-demand delivery of purified water flow for consumer use, and that there may be a variety of compatible mechanisms for recycling or disposing the brine water. 
     Persons skilled in the art will also recognize and appreciate that the purified water has impurities substantially removed therefrom, whereas these removed impurities are retained within and carried off by the retentate or brine flow for recycling to the water supply system in the preferred embodiment. 
     This retentate or brine water may, alternatively, be dispensed by other means, including to a drain. While the term brine is commonly used to refer to this retentate flow, persons skilled in the art will understand that the level of impurities carried by this brine flow does not render the water toxic or harmful for a wide range of traditional domestic water supply uses such as washing, bathing, etc. Indeed, when this retentate or brine water intermixes with other water within the water supply system, the proportional increase in overall impurities is virtually unnoticeable. 
       FIGS. 2-5  more specifically illustrate the water purification system  10  for use in association with a removable and replaceable multi-cartridge filtration unit  30 . Specifically,  FIG. 2  illustrates the water purification system  10  including the outer housing or manifold cover  18  having a slidable or a movable drawer  40  ( FIG. 3 ) therein with a front margin that includes a closure panel  42 . An externally accessible drawer pull  44  formed from a portion of the closure panel  42  facilitates manual movement of the drawer  40  between an open position (e.g.,  FIGS. 3-4 ) with a portion of the drawer  40  exposed at a front end of the water purification system  10 , and a closed position (e.g.,  FIGS. 2 and 5 ). The water purification system  10  further includes a clearance ramp  46  positioned below the closure panel  42  to facilitate alignment when sliding the drawer  40  from the open position to the closed position. For example, the weight of the multi-cartridge filtration unit  30  may cause a bottom leading edge  48  of the closure panel  42  to deflect downwardly when the slidable drawer  40  is in the open position shown in  FIGS. 3-4 . Accordingly, sliding the drawer  40  to the closed position shown in  FIGS. 2 and 5  allows this edge  48  to slide traverse upwardly along the inclined surface of the ramp  46  to position the closure panel  42  into the substantially closed, locked and aligned position shown best in  FIG. 2 . 
     The water purification system  10  further includes an internal base  50 , shown best in  FIGS. 3-5 , preferably generally encased or shielded from the external environment by the manifold housing  18 . In this respect, the system  10  includes a pair of side panels  52  (e.g., one shown in  FIG. 2 ) that attach to each respective portion of the manifold housing  18  about a substantially horizontal top panel  54 . The side panels  52  may include a flanged rear portion extending substantially the vertical height of the manifold housing  18  and may include a series of screw holes, connectors or the like to permit attachment to a rear panel  56  ( FIG. 2 ) in a manner similar to well-known mechanisms for securing side panels to computer cases. When assembled, the closure panel  42 , the side panels  52 , the top panel  54  and the back panel  56  substantially enclose and protect the operational aspects of the water purification system  10 , such as the multi-cartridge filtration unit  30  and related filtration cartridges  32 ,  34 ,  36  and a fixed manifold  58  mounted generally at an inboard end of the back panel  56 . 
     The internal base  50  has a set of horizontal telescoping slides coupled thereto that include a first base slide  60  positioned substantially underneath the slidable drawer  40  and a pair of sidewall slides  62  that respectively attached to inside portions of a pair of upstanding wall segments  64 . The base slide  60  provides support for the drawer  40  while the sidewall slides  62  stabilize side-to-side movement and are adapted to permit sliding movement of the drawer  40  between the open/extended and closed/retracted positions within the manifold housing  18 . As best shown in  FIG. 3 , the drawer  40  generally forms into an upwardly open pocket  66  configured for drop-in reception of a manifold base  68  of the multi-cartridge filtration unit  30 . The drawer pocket  66  includes a series of irregular surfaces such as the illustrative triangular extensions  70  formed at longitudinally off-center positions along the drawer length for mated reception into a set of corresponding notches  72  formed in the manifold base  68  of the multi-cartridge filtration unit  30 . In a particularly preferred embodiment, the slidable drawer  40  includes a pair of triangular extensions  70  formed on one side, e.g., as shown in  FIG. 3 , and a single triangular extension  70 ′ formed on an opposite side. These extensions  70 ,  70 ′ mate with respective notches  72 ,  72 ′ ( FIGS. 8 and 9 ). This keyed system between the slidable drawer  40  and the manifold base  68  ensures unidirectional or one-way drop-in reception of the multi-cartridge filtration unit  30  because the pair of notches  72  are configured only to receive the respective pair of triangular extensions  70 , while the lone notch  72 ′ on the opposite side (shown in  FIG. 10 ) is configured only to receive the lone triangular extension  70 ′ ( FIG. 3 ). 
     The multi-cartridge unit  30  may include a mechanism to facilitate transportation of the trio of cartridges  32 ,  34 ,  36 , which are preferably preassembled on the manifold base  68  before placement into the open pocket  66 . In the embodiment shown in  FIGS. 3-5 , a handle  74  is shown formed from or otherwise attached to the post-filtration cartridge  36 . In this embodiment, the handle  74  is made from a flexible reinforced polyester or comparable fabric material (e.g., canvas) extending a sufficient distance above the top of cartridge  36  to permit manual grasping or handling. Preferably the fabric-based handle  74  is collapsible upon release to occupy minimal space within the manifold housing  18 , thus maximizing the usable heights of cartridges  32 ,  34 ,  36  and further enhancing the service life of the multi-cartridge unit  30 . In this respect, the handle  74  is of a size and shape that permits easy manual grasping and manipulation of the multi-cartridge unit  30  for quick and easy drop-fit installation into or lift-out removal from the manifold housing  18 . Alternative embodiments of the handle  74  may include a single handle that interconnects one or more of the cartridges  32 ,  34 ,  36 , or multiple independent handles attached to one or more of the cartridges  32 ,  34 ,  36 . In the former embodiment, the handle conveniently interconnects the upper ends of one or more of the three cartridges  32 ,  34 ,  36 . 
     Once the multi-cartridge unit  30  seats into the slidable drawer  40  as shown in  FIG. 4 , the drawer  40  is closed by placing a force against the closure panel  42  along the directional arrow shown therein. The drawer  40  slides inwardly as the telescoping slides  60 ,  62  collapse on themselves to reposition and close the drawer  40  within the manifold housing  18 . The manifold base  68  is configured to define a predetermined sequential flow path of water through the cartridges  32 ,  34 ,  36  for optimal filtration of undesirable particulates from the tap water supply  12  when engaged with the fixed manifold  58 . In this regard, the manifold base  68  includes a ported end plate  76  configured for slide-fit connection with a complementary mounting plate  78  coupled to the fixed manifold  58 . The mounting plate  78  includes a pair of stationary cylindrical alignment pins  80  and a set of cylindrical water conduit members, including a tap water inflow coupler  82 , a pure water outflow coupler  84  and a brine water outflow coupler  86 . As shown in  FIGS. 3 and 4 , the alignment pins  80  and each of the couplers  82 ,  84 ,  86  extend or protrude outwardly from the mounting plate  78  of the fixed manifold  58  and are configured for slide-fit engagement with the ported end plate  76 . 
     Closing the slidable drawer  40  to the position shown in  FIG. 2  engages the ported end plate  76  with the fixed manifold  58  in fluid-coupled relation. The alignment pins  80  are designed to engage reciprocal bores (not numbered) in the end plate  76  to correctly align the manifold base  68  with the fixed manifold  58  such that engagement between the ported end plate  76  and the couplers  82 ,  84 ,  86  automatically functions to provide the correct fluid flow paths for proper operation of the water purification system  10 . Persons skilled in the art may recognize that other alignment mechanisms or couplers may be used in place of or in addition to the alignment pins  80  or in place of or in addition to couplers  82 ,  84 ,  86 . 
     Each of the couplers  82 ,  84 ,  86  extend out from the fixed manifold  58  to engage complementary ports  88  ( FIG. 6 ) formed in the end plate  76 . The couplers  82 ,  84 ,  86  and the end plate ports  88  include a check valve  90  spring-loaded to a normally closed position to prevent water leakage therefrom. Each check valve  90  is adapted for push-fit engagement and partial retraction by a probe  92 . The couplers  82 ,  84 ,  86  carry one or more seal rings  94  that provide slidably sealed engagement with the end plate ports  88  prior to opening movement of the associated check valve  90 . Similarly, each coupler  82 ,  84 ,  86  is mounted on the fixed manifold  58  for accommodating a short axial retraction stroke of the associated probe  92  upon registration with the check valve  90  of the associated end plate port  88 , for displacing a second, normally closed spring-loaded check valve  96  (within the fixed manifold  58 ) to an open position. Accordingly, slide-fit coupling of the end plate ports  88  with the couplers  82 ,  84 ,  86  is accompanied by opening the check valves  90 ,  96  to permit water flow, whereas slide-out separation is accompanied by spring-loaded re-closure of the check valves  90 ,  96  to prevent water leakage.  FIG. 7  is a cross-sectional view illustrating the multi-cartridge filtration unit  30  installed within the slidable drawer  40 , with the drawer  40  advanced to the closed position for assembling the ported end plate  76  in flow-coupled relation with the coupler  82  of the fixed manifold  58 . Couplers  84 ,  86 , while not shown in the cross-sectional view of  FIG. 7  couple to the ported end plate  76  in a similar manner. 
     With the multi-cartridge unit  30  installed into the manifold housing  18  and the manifold base  68  in flow-coupled relation with the fixed manifold  58 , production of pure water proceeds in a normal manner. In this regard, as shown in the schematic diagram in  FIG. 8 , the fixed manifold  58  receives tap water inflow from the tap water supply  12  via the tap water inflow conduit  14  (see also  FIG. 1 ) and the related inlet port  16 . The fixed manifold  58  includes a flow path  98  therein that delivers the tap water inflow to the manifold base  68  when the aforementioned probe  92  engages the check valves  90 ,  96  to provide fluid-coupling therebetween via the tap water inflow coupler  82  ( FIGS. 3-4 ). 
     This tap water inflow then travels through a flow path  100  to the pre-membrane filter cartridge  34  via a pre-membrane inlet port  102 . In the preferred form, the pre-membrane filter cartridge  34  may include a conventional carbon filter  104  having filtration media for capturing contaminants that may be present in the tap water inflow. From there, the pre-filtered water exits the pre-membrane filter cartridge  34  via a pre-membrane outlet port  106  and the manifold base  68  routes the filtered water flow via a flow path  108  to an RO inlet port  110  for supplying the filtered water flow to the RO cartridge  32  having a conventional semi-permeable RO membrane  38  therein. During pure water production, the RO membrane  38  separates the water inflow into two water outflows, namely relatively purified water that exits the RO cartridge  32  through a purified water outflow port  112  coupled to a flow path  114  leading to the post-cartridge  36 , and brine water that exits the RO cartridge  32  through a brine water outlet port  116  coupled to a flow path  118  leading back to the fixed manifold  58  for eventual use or disposal. 
     In the preferred embodiment disclosed herein, the produced relatively purified water exiting the RO cartridge  32  via the purified water outlet port  112  travels next to the post-filtration cartridge  36  through the manifold base  68  via the flow path  114 . Here, the purified water enters the post-membrane cartridge  36  through a post-filtration inlet port  120 . The post-membrane cartridge  36  may also include a conventional carbon-based filtration media such as a particulate catalyst  122  for capturing and removing residual contaminants from the pure water flow. From this post-membrane filter cartridge  36 , the purified water exits through a post-membrane outlet port  124  into a flow path  126  in the manifold base  68 . This substantially purified water flow in the flow path  126  exits the manifold base  68  through the pure water outflow coupler  84  in parallel with the brine water outflow exiting the manifold base  68  through the brine water outflow coupler  86  via the flow path  118 . The fixed manifold  58 , in turn, defines internal flow paths  128  and  129  for coupling the filtered pure water and the brine water respectively to a control valve  130 . 
     The control valve  130  is preferably mounted on the fixed manifold  58  within the housing  18  and able to regulate the production of pure water in accordance with the embodiments disclosed herein. For example, the control valve  130  may include any of the control valves disclosed in the U.S. Pat. No. 8,298,420. These valves may be particularly preferred in the event the system  10  is used in connection with a storage reservoir. Additionally, the control valve  130  also preferably regulates whether the brine flow is recycled back into the water system for use in cleaning or bathing, or whether the brine water is discarded to a drain. 
       FIGS. 9-21  more specifically illustrate the details and operational aspects of the cartridges  32 ,  34 ,  36  in connection with an automatic flush-flow activation chamber that intermittently and automatically self-cleans the RO membrane  38  and reenergizes filter particulate and the like to significantly extend the operational service life of the multi-cartridge unit  30  by several years over known products. Additionally, the flush-flow activation chamber enhances the quality of water purification in the water purification system  10  because the RO membrane  38 , particulate matter or other water purification devices remain substantially clean and energized while in service. 
     For instance, with respect to the embodiments disclosed above,  FIGS. 9 and 10  more specifically illustrate the manifold base  68  having a set of threaded cartridge carriers, including an RO cartridge carrier  132 , a pre-membrane cartridge carrier  134  and a post-membrane cartridge carrier  136 . 
     As shown, each of the cartridge carriers  132 ,  134 ,  136  include internal threads  138  configured to rotatably engage through threaded reception of a set of exterior threads  140  formed along an exterior surface of a corresponding set of carrier cartridge housings  142 . Threaded engagement of the cartridge housings  142  to the carrier cartridges  132 ,  134 ,  136  produces an air and water-tight seal to prevent leakage during normal operation of the water purification system  10 . In this respect, in one embodiment, the threads may include a sealant to prevent such leakage. Although, it is preferred that the threads  138  and  140  provide sealing engagement without the use of a sealant or other chemical therein. During non-use and when the multi-cartridge unit  30  is no longer in the manifold housing  18 , such as during service or replacement, the carrier cartridge housings  142  may be unscrewed from their respective cartridge carriers  132 ,  134 ,  136  to gain access to the water filtration equipment inside. Thus, the multi-cartridge unit  30  can be removed out from within the manifold housing  18  and returned to the manufacturer to have the RO membrane, carbon-based particulate matter or the carbon-based filter element removed and replaced or recharged. This way, the manifold base  68  can be reused when the old filtration media is removed or needs replacing. 
       FIG. 10  more specifically illustrates the flow paths in the manifold base  68  that channel tap water, pure water and/or brine water in and among the various cartridge carriers  132 ,  134 ,  136 . For instance, in view of the diagrammatic view of  FIG. 8 , tap water inflow that enters the manifold base  68  through the tap water inflow coupler  82  travels to the pre-membrane filtration cartridge  34  via the flow path  100 . In  FIG. 10 , the pre-membrane inlet port  102  is shown in the base of the pre-membrane cartridge carrier  134 . In this embodiment, the tap water inflow is initially filtered through the pre-membrane cartridge  34 , such as the carbon filter  104  shown in  FIGS. 11-13 . The carbon filter  104  includes a cartridge carrier coupler  144  ( FIG. 11 ) generally extending out from a lower base of the cartridge unit that selectively slidably engages the pre-membrane outlet port  106  ( FIG. 10 ). This cartridge carrier coupler  144  includes a pair of o-rings  146 ,  146 ′ preferably made from a somewhat deformable material such as rubber to ensure an air-tight and water tight seal between the cartridge carrier coupler  144  and the pre-membrane outlet port  106 . This seal prevents filtered water from intermixing with the tap water inflow entering the pre-membrane filtration cartridge  34 . In this respect, tap water inflow entering the pre-membrane cartridge  34  through the pre-membrane inlet port  102  surrounds the carbon filter  104  within a chamber formed by a gap or space  148  ( FIG. 13 ) between the exterior surface of the carbon filter  104  and the interior surface of the carrier cartridge housing  142 . 
     In this embodiment, the carbon filter  104  includes a solid interior carbon-based filter media  150  surrounded by an exterior sheath  152  compressed or held tightly to the outside of the media  150  by a somewhat stretchable or elastic netting  154  made from plastic or a comparable polymer. The solid carbon media  150  filters the tap water supply by suspending impurities as the fluid makes its way through the filter media  150  and into a central tube  156  coupled to the pre-membrane outlet port  106 . The filter media  150  helps remove debris and particles from the tap water inflow that could damage the RO membrane  38 . Furthermore, removing such impurities helps avoid clogging that might decrease the effectiveness of other water filtration equipment in the system  10 . 
     This filtered tap water flow then travels out from the pre-membrane cartridge  34  via the pre-membrane outlet port  106  and into the flow path  108  ( FIGS. 8 and 13 ), which couples to the RO inlet port  110  of the RO water filtration cartridge  32  ( FIG. 13 ). The RO inlet port  110  permits the filtered tap water to enter into an entry channel  158  formed from a portion of the RO cartridge carrier  132  as shown in  FIGS. 11 and 13 . Here, the filtered tap water may enter a base unit  160  ( FIGS. 13-14 ) at a lower section  162  thereof, which includes a pair of o-rings  164 ,  164 ′ that selectively slidably engage an upstanding shoulder or wall  166  formed within the interior of the RO cartridge carrier  132  to form an air-tight and water-tight seal therebetween. The base unit  160  further includes an upper end  168  having a diameter relatively larger than the lower end  162  and sized to carry a pair of o-rings  170 ,  170 ′ that selectively slidably engage the interior surface of the carrier cartridge housing  142  to form an air-tight and water-tight seal therebetween. This permits the RO water filtration cartridge  32  to separate the filtered tap water flow into a relatively pure water flow for delivery to a dispense faucet for consumption or cooking purposes and a brine water flow to be recycled into the tap water flow for use in washing or bathing, or to be discarded to a drain, as discussed below in more detail. 
     When the lower end  162  of the base unit  160  is in seated reception within the wall  166  of the RO cartridge carrier  132 , filtered tap water entering through the RO inlet port  110  flows into and fills the channel  158  below an aperture  172  that permits the filtered water flow to enter a space or region  174  ( FIG. 13 ) immediately below an RO filter  176 . As shown in  FIGS. 13 and 14 , the RO filter  176  couples to a filter port  180  through slide-in reception of a RO filter seal  182  having a lower section  184  and an upper section  186  that generally taper outwardly into a larger diameter point  188  that sealing engages the inner diameter or wall of the filter port  180  in the base unit  160 . A piece of tape  190  may be disposed across a portion of the upper section  186  to retain the seal  182  at a specific location along the length of the RO filter  176 . The seal  182  preferably outwardly terminates at the point  188  having an outer diameter somewhat larger than the inner diameter of the filter port  180  such that an air-tight and water-tight seal forms therebetween when the RO filter  176  engages the base unit  160 . The seal  182  should be made from a somewhat deformable or flexible material such as rubber so as to permit insertion into the filter port  180 . 
     Furthermore, the RO filter  176  includes a filter coupler  192  having a pair of o-rings  194 , 194 ′ thereon for selected air-tight and water tight-reception into a base unit outlet coupler  196  ( FIG. 15 ). This way, filtered tap water entering the base unit  160  though the aperture  172  is separately maintained within the space/region  174  ( FIG. 13 ) such that the filtered tap water must flow up into the series of membranes  178  in the RO filter  176 , thereby purifying the filtered tap water into a substantially pure water flow that concentrates in an RO discharge tube  198  before delivery back to the manifold base  68  through the filter coupler  192  and the purified water outlet port  112 . 
     Preferably, the RO filter  176  is the CSM RE1 81 2-24 Reverse Osmosis Membrane manufactured by Woongjin Chemical Company of Seoul, Korea, although persons of ordinary skill in the art may recognize that other filters known in the art may be compatible with the system  10  disclosed herein. In this respect, the RO membranes  178  preferably substantially filter out bacteria, progenies, viruses, pesticides, hydrocarbons, radioactive contaminants, turbidity, colloidal matter, chlorine, detergents, industrial wastes, asbestos, and other dissolved solids such as sodium, calcium, magnesium, sulfates and cadmium. These dissolved inorganic solids are removed from the filtered tap water by pushing the filtered tap water through the semi-permeable membranes  178 . These membranes  178 , which are about as thick as cellophane, only allow water to pass through, not the impurities or contaminants. The impurities or contaminants exit the RO filter  176  at a top end  200  thereof as brine water. 
     As shown best in  FIG. 13 , the RO discharge tube  198  includes a stop  202  that separates the clean or purified water side having a set of perforations  204  therein to permit pure water to exit the RO filter  176 , as described above, from the brine water side. Brine water outflow, as designated by numeral  206 , is allowed to exit the RO filter  176  at the top end  200  thereof because the RO filter membranes  178  remain open or exposed due to offset engagement of a standoff  208  with a complementary fitting  210  formed from a portion of a spacer or header  212 . In this respect, the standoff  208  is of a length that positions the header  212  at a predefined distance above the top end  200  of the RO filter  176  to permit the brine water outflow  206  to exit the RO filter  176  as shown in  FIG. 13 . The stop  202  prevents this brine water outflow  206  from mixing with the pure water outflow in the RO discharge tube  198 . 
     The header  212  is also designed to fill the space remaining above the RO filter  176  so the RO water filtration cartridge  32  can house RO filters that vary in size. Furthermore, the header  212  ensures that each component in the RO filtration cartridge  32  remains in adequate engagement to prevent leakage. In this respect, the header  212  includes a somewhat circular extension  214  ( FIG. 14 ) having an outside diameter approximately the same size as an inside diameter of a flexible or deformable corrugated spacer  216  ( FIGS. 11-14 ). The spacer  216  may flex about its corrugations to optimally and snugly couple to the circular extension  214  for slide-fit reception thereon, and to securely bias the filtration assembly within the interior of the carrier cartridge housing  142 . 
     Furthermore, the RO water filtration cartridge  32  further includes a flush-flow activation chamber  218  as shown in  FIGS. 11-14 and 16-20 . In the preferred embodiment, the flush flow activation chamber  218  generally includes a vertical tube  220  extending between the header  212  and the base unit  160 . The vertical tube  220  is preferably made from a single tube (as shown in the illustrative drawings), but it may also be made from multiple interconnecting tubes, depending on the desired length. The vertical tube  220  attaches the flush-flow activation chamber  218  between the header  212  and the base unit  160  as shown. The tube  220  is configured to carry, in one embodiment, a water weight or plunger  222 . As shown best in  FIG. 14 , the vertical tube  220  engages the outer prongs of an X-shaped extension  224  protruding out from the header  212 . The X-shaped extension  224  includes a ledge or shelf  226  extending outwardly to increase the width of the extension to prevent the tube  220  from sitting flush against a bottom surface  228  ( FIG. 13 ) of the header  212 . That is, the vertical tube  220  selectively slides over and engages the X-shaped extension  224  only to the point where the outer walls of the vertical tube  220  engage the shelf  226 —this permits inflow of brine water exiting the RO filter  176  into the vertical tube  220 . On an opposite end, the vertical tube  220  slidably engages a substantially circular drain tube coupler  230 . 
     As shown in  FIGS. 13 and 14 , the drain tube coupler  230  extends downwardly into the base unit  160  and includes an exit aperture  232  that extends through the width of the base unit housing and opens into a channel  234  between the o-rings  170 ,  170 ′. When the base unit  160  is selectively slidably retained within the carrier cartridge housing  142 , the channel  234  becomes substantially aligned with one or more exit ports  236  bored in the side of the carrier cartridge housing  142  between the o-rings  170 ,  170 ′. The channel  234  permits the brine water outflow to travel circumferentially around the exterior of the carrier cartridge housing  142  until the water can escape therefrom through one of the exit ports  236 . These exit ports  236  similarly open to a dispense channel formed from the outer diameter of the carrier cartridge housing  142 , which fluidly couples to the brine water outflow port  116  in the manifold housing  68 . Thus, brine water flow exiting the RO filter  176  enters the vertical tube  220  of the flush flow mechanism  218  through the gap formed as a result of offset seated reception of the vertical tube  220  on the shelf  226  of the X-shaped extension  224  protruding out from underneath the bottom surface  228  of the header  212  and out through the brine water outlet port  116  via the drain tube coupler  230 . 
     The operation of the flush-flow activation chamber  218  is shown in more detail in  FIGS. 14 and 16-20 . More specifically, the interior of the vertical tube  220  is of a diameter that permits vertical movement of the plunger  222  therein, namely in and among the positions generally shown in  FIGS. 16-20 . 
     The plunger  222  is designed to create a flush flow state or flushing condition that essentially refreshes or reenergizes the filtration equipment, and namely the membranes  178  in the RO filtration cartridge  30  and/or other particulate catalyst material that may be utilized by the system  10  for purposes of water filtration. In a relatively static state, i.e., when the system  10  is not dispensing water out through the faucet  24  or otherwise filling a reservoir (if one is being utilized), the plunger  222  is generally in the position shown in  FIG. 16 . Here, pressurization within the system  10  during this static state allows the weighted plunger  222  to sink to the bottom of the brine water filled vertical tube  220  for placement or engagement with a seat  240  sitting or preferably affixed to a ledge  242  formed from a portion of the interior diameter of the drain tube coupler  230 . This seat  240  has an aperture  244  therein that permits brine water outflow, but may be substantially occluded by the plunger  222  when in the position shown in  FIG. 16 . In this respect, the plunger  222  preferably includes a nozzle or nose  246  that generally tapers inwardly from a substantially cylindrical body portion  248 , as best shown in  FIG. 14A . While the cylindrical body portion  248  is larger in diameter than the aperture  244 , the nose portion  246  preferably tapers to a diameter somewhat smaller than the aperture  244  to permit a portion of the nose  246  to slide into and partially penetrate through the aperture  244 , thereby substantially occluding brine water flow therethrough. 
     When in the seated position shown in  FIG. 16 , the system  10  is in a relatively static state wherein pure water production has ceased, such as when the faucet  24  is closed or when the pure water reservoir or storage vessel shown and described in U.S. Pat. No. 8,298,420 is full. Despite being in a relatively static state, the nose  246  may still permit brine water outflow through the aperture  244  by means of a narrow slot  250  formed as a channel or conduit along the narrowing or tapered portion of the nose  246 , as shown best in  FIG. 14A . The slot  250  permits metered brine water outflow during this relative static state to prevent the system  10  from becoming completely stagnant after extended durations of no water flow. The plunger  222  essentially functions as a flow limiter to prevent substantial outflow of brine water, which beneficially reduces water waste during times of non-use. Of course, a person of ordinary skill in the art will readily recognize that the flush-flow activation chamber  218  will also work with a plunger that excludes the slot  250 . In this embodiment, and when the system  10  reaches the substantially static state described above, the plunger fully engages the seat  240  such that the nose  246  preferably entirely occludes flow through the aperture  244 , thereby ceasing all water flow out through brine water outlet port  26 . 
     Opening the faucet  24  to dispense pure water causes the system  10  to reengage in the production of pure water—either to meet on-demand dispensing needs or to refill the reservoir (if one is used). In this condition, the RO filtration cartridge  32  experiences a pressure drop as a result of the increased velocity of water traveling therethrough. That is, dispensing pure water from the faucet  24  creates a vacuum immediately therebehind, which allows pressurized tap water to inflow into the system  10  to reengage in pure water production. The plunger  222  will remain in seated engagement with the seat  240  until the back pressure at the top of the vertical tube  220  draws the plunger  222  out from engagement therewith. For this to happen, the pressure drop behind the plunger  222  must decrease to some threshold level that draws the weighted plunger  222  out from said seated engagement. A person of ordinary skill in the art will appreciate that there will be some delay between the time when pure water production is reinitialized by opening the faucet  24  and the time when the plunger  222  disengages the seat  240 . To this extent, the system  10  experiences an increasing back pressure near the top end  200  of the RO filter  176 , and especially in and around the area where the vertical tube  220  engages the X-shaped extension  224 . When this “vacuum” exceeds the weighted force keeping the plunger  222  engaged with the seat  240 , the plunger  222  pulls or pops out from within the aperture  244 . 
     Here, the water purification system  10  experiences a short, yet noticeable change in water pressure that reverberates throughout the flow paths in the fixed manifold  58  and the manifold base  68 , and especially through RO filtration cartridge  32 , the pre-membrane cartridge  34  and the post-membrane cartridge  36 . More specifically in this respect, the system  10  experiences a rush of water out from the vertical tube  220  through the now open aperture  244 , thereby creating a vacuum (i.e., decreased pressure) therebehind as a result of increased fluid flow velocity. This vacuum consequently results in a sudden increase or flash flush of tap water inflow in through the tap water inlet port  16 . This so-called flush flow has the effect of flashing an increased flow of tap or filtered water over the RO filter membranes  178  to effectively dislodge or remove contaminant particulate matter that may have accumulated thereon. In a sense, the flush-flow activation chamber  218  is a built-in self-cleaning device that clears the RO filter membranes  178  of build-up that otherwise may damage the membranes  178  and shorten its service life. 
     While pure water is being produced, the plunger  222  remains near the top of the vertical tube  220  as shown in  FIG. 17  so that brine water outflow may exit the RO filtration cartridge  32 , as described above. When pure water dispensing ceases, either by turning off the faucet  24  or by substantially filling the reservoir or storage vessel (if used), pure water production through the RO filter  176  decreases, thereby allowing the plunger  222  to sink back down toward engagement with the seat  240  as shown in  FIG. 18 . So, during non-operation, i.e., when pure water is not being dispensed from the faucet  24  or otherwise filing the reservoir or storage vessel, the desired rate of brine water production through the flush-flow activation chamber  218  is reduced to a minimal amount, i.e., the volume of water through the slot  250 , if one is used. 
     In this respect, the plunger  222  preferably falls back down to the position shown in  FIGS. 16 and 18  such that the nozzle or nose  246  repositions itself back within the aperture  244  whereby brine water outflow exits the vertical tube  220  only through the channel or slot  250 . The flush-flow activation chamber  218  then reactivates the next time the faucet  24  is opened. 
     The characteristics of the vertical tube  220  and the plunger  222  govern the speed, force and duration of the flush-flow activation chamber  218 . 
     For example, in the embodiment shown in  FIGS. 16-18 , the plunger  222  generally includes a cylindrical body portion  248  having a tapered frusto-conically shaped nose  246  that includes an angled channel or slot  250  therein that permits a relatively low volume of brine water to flow through the aperture  244  at times of little or no pure water production. Furthermore, the outer diameter of the cylindrical body portion  248  is slightly smaller in diameter relative to the inner diameter of the vertical tube  220 . This permits some fluid flow through and around the plunger  222  and has a tendency to require a higher vacuum within the system  10  to dislodge the plunger  222  from the seat  240  than an embodiment wherein the vertical tube  220  has an inner diameter appreciably larger than the outer diameter of the plunger. Although, conversely, the smooth outer diameter of the cylindrical body portion  248  does reduce turbulence along the surface of the plunger  222 , thereby relatively reducing the needed back pressure to dislodge the plunger  222  from the seat  240 . For example, the plunger  222  may be dislodged from the seat  240  with relatively less force than plunger  222 ′ ( FIGS. 19-20 ), thereby creating a relatively lower flushing force across the membranes  178  and other filtration equipment. 
     The flush-flow activation chamber  218  may also be changed in numerous other ways to regulate the rate of resetting the flush-flow mechanism, and the speed and force of the flush-flow when the mechanism activates. For example, lengthening the vertical tube  220  will increase the time it takes the plunger  222  to reseat after the active water purification state, thus decreasing the intervals between flush-flows. The same is true in the inverse, i.e., when more frequent flush flows are desired, the system  10  could include a shorter vertical tube  220 . Alternatively, a plunger having an outside diameter approximately the same size of the inside diameter of the vertical tube  220  requires greater pressure therein for removal from the seat  240  because of less fluid flow characteristics in and around the plunger  222 , thereby increasing the force of the flush-flow when the plunger does release. The alternative is, of course, that a relatively larger inside diameter vertical tube  220  and/or a relatively smaller outer diameter plunger will require less force for removal and generate less flush-flow force across the system  10 . 
     Of course, the flow characteristics inside the vertical tube  220  could be governed by other features. For example, in one embodiment as shown in  FIGS. 19-20 , an alternative plunger  222 ′ may have a set of fins  252  that extend outwardly from the cylindrical body thereof to more closely track the internal diameter of the vertical tube  220 . In this embodiment, the plunger  222 ′ will tend to resist fluid flow around its body, especially by decreasing the flow characteristics in and around the fins  252 . Such increased turbulence tends to resist movement, as opposed to laminar flow that may be more readily experienced with the smoother cylindrical body portion  248 , within the vertical tube  220 . As a result, the system  10  must produce a higher force to dislodge the plunger  222 ′ from the seat  240 , which results in a larger flush-flow across the RO membranes  178  and other filtration equipment. Of course, a person of ordinary skill in the art will readily recognize that other modifications may be made to the size and shape of the vertical tube  220  and to the plunger  222  to regulate the rate the plunger  222  disengages or reengages the seat  240  in accordance with the embodiments described herein. 
     For example, in another embodiment, the weight of the plunger  222  has bearing on the operation on flush-flow activation. More specifically, in one embodiment where the plunger is used as a sink, increasing the weight of the plunger will increase the rate at which the plunger returns to the seat  240 . 
     The same is true in the inverse, namely decreasing the weight of the plunger increases the rate at which it raises within the vertical tube  220  and decreases the rate it falls when the system back pressure is removed. In this case, the flush-flow activation occurs less frequently due to the relatively longer time it takes the plunger to reseat. In another alternative, a float may be used instead of a weighted plunger. In this respect, instead of sinking, the float is buoyant within the vertical tube  220  and tends to rise therein for engagement with the seat  240  during times of non-use or relatively slow pure water production, the float then is pulled downwardly by the vacuum back pressure when the faucet  24 , for example, is opened such that the system  10  experiences higher velocity inflow to produce on-demand purified water for consumption. Here, increasing the buoyancy of the float increases the rate it returns to the seated position, and vice versa. 
     As described above, pure water produced by the RO filtration cartridge  32  exits through the purified water outlet port  112  and travels through the flow path  114  ( FIG. 8 ) to the post-membrane cartridge  36 . This post-membrane cartridge  36 , as shown in  FIGS. 11-13 and 21 , includes the post filtration inlet port  120  for receiving this pure water inflow from the RO water filtration cartridge  32 . This purified water enters the post-membrane cartridge  36  through the post filtration inlet port  120  into a space or chamber  254  ( FIGS. 13 and 21 ) formed beneath a lower catalyst filter element  256 . A set of flow apertures  258  are covered by a filter or screen  260  to the inboard side relative to the purified water inflow. The screens  260  permit purified water inflow, while preventing the relatively larger particle particulate catalyst media  262  from back flowing out the flow apertures  258 . An upper catalyst filter element  264  has a similar filter or screen  266  to permit purified water outflow from a catalyst cleansing chamber, formed generally between these two filter elements  256 , 266 , and into a headspace  268 . The catalyst cleansing chamber is at least partially filled (preferably less than ½ the chamber volume) with particulate catalyst media or agent  262  such as zinc, a copper-zinc catalyst mixture, or the like. A portion of the catalyst zinc dissolves into the pure water flow passing therethrough, for purposes of maintaining water and storage tank freshness. Purified and enriched water exits the catalyst cleansing chamber through the screen  266  and into the headspace  268  for eventual travel out through a hollow central stem  270  having a crowned head  272 . The purified water discharges the post-membrane cartridge  36  through the post-membrane outlet  124  for travel in the flow path  126  to the control valve  130  and for eventual dispensing out through the faucet  24 . 
     The particulate catalyst media  262  within the post-membrane cartridge  36  is periodically refreshed by the flush-flow activation chamber  218  to achieve extended service life compatible with the extended service life of the RO membrane  38 . For example, fluid flow within the system  10  slows significantly when the faucet  24  is turned “off” and/or when the reservoir is fills (if used). At this stage, pure water production slows and brine water discharge slows to a drip through the aforementioned slot  250 . Particulate catalyst media  262  known in the art has a tendency to clump together during relatively slow tap water inflow and related pure water production. As such, the particulate catalyst media  262  forms channels therein that can significantly decrease filtration performance over time because a relatively small amount of catalyzing material remains exposed to water traveling through the post-membrane cartridge  36 . When the flush-flow mechanism described above activates, it causes a sudden increase in the velocity of water travelling into the cartridge through the post-filtration inlet port  120 . This water rushes into the catalyst cleansing chamber resulting in stirring and fluidizing of the media  262  (e.g., as shown in  FIG. 21  relative to  FIG. 13 ) sufficient to turbulently abrade and refresh the media  262 . This feature of the system  10  further extends the operational service life of the media  262  as it intermittently breaks apart and refreshes the particulate catalyst media  262 . 
     Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.