Abstract:
A liquid chemical dispenser for an irrigation system comprises a removable supply container for the chemical which, in a first embodiment, comprises a valve for preventing spillage of the chemical during attachment of the container to the dispenser. This feature allows the container to be mounted in an inverted position on the dispenser without loss of its contents. In a second embodiment, the chemical container comprises a membrane which is pierced by a dip tube when the container is attached to the dispenser. A section of the dip tube produces an annular vent passage in the membrane around the dip tube to provide vacuum relief. The configuration of the containers substantially reduces the chance of inadvertent contact with the contents and the simple design permits the containers to be disposable.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of co-pending U.S. patent application Ser. No. 11/424,773 filed Jun. 16, 2006, now issued as U.S. Pat. No. x,xxx,xxx. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to irrigation systems. More particularly, it relates to devices for adding liquid fertilizers, insecticides, herbicides, fungicides and the like to the water distributed by an automatic sprinkler system. 
         [0004]    2. Description of the Related Art 
         [0005]    The availability of low-cost PVC pipe and solvent-welded PVC pipe fittings has resulted in the widespread installation and use of automatic sprinkler systems. Such systems typically comprise a source of fresh water under pressure (often a community water utility), a manifold for distributing the water into various zones each having a plurality of sprinkler heads, a series of electrically-actuated valves for controlling the flow of water in each of the zones, a timer for opening and closing the valves at pre-selected times or time intervals, and a backflow prevention device for keeping possibly contaminated water from re-entering the supply system. 
         [0006]    An in-ground, automatic sprinkler system presents the opportunity to conveniently distribute water-soluble chemicals such as fertilizers, weed killers, fungicides, and insecticides to areas served by the system. A number of United States patents concern devices for adding water soluble chemicals to sprinkler and irrigation systems. 
         [0007]    U.S. Pat. No. 7,011,254 to Thornton describes a lawn chemical application system that comprises a dispenser having a lower chamber, an upper chamber, an upstream opening, and a downstream opening. The dispenser may be formed by a tee connector and a cylinder secured to an upper opening of the tee connector. Powered valves are operably connected to the upstream and downstream openings of the dispenser. The powered valves may be wired to open and close simultaneously. A lower portion of the upper chamber may be disposed below an upper portion of the lower chamber and above a lower portion of the lower chamber, leaving the lower portion of the lower chamber unobstructed over substantially its entire length. The lower portion of the upper chamber may have a plurality of openings to provide for adequate mixing of water with the chemicals stored in the upper chamber. In operation, soluble matter or other chemicals are placed in the upper chamber of the dispenser, and the two valves are opened simultaneously. Water flows through the first powered valve and into the dispenser, where the water is mixed with soluble matter or other chemicals stored in the upper chamber of the tee. The solution or mixture then passes from the dispenser, through the second powered valve, to one or more sprinkler heads of the irrigation system. When the application is finished, the valves are closed simultaneously. 
         [0008]    U.S. Pat. No. 6,997,350 to Johnson et al. describes an apparatus for adding liquid fertilizer to a water line of a sprinkler system. The apparatus includes a mechanical injector device powered by a paddle wheel turned by water flowing through the water line. The mechanical injector device includes a plunger that moves back and forth in the plunger chamber. Movement in one direction allows liquid fertilizer from a liquid fertilizer reservoir to flow into the plunger chamber and movement of the plunger in the opposite direction injects the liquid fertilizer from the plunger chamber into the water. The mechanical injector device is coupled to the paddle wheel which causes movement of the plunger in the plunger chamber in at least one direction. Spring bias can cause movement of the plunger in the other direction. The mechanical injector device can be disabled to stop fertilizer injection while still allowing rotation of the paddle wheel. The paddle wheel is coupled to the mechanical injector device through a plunger gear which rotates, and interacting camming surfaces which project from the plunger gear and from a ratchet. 
         [0009]    U.S. Pat. No. 6,969,011 to Palmer describes a chemical additive dispensing device for use with a station of a sprinkler-based irrigation system that includes a fluid diversion housing and a container for storing a chemical additive. The fluid diversion housing includes an in-flow channel formed therein that is in fluid communication with an input port and the container. An out-flow channel is also formed within the fluid diversion housing and is in fluid communication with an output port and the container. In operation, the container fills with fluid from the in-flow channel such that the fluid mixes with the chemical additive. Once the container is filled with fluid, the mixture of fluid and chemical additive is diverted through the out-flow channel of the fluid diversion housing to the outlet port such that the fluid chemical additive mixture is distributed to the rest of the irrigation system and particularly through sprinklers onto a lawn and/or plants. 
         [0010]    U.S. Pat. No. 6,942,128 to Walter describes an automatic dispenser for underground sprinkler-systems. The unit is placed before the zone valves of the sprinkler system. The unit is designed to disperse fertilizer into a tank chamber below a discharge tray. The fertilizer dissolves in the water and is distributed/dispersed to the appropriate sprinkler system zone. The discharge tray has multiple chambers based on the number of zones in the sprinkler system. The chambers in the discharge tray can hold various capacities based on the area covered by each zone within the sprinkler system. The discharge tray turns to dispense the fertilizer as the sprinkler system changes from zone to zone. The discharge tray is automatically moved. The chambers are manually refilled based on the frequency of yard fertilization. The unit has an access from the top to the discharge tray for filling chambers with fertilizer material. 
         [0011]    U.S. Pat. No. 6,722,583 to Restaino et al. describes a lawn sprinkler accessory with a hollow body defining a chamber for holding lawn treatment material, such as fertilizer, herbicide or insecticide. The accessory body has a hollow water inlet arm on one side and a hollow water outlet arm on the opposite side of the chamber. An access opening with a removable closure in one end of the accessory body enables the insertion of lawn treatment material into the chamber and its removal from the chamber. 
         [0012]    U.S. Pat. No. 6,540,156 to Martin describes a fertilizer and irrigation apparatus that includes an inflow pipe, a shunt pipe connected to the inflow pipe, and a chemical additive assembly connected in parallel to the shunt pipe. An outflow pipe is also connected to the shunt pipe. A portion of the inflow pipe, the shunt pipe, the chemical additive assembly, and the outflow pipe are all above ground. The chemical additive assembly includes a quantity of a chemical additive. A manifold is connected to the outflow pipe. A plurality of in-ground distribution conduits are connected to the manifold, wherein each of the distribution conduits includes at least one above-ground sprinkler head. In addition, an auxiliary inflow assembly can be connected to the inflow pipe so that chemical additives can be supplied to the fertilizer and irrigation apparatus from an outside source. 
         [0013]    U.S. Pat. No. 6,267,303 to Francis describes a sprinkler system fertilizer injector that comprises a device for injecting liquid chemical solutions into the flow of a lawn sprinkler system. The device is said to allow the user to easily attach and remove chemical jars without the risk of losing the prime on the pump. 
         [0014]    U.S. Pat. No. 6,206,046 to Finley describes a lawn and garden chemical dispensing system that employs an I.V.-style collapsible bag as a water flow controlled dispenser of liquid or water-soluble beneficial chemicals for sprinkling systems. The system consists of a stand, a chemical vessel, a vessel sleeve, a vessel cap with dual port (internal/external) bulkhead union, an optional filter attachment, a chemical feed tube, and a control valve tap connected to a water flow supply. 
         [0015]    U.S. Pat. No. 6,173,732 to Davis et al. describes a chemical feeding system for adding either liquid or 100% water soluble solid chemicals including fertilizer, insecticide and a herbicide to a lawn sprinkler system either above or below ground level. The system has one or two vertically oriented mixing chambers containing a removable sponge filter. An effluent tube is attached to the bottom of the mixing chamber for recycling through an adjustable flow meter valve. A drain tube with a shutoff valve and a one-way check valve leads to the main sprinkler system. 
         [0016]    U.S. Pat. No. 5,836,518 to Jester describes a fertilizer sprinkler system including a pipe system adapted for flow of liquid therethrough. The pipe system is comprised of an open inboard portion, a closed outboard portion and an intermediate portion. The inboard portion is coupled to a main water line. The intermediate portion is defined by a first vertical member, a horizontal member and a second vertical member. The intermediate portion further has a lower horizontal member having a first end in fluid communication with the first vertical member and a second end in fluid communication with the second vertical member. The lower horizontal member has an intermediate segment having an integral lid extending downwardly therefrom. The lid has an inlet port and an outlet port therethrough. A fertilizer container removably couples with the lid of the pipe system. A plurality of outlet valves are positioned within the outboard portion of the pipe system. The plurality of outlet valves are adapted for coupling with sprinklers. 
         [0017]    U.S. Pat. No. 5,366,159 to Childers describes an automatic fertilizing apparatus which injects fertilizer directly into the water stream of a sprinkler system. Each time the sprinkler system is activated, a predetermined amount of fertilizer is dispensed into the water stream. The apparatus can be controlled to dispense fertilizer only thru sprinkler lines determined by the user. 
         [0018]    U.S. Pat. No. 5,364,030 to Murdock et al. describes a solution injector for underground sprinkler systems comprising an intake pipe connected with a bypass pipe at a system inlet pipe “T”, a tank, and an outflow pipe connected at one end to the tank and at the other to the bypass pipe. The intake pipe is connected to the tank through an intake valve and an intake hose, and the solution injector further comprises a bypass valve installed on the bypass pipe between the system inlet pipe “T” and the system outlet pipe “T”. 
         [0019]    U.S. Pat. No. 5,303,729 to DeMarco describes An automatic fertilizing device for introducing lawn care chemicals such as fertilizer, herbicides, insecticides, and fungicides into a sprinkler system, comprising a container having a control plate insert to divide the container into an upper and lower volume. The container and control plate are mounted to a flow head, such that the flow head controls the amount of chemicals drawn from the container and dispersed into the main water line. 
         [0020]    U.S. Pat. No. 5,199,645 to Anderson et al. describes a conversion kit for converting an existing sprinkler system liquid supply line into a general purpose soluble chemical application device is used to apply insecticides or fertilizer. The easily installed kit mixes dry chemicals with an existing pressurized liquid to form and expel appropriate treatment solution. Spent dry chemicals can be easily replaced in a removable canister. Chemicals from conventional bulk packages or specially prepared packets may be used. A safety interlock shutoff valve is provided to prevent pressurization of the system while chemicals are being replaced. A vacuum breaking air vent valve is provided to allow drainage of liquid from the system. All components are enclosed within and supported by a single housing. 
         [0021]    U.S. Pat. No. 5,178,181 to Craig describes an applicator for use with a sprinkler line system. The applicator comprises a fertilizer container with integrally formed internal inlet and outlet tubes. Water is fed through an inlet-outlet tube into the bottom of the fertilizer container, where it dissolves or dilutes some of the solid or liquid fertilizer and forms a leached, concentrated solution. This concentrate continuously rises through the fertilizer and into the outlet tube where it drains downwardly. The concentrate is then diluted with water coming through the inlet-outlet tube including a venturi, the size of which controls the flow rate of the concentrate. The diluted concentrate is then passed into the sprinkler system for application to vegetation. The bore arrangement of the applicator enables the device to be drained and then filled with fertilizer, followed by running water through the fertilizer at a selected time. This is said to render the operation more automatic. 
       BRIEF SUMMARY OF THE INVENTION 
       [0022]    A dispenser for attachment to a sprinkler system is adapted to receive or connect to a disposable container filled with a water-soluble chemical or an aqueous solution. The container is designed such that the user is not exposed to the chemical or solution when attaching or removing the container from the dispenser. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0023]      FIG. 1  depicts a lawn sprinkler system equipped with a chemical dispenser according to a first embodiment of the invention. 
           [0024]      FIG. 2  illustrates a chemical dispenser according to a second embodiment of the invention installed in the supply line of an in-ground sprinkler system. 
           [0025]      FIG. 3  is a cross-sectional view of a portion of the chemical dispenser and chemical container of the system illustrated in  FIG. 1 . 
           [0026]      FIG. 4  is an enlarged cross-sectional view of the portion indicated in  FIG. 3 . 
           [0027]      FIG. 5  is a cross-sectional view taken along line  5 - 5  in  FIG. 4 . 
           [0028]      FIG. 6  is a partially cut-away, exploded view of the connector portion of the chemical dispenser illustrated in  FIGS. 1 and 3 . 
           [0029]      FIG. 7  is a cross sectional view of the chemical dispenser according to the embodiment shown in  FIG. 2 . 
           [0030]      FIG. 8  is an alternative embodiment of the portion shown in the dashed circle in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Referring to  FIG. 1 , a typical in-ground lawn sprinkler system  10  includes water line  12  for supplying fresh water from a pressurized source—e.g., a community water system, a well, a spring, surface water or the like. Backflow preventer or anti-siphon valve  14  may be included in line  12  to prevent the contamination of the water source in the event of a loss of supply pressure. The illustrated system is comprised of two zones, each comprising a branch line  22 , at least one sprinkler head  28 , and an electrically-actuated solenoid valve  24 . Electrical conductors  26  connect valves  24  to a central control station (not shown) which may comprise a timer for opening and closing selected valves  24  at pre-selected times. In operation, a selected valve  24  may be opened, causing water to flow from supply line  12 , through the branch line  22  downstream from the selected valve  24  and out onto lawn  30  by way of the sprinkler head(s)  28  connected to branch line  22 . The simplified sprinkler system  10  of  FIG. 1  comprises only two zones, each having a single sprinkler head. It will be understood by those skilled in the art that an actual sprinkler system may have any number of zones and the number of sprinkler heads per zone may be limited by the supply pressure and the size of the pipes and fittings comprising the system. The invention is not limited to use with lawn sprinkler systems, but may be used in conjunction with any irrigation system. Even residential systems may include separate zones for watering shrubs, foundations, planters, and the like. The present invention is applicable to all such systems. 
         [0032]      FIG. 1  also illustrates one method for installing the system of the present invention in an existing, in-ground sprinkler system. A section of supply line  12 , downstream of backflow preventer  14  may be removed and elbows  16  and risers  18  installed so that a portion of supply line  12  is accessible, preferably above grade. This portion of supply line  12  may include union  20  for ease of installation. Chemical dispenser  36  is plumbed in series with supply line  12 . Chemical container  34  is shown mounted to dispenser  36 . The system may include optional cap or plug  38  for ensuring the watertight integrity of dispenser  34  when a chemical container is not mounted thereon. Plug  38  may have the same thread configuration as the neck of container  34  such that it connects to dispenser  36  in the same way as a chemical container  34 . Alternatively, cap  38  may be provided with separate connection means for sealing engagement with the body of dispenser  36 . As shown in  FIG. 1 , dispenser  36  and the above-ground portion of supply line  12  may be concealed from view with shrubbery  32 . 
         [0033]      FIG. 2  illustrates an alternative second embodiment of the invention wherein chemical container  34 ′ is mounted below disperser  36 ′. In this embodiment, dispenser  36 ′ includes dip tube  40  for withdrawing a liquid chemical or chemical solution from container  34 ′ Dip tube  40  may be in threaded engagement with dispenser  36 ′ for ease of removal. Plug  38 ′ may be used to seal dispenser  36 ′ when container  34 ′ and dip tube  40  are not present. 
         [0034]    Also shown in  FIG. 2  is optional bypass line  21  and bypass valve  19  connected between risers  18 . Bypass valve  19  may be a 3-way valve which may direct the flow of water from supply line  12  to either dispenser  36  or through bypass line  21  to the distribution system. In some embodiments, bypass valve  19  may be an electrically-actuated valve and electrical control lines  26  may receive control signals from a remote timer and/or control station (not shown). 
         [0035]      FIG. 3  is a cross-sectional view of dispenser  36  according to the embodiment shown in  FIG. 1 . As shown by the outlined directional arrows in the drawing, irrigation water from supply line  12  flows through main passage  42 . Aspirator passage  44  is orthogonal to main passage  12  and of smaller diameter such that water flowing through main passage  42  creates a suction in aspirator line  44 . 
         [0036]    In the embodiment shown in  FIG. 3 , chemical container  34  is comprised of a bottle having externally-threaded neck  46 . Threaded neck  46  may accommodate a screw-type cap to contain liquid chemical  50  in container  34  when it is not mounted on dispenser  36 . Shoulder  52  may be formed on bottle neck  46  to limit the seating depth of neck  46  in internally-threaded connector  48  of dispenser  36 . 
         [0037]    The body of dispenser  36  may be machined from any suitable material such as a metal or metal alloy or may be molded with a thermoplastic material such as PVC. In  FIG. 3 , threaded connectors are used to attach dispenser  36  to water supply line  12 . Other connection means, including those well-known in the pipe fitting art, may be used. In embodiments wherein the body of dispenser  36  is formed of a synthetic polymer, the connection may be a solvent-welded connection. 
         [0038]    It will be appreciated that in order to attach a container of liquid chemical to a dispenser  36  of the type illustrated in  FIGS. 1 and 3 , it is necessary to invert the container. In order to prevent the chemical from spilling during this operation, it is preferable to equip the container  34  with valve means. One particular preferred embodiment of a valve means is illustrated in  FIGS. 3 and 4 . 
         [0039]    Referring now to  FIG. 4 , valve insert  56  has U-shaped perimeter section  62  which may connect to rim  54  of neck  46  of container  34  in sealing engagement. Container  34  may be a blow-molded, disposable, plastic bottle. 
         [0040]    As may also be seen in  FIG. 5 , valve insert  56  comprises concentric outer wall  57  (which may be a press fit in bottle neck  46 ), intermediate wall  58  and inner wall  59 . Openings  60  in the section between intermediate wall  58  and inner wall  59  are provided for the passage of air. Central channel  64  of valve insert  56  is sealed at its inner end by valve  66 . In the illustrated embodiment, valve  66  is fabricated from an elastomeric polymer material. The perimeter flap  68  of valve  66  seals apertures  60  and the central portion of valve  66  substantially seals central channel  64  of valve insert  56 . The center of valve  66  has a generally cylindrical region of reduced thickness which forms septum  67 . Slit  69  is provided in septum  67  to permit the flow of liquid chemical  50  from container  34  in response to suction produced by aspirator  44 . Preferably, slit  69  is produced by making a cut in septum  67 —i.e., slit  69  has no appreciable width and the sides of slit  69  seal against each other and substantially prevent the flow of liquid chemical  50  out of container  34  when it is inverted with normal, ambient pressure present on the open side of valve  66 . 
         [0041]    Referring now to the exploded view provided in  FIG. 6 , connector insert  73  includes cylindrical probe  70  having O-ring  75  in a groove on its outer circumference for sealing against the interior wall of central channel  64  of valve insert  56 . Probe  70  has a central passage terminating in orifice  71 . The feed rate of chemical  50  may be altered by varying the size (diameter) of orifice  71 . A pair of transverse slots  72  are provided in the upper surface of the body of connector insert  73 . These slots provide a passageway for air to enter container  34  as liquid  50  is withdrawn. The outer, circumferential surface of connector insert  73  has threads  74  for engagement with threaded connector  48  of dispenser  36 . Threads  74  have gap(s)  76  substantially aligned with slots  72  to provide a passageway for air. Slots  72  also provide an engagement surface for a tool used to install (or remove) insert  73  in threaded connector  48 . 
         [0042]    Connector  48  includes circumferential ring or ridge  80 . Connector insert  73  includes corresponding ring or ridge  82 . O-ring  84  fits between rings  80  and  82  for sealing engagement of connector insert  73  in threaded connector  48 . Screen  86  may be provided in the central passageway of dispenser  36  for preventing the entry of undissolved chemicals or foreign matter into the irrigation system to which it is attached. 
         [0043]    The second illustrated embodiment of the invention is depicted in  FIGS. 2 and 7 . In this embodiment, container  34 ′ attaches to dispenser  36 ′ on its undersurface—i.e., container  34 ′ need not be inverted in order to attach it to dispenser  36 ′. 
         [0044]    Container  34 ′ may be sealed by a screw-on cap (not shown) and membrane  90 . Membrane  90  may be formed of any suitable material as is well known in the art. Examples of sealing membrane materials include plastic polymers, metal foils, treated papers and laminates comprising one or more of these materials. Dip tube  40  is designed to pierce membrane  90 . To that end, dip tube  40  may comprise sharpened tip  100 . Dip tube  40  may also comprise section  98  of enlarged diameter. Enlarged diameter section  98  is provided near the distal end of tube  40  such that, when tip  100  pierces membrane  90  and section  98  is forced through membrane  90  a larger opening  92  than that merely required to accommodate the smaller diameter section of dip tube  40  is created. An annular opening  92  surrounding tube  40  permits air to enter headspace  93  via vent port  94  and vent passageway  96  as liquid chemical  50  is withdrawn from container  34 ′ thereby relieving the partial vacuum that would otherwise be created and which would substantially stop the aspiration of fluid through tube  40 . Dip tube  40  may comprise threaded connector  104  and seal  102  to permit the user to remove and replace dip tube  40 . As discussed above, it may be advantageous to remove dip tube  40  in order to permit the installation of cap or plug  38 ′ when container  34 ′ is not in place on dispenser  36 ′. 
         [0045]      FIG. 8  depicts an optional check valve  106  that may be provided in vent passageway  96  for preventing the evaporation of liquid chemical  50  from container  34 ′ and/or preventing the possible discharge of liquid chemical  50  through vent passageway  96  and vent port  94  in the event that the discharge side of dispenser  36 ′ becomes blocked. 
         [0046]    Valve  106  may be fabricated from natural rubber or a synthetic elastomeric polymer material. The valve action may be effected by means of flap  108  connected to the body of valve  106  via living hinge  112 . Circumferential ridge  110  may be provided to secure valve  106  in a corresponding groove in the wall of passageway  96 . 
         [0047]    Liquid chemical  50  may be any water-soluble or water-miscible chemical. Examples include fertilizers, pesticides, herbicides, fungicides, growth-enhancing agents, abscission agents, wetting agents, and the like. Oil-based chemicals may also be dispersed as an emulsion in water using the dispenser of the present invention. 
         [0048]    The operation of the embodiment of the invention illustrated in FIGS.  1  and  3 - 6  will now be described with reference to those drawing figures. The user selects a bottle  34  containing the desired treatment chemical(s) and removes the cap from the bottle. If installed, the user also removes plug or cap  38  from dispenser  36 . Bottle  34  is inverted and screwed into threaded connector  48  until shoulder  52  is seated on the rim of connector  48  or valve insert  56  contacts the flat, upper surface of connector insert  73 . During this installation operation, valve  66  substantially prevents the loss of chemical  50  from bottle neck  46 . 
         [0049]    Water flowing through main passage  42  produces a suction in aspirator passage  44 . This suction is sufficient to draw liquid chemical  50  through slit  69  in septum  67  and into aspirator passage  44 . Liquid chemical  50  mixes with water in main passage  42  of dispenser  36  and continues to mix with the water as it flows through the distribution system to the selected zone and out through sprinkler head  28 . As liquid is withdrawn from container  34 , a partial vacuum is produced. This is relieved by ambient air entering gap  81  in connector  48  and following the path depicted by the arrows in  FIG. 4 . Flap portion  68  of valve  66  opens in response to the reduced pressure within container  34  and air enters the interior of the container through apertures  60  in valve insert  56 . Chemical feed continues until the contents of container  34  are exhausted or the flow of water through main passage  42  ceases. Container  34  may remain in place on dispenser  34  even when empty without adversely affecting the operation of sprinkler system  10 . Alternatively, it may be removed and replaced with plug  38 . 
         [0050]    The operation of the embodiment illustrated in  FIGS. 2 ,  7  and  8  is similar. Cap  38 ′ is removed from dispenser  36 ′ (if installed). A container  34 ′ of liquid chemical  50  is selected and its top (not shown) is removed. If it was previously removed, dip tube  40  is installed by screwing threaded connector  104  into the body of dispenser  36 ′. Membrane  90  of container  34 ′ is now pressed against tip  100  of tube  40  with sufficient pressure to puncture membrane  90  and force larger diameter section  98  through membrane  90  forming a hole therein that is larger than the smaller diameter section of tube  40 . Container  34 ′ is screwed only dispenser  36 ′ and the flow of irrigation water through it is begun. The flow of water across the upper end of dip tube  40  produces a suction in the tube which withdraws liquid chemical  50  from container  34 ′ where it mixes in the main passageway of dispenser  36 ′ and continues downstream and out through sprinkler heads  28  in the selected zone. The partial vacuum produced in headspace  93  by the withdrawal of liquid contents of container  34 ′ is relieved by ambient air entering headspace  93  via vent port  94  and vent passageway  96  as shown by the arrows in  FIGS. 7 and 8 . Optional check valve  106  prevents supply water from main feed line  12  from passing through tube  40 , into the interior of container  34 ′ and out through vent port  94  when all downstream valves are closed. Container  34 ′ also may remain in place on dispenser  34 ′ even when empty without adversely affecting the operation of sprinkler system  10 . Alternatively, it may be removed and replaced with plug  38 ′. 
         [0051]    It should be appreciated that container  34  (or  34 ′) may be a disposable container. This feature, together with the action of valve  66  (in the first embodiment) or membrane  90  (in the second illustrated embodiment) provides significant safety benefits to the user. The chances of inadvertent contact with liquid chemical  50  (which may be toxic) are greatly reduced when the user need handle only the exterior of container  34  and disposes of the container following use. Valve  66  (or membrane  90 ) prevents liquid chemical  50  from splashing or spilling from container  34  (or  34 ′) during handling when its cap or lid is removed. 
         [0052]    As shown in  FIG. 2 , dispenser  36  or  36 ′ may be bypassed in certain embodiments with bypass valve  19  and bypass line  21 . In this way, chemical  50  may be applied only to certain selected zones and/or applied only during a portion of the watering cycle. For example, it may be desired to apply a weed-and-feed chemical only to those zones of sprinkler system  10  that apply water to lawn surfaces and not to zones for shrubs or gardens. If bypass valve  19  is electrically actuated, it may be connected to a central control station (not shown) that selects its position in response to the particular zone being watered and/or selects a certain valve position for a certain time interval. 
         [0053]    Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.