Abstract:
A freeze resistant sanitary hydrant is provided that employs a reservoir for storage of fluid under the frost line or in an area not prone to freezing. To evacuate this reservoir, a means for altering pressure is provided that is able to function in hydrant systems that employ a vacuum breaker.

Description:
This application is a continuation of U.S. patent application Ser. No. 13/048,445, filed Mar. 15, 2011, now U.S. Pat. No. 8,474,476, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/313,902, filed Mar. 15, 2010, and U.S. Provisional Patent Application Ser. No. 61/313,918, filed Mar. 15, 2010, the entire disclosures of which are incorporated by reference herein. 
     This application is also related to U.S. Pat. No. 8,042,565, U.S. Pat. No. 7,472,718, and U.S. Pat. No. 7,730,901, the entire disclosures of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of the present invention are generally related to contamination proof hydrants that employ a venturi that facilitates transfer of fluid from a self-contained water storage reservoir. 
     BACKGROUND OF THE INVENTION 
     Hydrants typically comprise a head interconnected to a water source by way of a vertically oriented standpipe that is buried in the ground or interconnected to a fixed structure, such as a roof. To be considered “freeze proof” hydrant water previously flowing through the standpipe must be directed away from the hydrant after shut off. Thus many ground hydrants  2  currently in use allow water to escape from the standpipe  6  from a drain port  10  located below the “frost line”  14  as shown in  FIG. 1 . 
     Hydrants are commonly used to supply water to livestock that will urinate and defecate in areas adjacent to the hydrant. It follows that the animal waste will leach into the ground. Thus a concern with freeze proof hydrants is that they may allow contaminated ground water to penetrate the hydrant through the drain port when the hydrant is shut off. More specifically, if a vacuum, i.e., negative pressure, is present in the water supply, contaminated ground water could be drawn into the standpipe and the associated water supply line. Contaminants could also enter the system if pressure of the ground water increases. To address the potential contamination issue, “sanitary” yard hydrants have been developed that employ a reservoir that receives water from the standpipe after hydrant shut off. 
     There is a balance between providing a freeze proof hydrant and a sanitary hydrant that is often difficult to address. More specifically, the water stored in the reservoir of a sanitary hydrant could freeze which can result in hydrant damage or malfunction. To address this issue, attempts have been made to ensure that the reservoir is positioned below the frost line or located in an area that is not susceptible to freezing. These measures do not address the freezing issue when water is not completely evacuated from the standpipe. That is, if the reservoir is not adequately evacuated when the hydrant is turned on, the water remaining in the reservoir will effectively prevent standpipe water evacuation when the hydrant is shut off, which will leave water above the frost line. 
     To help ensure that all water is evacuated from the reservoir, some hydrants employ a venturi system. A venturi comprises a nozzle and a decreased diameter throat. When fluid flows through the venturi a pressure drop occurs at the throat that is used to suction water from the reservoir. That is, the venturi is used to create an area of low pressure in the fluid inlet line of the hydrant that pulls the fluid from the reservoir when fluid flow is initiated. Sanitary hydrants that employ venturis must comply with AS SE-1057, ASSE-0100, and ASSE-0152 that require that a vacuum breaker or a backflow preventer be associated with the hydrant outlet to counteract negative pressure in the hydrant that may occur when the water supply pressure drops from time-to-time which could draw potentially contaminated fluid into the hydrant after shut off. Internal flow obstructions associated with the vacuum breakers and backflow preventers will create a back pressure that will affect fluid flow through the hydrant. More specifically, common vacuum breakers and backflow preventers employ at least one spring-biased check valve. When the hydrant is turned on spring forces are counteracted and the valve is opened by the pressure of the fluid supply, which negatively influences fluid flow through the hydrant. In addition an elongated standpipe will affect fluid flow. These sources of back pressure influence flow through the venturi to such a degree that a pressure drop sufficient to remove the stored water from the reservoir will not be created. Thus to provide fluid flow at a velocity required for proper functioning of the venturi, fluid diverters or selectively detachable backflow preventers, i.e., those having a quick disconnect capability, have been used to avoid the back pressure associated with the vacuum breakers of backflow preventers. In operation, as shown in  FIG. 2 , the diverter is used initially for about 45 seconds to ensure reservoir evacuation. Then, the diverter is disengaged so that the water will flow through the backflow preventer or vacuum breaker. The obvious drawback of this solution is that the diverter must be manually actuated and the user must allow water to flow for a given amount of time, which is wasteful. 
     Further, as the standpipe gets longer it will create more backpressure, i.e., head pressure, that reduces the flow of water through the venturi, and at some point a venturi of any design will be unable to evacuate the water in the reservoir. That is, the amount of time it takes for a hydrant to evacuate the water into the reservoir depends on the height/length of the standpipe as well as the water pressure. The evacuation time of roof hydrants of embodiments of the present invention, which has a 42″ standpipe, is 5 seconds at 60 psi. The evacuation time will increase with a lower supply pressure or increased standpipe length or diameter. Currently existing hydrants have evacuation times in the 30 second range. 
     Another way to address the fluid flow problem caused by vacuum breakers is to provide a reservoir with a “pressure system” that is capable of holding a pressure vacuum that is used to suction water from the standpipe after hydrant shut off. During normal use the venturi will evacuate at least a portion of the fluid from the reservoir. Supply water is also allowed to enter the reservoir which will pressurize any air in the reservoir that entered the reservoir when the reservoir was at least partially evacuated. When flow through the hydrant is stopped, the supply pressure is cut off and the air in the reservoir expands to created a pressure drop that suctions water from the standpipe into the reservoir. If the vacuum produced is insufficient, which would be attributed to incomplete evacuation of the reservoir, water from the standpipe will not drain into the reservoir and water will be left above the frost line. 
     Other hydrants employ a series of check valves to prevent water from entering the reservoir during normal operations. Hydrants that employ a “check system” uses a check valve to allow water into or out of the reservoir. When the hydrant is turned on, the check valve opens to allow the water to be suctioned from the reservoir. The check also prevents supply water from flowing into the reservoir during normal operations, which occurs during the operation of the pressure vacuum system. When the hydrant is shut off, the check valve opens to allow the standpipe water to drain into the reservoir. One disadvantage of a check system is that it requires a large diameter reservoir to accommodate the check valve. Thus a roof hydrant would require a larger roof penetration and a larger hydrant mounting system, which may not be desirable. 
     Another issue associated with both the pressure vacuum and check systems is that there must be a passageway or vent that allows air into the reservoir so that when a hydrant is turned on, the water stored in the reservoir can be evacuated. If the reservoir was not exposed to atmosphere, the venturi would not create sufficient suction to overcome the vacuum that is created in the reservoir. 
     SUMMARY OF THE INVENTION 
     It is one aspect of embodiments of the present invention to provide a sanitary and freeze proof hydrant that employs a venturi for suctioning fluid from a fluid storage reservoir. As one of skill in the art will appreciate, the amount of suction produced by the venturi is a function of geometry. More specifically, the contemplated venturi is comprised of a nozzle with an associated throat. Water traveling through the nozzle creates an area of low pressure at or near the throat that is in fluid communication with the reservoir. In one embodiment, the configuration of the nozzle and throat differs from existing products. That is, the contemplated nozzle is configured such that the venturi will operate in conjunction with a vacuum breaker, a double check backflow preventer, or a double check backflow prevention device as disclosed in U.S. Patent Application Publication No. 2009/0288722, which is incorporated by reference in its entirety herein, without the need for a diverter. Preferably, embodiments of the present invention are used in conjunction with the double check backflow prevention device of the &#39;722 publication as it is less disruptive to fluid flow than the backflow preventers and vacuum breakers of the prior art. 
     While the use of a venturi is not new to the sanitary yard hydrant industry, the design features of the venturi employed by embodiments of the present invention are unique in the way freeze protection is provided. More specifically, current hydrants employ a system that allows water to bypass a required vacuum breaker. For example, the Hoeptner Freeze Flow Hydrant employs a detachable vacuum breaker and the Woodford Model S3 employs a diverter. Again, fluid diversion is needed so that sufficient fluid flow is achieved for proper venturi functions. The venturi design of sanitary hydrants of the present invention is unique in that the venturi will function properly when water flows through the vacuum breaker or double check backflow preventer—no fluid diversion at the hydrant head is required. This allows the hydrant to work in a way that is far more user friendly, because the hydrant is able to maintain its freeze resistant functionality without requiring the user to open a diverter, for example. Embodiments of the present invention are also environmentally friendly as resources are conserved by avoiding flowing water out of a diverter. 
     It is another aspect of the embodiments of the invention is to provide a hydrant that operates at pressures from about 20 psi to 125 psi and achieves a mass flow rate above 3 gallons per minute (GPM) at 25 psi, which is required by code. One difficult part of optimizing the flow characteristics to achieve these results is determining the nozzle diameter. It was found that a throat diameter change of about 0.040 inches would increase the mass flow rate by 2 GPM. That same change, however, affects the operation of the venturi. For example, hydrants with a nozzle diameter of 0.125 inches will provide acceptable reservoir evacuation but would not have the desired mass flow rate. A 0.147 inch diameter nozzle will provide an acceptable mass flow rate, but reservoir evacuation time was sacrificed. In one embodiment of the present invention a venturi having a nozzle diameter of about 0.160 inches is employed. 
     It is another aspect of the present invention to provide a nozzle having an exit angle that facilitates fluid flow through the venturi. More specifically, the nozzle exit of one embodiment possesses a gradual angle so that fluid flowing through the venturi maintains fluid contact with the surface of the nozzle and laminar flow is generally achieved. In one embodiment the exit angle is between about 4 to about 5.6 degrees. For example, nozzle exit having very gradual surface angle, e.g. 1-2 degrees, will evacuate the reservoir more quickly, but would require an elongated venturi. Thus, an elongated venturi may be used to reduce back pressure associated with the venturi, but doing so will add cost. The nozzle inlet may have an angle that is distinct from that of the exit to facilitate construction of the venturi by improving the machining process. 
     It is thus one aspect of the present invention to provide a sanitary hydrant, comprising: a standpipe having a first end and a second end; a head for delivering fluid interconnected to said first end of said standpipe; a fluid reservoir associated with said second end of said standpipe; a venturi positioned within said reservoir and interconnected to said second end of said standpipe, said venturi comprised of a first end, which is interconnected to said standpipe, and a second end associated with a fluid inlet valve with a throat between said first end and said second end of said venturi; a bypass tube having a first end interconnected to a location adjacent to said first end of said venturi and a second end interconnected to a bypass valve, said bypass valve also associated with said second end of said venturi, wherein when said bypass valve is opened, fluid flows from said inlet valve, through said bypass tube, through said standpipe, and out said hydrant head; and wherein when said bypass valve is closed, fluid flows through said venturi, thereby creating a pressure drop adjacent to said throat that communicates with said reservoir to draw fluid therefrom. 
     It is another aspect to provide a method of evacuating a sanitary hydrant, comprising: providing a standpipe having a first end and a second end; providing a head for delivering fluid interconnected to said first end of said standpipe; providing a fluid reservoir associated with said second end of said standpipe; providing a venturi positioned within said reservoir and interconnected to said second end of said standpipe, said venturi comprised of a first end, which is interconnected to said standpipe, and a second end associated with a fluid inlet valve with a throat between said first end and said second end of said venturi; providing a bypass tube having a first end interconnected to a location adjacent to said first end of said venturi and a second end interconnected to a bypass valve, said bypass valve also associated with said second end of said venturi, wherein when said bypass valve is opened, fluid flows from said inlet valve, through said bypass tube, through said standpipe, and out said hydrant head; and wherein when said bypass valve is closed, fluid flows through said venturi, thereby creating a pressure drop adjacent to said throat that communicates with said reservoir to draw fluid therefrom initiating fluid flow through said head by actuating a handle associated therewith; actuating a bypass button that opens the bypass valve such that fluid is precluded from entering said venturi; actuating said bypass button to close said bypass valve; flowing fluid through said venturi; evacuating said reservoir; ceasing fluid flow through said hydrant; and draining fluid into said reservoir. 
     The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. Moreover, references made herein to “the present invention” or aspects thereof should be understood to mean certain embodiments of the present invention and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detail Description, particularly when taken together with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of these inventions. 
         FIGS. 1A-1C  are a depiction of the operation of a hydrant of the prior art; 
         FIGS. 2A-2C  are a series of figures depicting the use of a flow diverter of the prior art; 
         FIG. 3  is a cross section of a venturi of the prior art; 
         FIG. 4  is a perspective view of a venturi system employed by the prior art; 
         FIG. 5  is a perspective view of one embodiment of the present invention; 
         FIG. 6  is a detailed view of the venturi system of the embodiment of  FIG. 5 ; 
         FIG. 7  is a perspective view similar to that of  FIG. 6  wherein the reservoir has been omitted for clarity; 
         FIG. 8  is a cross sectional view of a venturi system that employs a bypass tube of one embodiment of the present invention; 
         FIG. 9  is a cross sectional view of a bypass valve used in conjunction with the embodiment of  FIG. 5  shown in an open position; 
         FIG. 10  shows the bypass valve of  FIG. 9  in a closed position; 
         FIG. 11  is a top perspective view of one embodiment of the present invention showing a bypass button and an electronic reservoir evacuation button; 
         FIG. 12  is a graph showing sanitary hydrant comparisons; 
         FIG. 13  is a perspective view of a venturi system of another embodiment of the present invention; 
         FIG. 14  is a detailed cross sectional view of  FIG. 13  showing the check valve in a closed position when the hydrant is on; 
         FIG. 15  is a detailed cross sectional view of  FIG. 13  showing the check valve in an open position when the hydrant is off; 
         FIG. 16  is a cross sectional view showing a hydrant of another embodiment of the present invention; 
         FIG. 17  is a detail view of  FIG. 16 ; 
         FIG. 18  is a detail view of  FIG. 17   
         FIG. 19  is a cross section of another embodiment of the present invention; and 
         FIG. 20  is a table showing a comparison of various hydrant assemblies and the operation cycle of each. 
     
    
    
     It should be understood that the drawings are not necessarily to scale, but that relative dimensions nevertheless can be determined thereby. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
     To assist in the understanding of one embodiment of the present invention the following list of components and associated numbering found in the drawings is provided herein: 
     
       
         
               
               
             
               
               
             
           
               
                   
               
               
                 # 
                 Component 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 Hydrant 
               
               
                 4 
                 Head 
               
               
                 5 
                 Handle 
               
               
                 6 
                 Standpipe 
               
               
                 10 
                 Drain port 
               
               
                 14 
                 Frost line 
               
               
                 18 
                 Venturi 
               
               
                 22 
                 Diverter 
               
               
                 26 
                 Vacuum breaker 
               
               
                 30 
                 Siphon tube 
               
               
                 34 
                 Check valve 
               
               
                 36 
                 Outlet 
               
               
                 37 
                 Venturi vacuum inlet and drain port 
               
               
                 38 
                 Hydrant inlet valve 
               
               
                 42 
                 Bypass 
               
               
                 46 
                 Bypass button 
               
               
                 50 
                 Casing cover 
               
               
                 54 
                 Piston 
               
               
                 56 
                 Bypass valve 
               
               
                 57 
                 Control rod 
               
               
                 58 
                 Secondary spring operated piston 
               
               
                 59 
                 Bottom surface 
               
               
                 60 
                 EFR button 
               
               
                 64 
                 LED 
               
               
                 68 
                 Screen piston 
               
               
                 72 
                 Reservoir 
               
               
                 76 
                 Check valve piston 
               
               
                 80 
                 Vent 
               
               
                 82 
                 Inlet Check Valve 
               
               
                 84 
                 Outlet Check Valve 
               
               
                 86 
                 Fixed Inlet Volume 
               
               
                 88 
                 Fixed Outlet Volume 
               
               
                 90 
                 Valve Body 
               
               
                 92 
                 Inlet Check Body 
               
               
                 94 
                 Inlet Check Spring 
               
               
                 96 
                 Valve Cap 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION 
     The venturi  18  and related components used in the hydrants of the prior art is shown in  FIGS. 3 and 4  and functions when the hydrant issued in conjunction with a vacuum breaker and a diverter. The diverter is needed to allow the venturi to work properly in light of the flow obstructions associated with the vacuum breaker. A typical on/off cycle for this hydrant (see also  FIG. 2 ) requires that the user open the hydrant to cause water to exit the diverter  22  and not the vacuum breaker  26 . As the water flows out of the diverter  22 , a vacuum is created that draws water through a siphon tube  30  and check valve  34 , which evacuates the reservoir (not shown). Flowing water through the diverter  22  for about 30 to 45 seconds will generally evacuate the reservoir. Next, as shown in  FIG. 2 , the diverter  22  is pulled down to redirect the water out of the vacuum breaker  26 . The vacuum breaker  26  allows the hydrant  2  to be used with an attached hose and/or a spray nozzle as the vacuum breaker  26  will evacuate the head when the hydrant  2  is shut off, thereby making it frost proof. When the water is flowing out of the vacuum breaker  26  the venturi  18  will stop working and the one-way check valve  34  will prevent water from entering the reservoir. Once the hydrant is shut off, the water in the standpipe  6  will drain through a venturi vacuum inlet and drain port  37  that is in fluid communication with the reservoir similar to that disclosed in U.S. Pat. No. 5,246,028 to Vandepas, which is incorporated by reference herein. The check valve  34  is also pressurized when the hydrant is turned off because the shut off valve  38  is located above the check valve  34 . 
     A venturi assembly used in other hydrants that employ a pressurized reservoir also provides a vacuum only when water flows through a diverter. A typical on/off cycle for a hydrant that uses this venturi configuration is similar to that described above, the exception being that a check valve that prevents water from entering the reservoir is not used. When the diverter is transitioned so water flows through the vacuum breaker, the backpressure created thereby will cause water to fill and pressurize the reservoir, which prevents water ingress after hydrant shut off. As the reservoir is at least partially filled with water during normal use, the user needs to evacuate the hydrant after shut off by removing any interconnected hose and diverting fluid for about 30 seconds, which will allow the venturi to evacuate the water from the reservoir. 
     A hydrant of embodiments of the present invention shown in  FIGS. 5-11  which may employ a venturi with an about ⅛″ diameter nozzle. To account for the decrease in mass flow and associated back pressure that affects the functionality of the venturi described above, a bypass  42  is employed. More specifically, the bypass  42  maintains the flow rate out of the hydrant head  4  and allows for water to be expelled from the head  4  at the expected velocity. Fluid bypass is triggered by actuating a button  46  located on the casing cover  50  as shown in  FIG. 11 . When the hydrant is turned on the user pushes the bypass button  46  that will in turn move a bypass piston  54  of a bypass valve  56  into the open position as shown in  FIG. 9 . This will allow water to bypass the venturi  2  and re-enter the standpipe above the restriction caused by the venturi. The increased flow rate is greater than could be achieved with a venturi alone, even if the diameter of the venturi nozzle was increased. 
     While the bypass allows the mass flow rate to increase greatly, it also causes the venturi to stop creating a vacuum that is needed to evacuate the reservoir. Before normal use, the bypass piston  54  is closed as shown in  FIG. 10 . Similar to the system described in  FIG. 16  below, the venturi  18  and associated bypass  42  are associated with a control rod  57  that is associated with the hydrant handle  5 . Opening of the hydrant transitions the control rod  57  upwardly, which pulls the venturi  18  and associated bypass  42  upwardly and opens the hydrant inlet valve  38  to initiate fluid flow. Conversely, transitioning the hydrant handle  5  to a closed position will move the venturi  18  and associated bypass  42  downwardly such that a secondary spring operated piston  58  of the bypass valve  56  well contact a bottom surface  59  of the reservoir. As the secondary spring piston  58  contacts the bottom surface  59 , the bypass valve  54  moves to a closed position as shown in  FIG. 10 . Moving the handle  5  to an open position to initiate fluid flow through the hydrant head will separate the secondary spring operated piston  58  from the bottom surface  59  of the reservoir which allows the bypass piston  54  to move to an open position as shown in  FIG. 9  when the bypass button  46  is actuated. When the bypass  42  is in the closed position, water is forced to flow through the venturi causing a vacuum to occur, thereby causing the reservoir to be evacuated each time the hydrant is used. After water flows from the vacuum breaker for a predetermined time, the user will actuate the bypass button  46  which opens the bypass valve  56  to divert fluid around the venturi  2 . The secondary spring operated piston  58 , which is designed to account for tolerances making assembly of the hydrant easier. The secondary spring operated piston  58  also makes sure the hydrant will operate properly if there are any rocks or debris present in the hydrant reservoir. 
     The venturi  18  of this embodiment can be operated in a 7′ bury hydrant with a minimum operating pressure of 25 psi. The other major exception is the addition of the aforementioned bypass valve  56  that allows the hydrant to achieve higher flow rates. 
     In operation with a hose, initially the hose is attached to the backflow preventer  26  or the bypass button is pushed to that the venturi will not operate correctly and the one way check valve  34  will be pressurized in such a way to prevent flow of fluid from the reservoir. After the hydrant is shut off, the hose is removed from vacuum breaker  26 . Next the hydrant  2  is turned on and water flows through the vacuum breaker  26  for about 30 seconds. When there is no hose attached, and the bypass has not been activated, the venturi  18  will create a vacuum that suctions water from the reservoir  72  and making the hydrant frost proof. Thus when the hydrant is later shut off, the check valve piston will move up and force open the one way check valve  34  to allow water in the hydrant to drain into the reservoir. This operation will also reset the bypass valve  56  into the closed position. 
     Some embodiments of the present invention will also be equipped with an Electronic Freeze Recognition (EFR) device as shown in  FIG. 11 . The EFR includes a button  60  that allows the user to ascertain if the water has been evacuated from the standpipe  6  properly and if the hydrant is ready for freezing weather. The device uses a circuit board in concert with a dual color LED  64  as shown in  FIG. 11  to warn the operator of a potential freezing problem. When the EFR button  60  is pushed and the LED  64  glows red it indicates that the hydrant has not been evacuated properly. This informs the operator that the water in the reservoir is above the frost line, and the hydrant needs to be evacuated by the method described above. A green LED  64  indicates the hydrant has been operated properly and the hydrant is ready for freezing weather. 
     Flow rates for hydrants of embodiments of the present invention compare favorably with existing sanitary hydrants on the market, see  FIG. 12 . The prior art models are compared with hydrants that use a vacuum breaker and hydrants that use a double check backflow preventer. The venturi and related bypass system will meet ASSE 1057 specifications. 
     Another embodiment of the present invention is shown in  FIGS. 13-15  that does not employ a bypass. Variations of this embodiment employ an about 0.147 to an about 0.160 diameter nozzle, which allows for a flow rate of 3 gallons per minute at 25 psi and evacuation of the reservoir at 20 psi. As this configuration meets the desired mass flow characteristics, a bypass is not required to obtain the mass flow rate, and therefore this hydrant can be produced at a lower cost. This embodiment also employs a dual-use check valve. The check valve is closed by a spring when the hydrant is turned on as shown in  FIG. 14  to prevent water from filling the reservoir. Again, when water is flowing through the double check backflow preventer a suction can still be produced to pull water from the reservoir through this check valve. When the hydrant is turned off, a screen piston  68  moves up when it contacts the bottom surface  59  of the reservoir which forces the check valve  34  into the open position as shown in  FIG. 15 . This allows the water in the hydrant to drain into the reservoir, thereby making the hydrant freeze resistant. Other embodiments of the present invention employ a venturi to evacuate a reservoir, but do not need a diverter to operate correctly. More specifically, a venturi is provided that will evacuate a reservoir through a double check backflow preventer. 
     The check valve  34  depicted in  FIGS. 14 and 15  is a double check valve  34  comprising an inlet check valve  82  and an outlet check valve  84 . A fixed inlet volume  86  and a fixed outlet volume  88  are at least partially defined within a valve body  90  of the double check valve  34 . A valve cap  96  at least partially defines the fixed inlet volume  86  and secures the components of the inlet check valve  82 , and the fixed inlet volume  86  provides space components of the inlet check valve  82 . Similarly, the fixed outlet volume  88  provides space for components of the outlet check valve  84 . 
     In the embodiment depicted in  FIGS. 14 and 15 , the inlet check valve  82  comprises an inlet check body  92  and an inlet check spring  94 . Other embodiments may optionally include an inlet check seal that is disposed about the inlet check body  92 . The inlet check body  92  is disposed in the inlet check spring  94  such that the inlet check body  92  is biased downward. When the inlet check body  92  is fully biased downward, the inlet check body prevents fluid flow from the inlet check valve  82  into the outlet check valve  84 , but allows fluid flow from the outlet check valve  84  into the inlet check valve  82 . 
     The outlet check valve  84  depicted in  FIGS. 14 and 15  comprises a screen piston  68 . The screen portion of the screen piston  68  filters any rocks or debris from the reservoir  72 .  FIG. 15  depicts the double check valve  34  in the closed position where the screen of the screen piston  68  contacts a bottom surface  59  of the reservoir  72 . This drives the screen piston  68  upward into the inlet check body  92  such that a seal between the inlet check body  92  and the valve body  90  is broken and fluid may drain into the reservoir  72 . 
       FIGS. 16-18  show a hydrant of another embodiment of the present invention that is simpler and more user friendly than sanitary hydrants currently in use. This hydrant is limited to a 5′ bury depth and a minimum working pressure of about 40 psi, which maximizes the venturi flow rate potential, while still being able to evacuate the reservoir as water flows through a double check. A one-way check valve  34  is provided that is forced open when the hydrant is shut off as shown in  FIG. 17 . 
     In operation, this venturi system operates similar to those described above with respect to  FIGS. 5-11 . More specifically, the venturi is interconnected to a movable control rod  57  that is located within the standpipe  6 . The handle  5  of the hydrant is thus ultimately interconnected to the venturi  18  and by way of the control rod  57 . To turn on the hydrant, the user moves the handle  5  to an open position, which pulls the control rod  57  upwardly and opens the inlet valve  38  such that water can enter the venturi  18 . Pulling the venturi upward also removes the check valve  34  upwardly such that the screen piston  68  moves away from the bottom surface  59  of the hydrant  2 . To turn the hydrant off, the handle  5  is moved to a closed position which moves the control rod  57  downwardly to move the venturi  18  downwardly to close the inlet valve  38 . Moving the venturi downwardly also transitions the screen piston  68  which opens the check valve  34 . To allow for evacuation reservoir a vent  80  may be provided on an upper surface of the hydrant. 
     Generally, this hydrant functions when a hose is attached to the backflow preventer. When the hose is attached, the venturi will not operate correctly and the pressure acting on the one way check valve  34  will prevent water ingress into the reservoir  72 . After the hydrant is shut off, the hose is removed from vacuum breaker, the hydrant must be turned on so that the water can flow through the double check vacuum preventer for about 15 seconds. That is, when there is no hose attached, the venturi will create a vacuum sufficient enough to suction water from the reservoir  72 , and making the hydrant frost proof. When the hydrant is later shut off, the check valve piston  26  will move up and force the one way check valve to an open position which allows the water in the hydrant to drain into the reservoir  72 . 
       FIG. 19  shows yet another hydrant of embodiments of the present invention that is designed specifically for mild climate use (under 2′ bury) and roof hydrants. The outer pipe of the roof hydrant is a smaller 1½ diameter PVC, instead of the 3″ used in some of the embodiments described above. This hydrant uses a venturi without a check valve in concert with a pressurized reservoir, a diverter is not used. The operation is the same as described above with respect to hydrant with a pressurized reservoir, with the evacuation of the reservoir being completed after the user detaches the hose. 
       FIG. 20  is a table comparing the embodiments of the present invention, which employ an improved venturi of that employ a bypass system, with hydrants of the prior art manufactured by the Assignee of the instant application. The embodiment shown in  FIG. 7 , for example, provides an increased flow rate, has an increased bury depth, and can operate at lower fluid inlet pressures. The evacuation time is discussed over the prior art. 
     While various embodiments of the present invention have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the following claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. For example, aspects of inventions disclosed in U.S. Pat. Nos. and Published Patent Application Nos. 5,632,303, 5,590,679, 7,100,637, 5,813,428, and 20060196561, all of which are incorporated herein by this reference, which generally concern backflow prevention, may be incorporated into embodiments of the present invention. Aspects of inventions disclosed in U.S. Pat. Nos. 5,701,925 and 5,246,028, all of which are incorporated herein by this reference, which generally concern sanitary hydrants, may be incorporated into embodiments of the present invention. Aspects of inventions disclosed in U.S. Pat. Nos. 6,532,986, 6,805,154, 6,135,359, 6,769,446, 6,830,063, RE39,235, 6,206,039, 6,883,534, 6,857,442 and 6,142,172, all of which are incorporated herein by this reference, which generally concern freeze-proof hydrants, may be incorporated into embodiments of the present invention. Aspects of inventions disclosed in U.S. Pat. Nos. and Published Patent Application Nos. D521,113, D470915, 7,234,732, 7,059,937, 6,679,473, 6,431,204, 7,111,875, D482,431, 6,631,623, 6,948,518, 6,948,509, 20070044840, 20070044838, 20070039649, 20060254647 and 20060108804, all of which are incorporated herein by this reference, which generally concern general hydrant technology, may be incorporated into embodiments of the present invention.