Patent Publication Number: US-2022235873-A1

Title: Vacuum sewage systems with check valves and check valves for vacuum sewage systems

Description:
The present invention relates generally to sewage systems which utilize differential pressures to produce sewage transport through the system, which are commonly referred to as “vacuum sewage systems” and, in particular, to vacuum sewage systems having a check valve and to check valves for vacuum sewage system. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Vacuum sewage systems typically employ a valve and a controller that opens the valve under certain operating conditions in order to discharge accumulated sewage from a collection tank, through the valve, and to a collection station via a discharge conduit. Under certain operating conditions, backpressure can occur that tends to force sewage from the discharge conduit into the controller. Certain prior art systems have utilized check valves in order to prevent sewage from being forced from the discharge conduit into the controller under such backpressure conditions. An example of such a check valve is shown in U.S. Pat. No. 4,171,853. 
     In one embodiment of the present invention, a check valve for a vacuum sewage system includes a body, a sealing member, a cover, and a retaining member. The body includes a post and a housing. The post has a first end, a second end, and a passageway extending from the first end to the second end. The housing has a groove, an open end, a flange disposed about the open end and having a protrusion, a closed end, and a chamber in fluid communication with the post passageway. The chamber has a floor disposed at an angle to the post passageway, a first sealing surface and a second sealing surface. The sealing member has a front face, a first section having a protrusion, a second section extending from first section, a third section extending from second section, a curved section connected to third section and having at least one opening, and a central section connected to curved the section. The central section of the sealing member has a sealing surface. The cover includes an open end, a side wall having a protrusion, a beveled edge and an inner surface, a front wall having a central section having a sealing surface, an interior chamber, an interior groove, and a connector extending from the front wall. The connector has a passageway in communication with the interior chamber. The retaining member is located in the groove of the housing and secures the cover to the housing. The retaining member has a first end, a second end and an opening between the first end and the second end. The flange of the housing is located in the interior groove of the cover. The second section of the sealing member is located between the first sealing surface of the housing chamber and the front wall of the cover. The second section of the sealing member is located adjacent the second sealing surface of the housing chamber. The protrusion of the sealing member is located in the protrusion of the housing. The protrusion of the sealing member and the protrusion of the housing flange are located in the protrusion of the cover. 
     In one embodiment, at least a portion of the floor of the chamber housing angles downwardly from the open end toward the post passageway. 
     In another embodiment, the central section of the sealing member is moveable from a first position in which the sealing surface of the sealing member is in contact with the sealing surface of the central section of the front wall of the cover, to a second position in which the sealing surface of the central section of the sealing member is spaced apart from the sealing surface of the central section of the front wall of the cover. In certain embodiments, the sealing surface of the central section of the sealing member closes one end of the connector passageway when the central section of the sealing member is in the first position. In another embodiment, an annular space is formed around the central section of the front wall of the cover and between the curved section of the sealing member and the front wall of the cover when the central section of the sealing member is in the first position. 
     In certain embodiments of the invention, the at least one opening in the sealing member is larger than the smallest cross-section of the connector passageway. In another embodiment, the smallest cross-section of the post passageway is larger than the smallest cross-section of the connector passageway. In some embodiments, the at least one opening in the sealing member and the smallest cross-section of the post passageway are both larger than the smallest cross-section of the connector passageway. 
     In other embodiments, the retaining member exerts outward force on the inner surface of the sidewall of the cover. 
     In another embodiment, the housing further includes a port for connection to an electronic air admission controller. In one embodiment, the housing further includes a connector for a device for monitoring the operational state of the vacuum sewage system. 
     In one embodiment of the present invention, a check valve for a vacuum sewage system has a body, a sealing member and a cover. The body includes a housing. The sealing member has a first section and a central section connected to the first section. The central section of the sealing member has a sealing surface. The cover has an interior chamber, a connector having a passageway in communication with the interior chamber, and a front wall having a central section. The central section of the front wall has a sealing surface. The central section of the sealing member is moveable from a first position in which the sealing surface of the sealing member is in contact with the sealing surface of the central section of the front wall of the cover, to a second position in which the sealing surface of the central section of the sealing member is spaced apart from the sealing surface of the central section of the front wall of the cover. 
     In one embodiment, the sealing surface of the central section of the sealing member closes one end of the connector passageway when the central section of the sealing member is in the first position. 
     In other embodiments, an annular space is formed around the central section of the front wall of the cover and between the first section of the sealing member and the front wall of the cover when the central section of the sealing member is in the first position. 
     In certain embodiments, the sealing member includes at least one opening. In one embodiment, the at least one opening is in the first section of the sealing member. In another embodiment, the at least one opening in the sealing member is larger than the smallest cross-section of the connector passageway. In a further embodiment, the opening in the sealing member is fluid communication with the annular space. 
     In other embodiments, the housing includes an open end and a chamber, and the body further includes a post having a first end, a second, and a passageway in fluid communication with the chamber and extending from the first end of the post to the second end of the post. In certain embodiments, the chamber includes a floor, at least a portion of which angles downwardly from the open end toward the post passageway. 
     In one embodiment of the present invention, a check valve for a vacuum sewage system includes a body, a cover and a sealing member, The body includes a housing. The cover includes an interior chamber, a connector having a passageway in communication with the interior chamber, and a front wall having a central section. The central section of the front wall has a sealing surface. The sealing member has a first section and a central section connected to the first section. The central section of the sealing member has a sealing surface facing the front wall of the cover. The check valve further includes means for facilitating the passage of fluid from between the sealing member and the front wall of the cover to the opposite side of the sealing member. 
     In one embodiment, the means for facilitating the passage of fluid includes at least one opening in the sealing member. 
     In one embodiment of the present invention, a vacuum sewage system includes a controller, a vacuum pump for providing vacuum to the vacuum sewage system and to the controller, and a check valve. The check valve has a cracking pressure sufficiently low so as to not cause a reduction of the vacuum supply to the controller upon opening of the check valve. 
     In one embodiment, the cracking pressure is less than 1 inch of mercury vacuum. In other embodiments, the controller is actuated at a vacuum pressure of 5 inches of mercury. 
     In certain embodiments, the rate of air flow through the check valve is greater than the rate of air flow through the controller. 
     These and other features of the present invention will be apparent to those of ordinary skill in the art from the following Detailed Description of Embodiments of the Invention and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a section of a vacuum sewage system according to one embodiment of the present invention. 
         FIG. 2A  is a side perspective view of a controller that is a component of the vacuum, sewage system shown in  FIG. 1 . 
         FIG. 2B  is a bottom perspective view of the controller shown in  FIG. 2A . 
         FIG. 2C  is an end view of the controller shown in  FIG. 1 . 
         FIG. 3  is a cross sectional view taken along line  3 - 3  in  FIG. 2C  showing the controller in the standby state. 
         FIG. 3A  is an enlarged view of detail  3 A in  FIG. 3 . 
         FIG. 3B  is an enlarged view of detail  3 B in  FIG. 3 . 
         FIG. 3C  is an enlarged view of detail  3 C in  FIG. 3 . 
         FIG. 3D  is an enlarged view of detail  3 D in  FIG. 3 . 
         FIG. 3E  is an enlarged view of detail  3 E in  FIG. 3 . 
         FIG. 4  is a cross sectional view taken along line  4 - 4  in  FIG. 3 . 
         FIG. 5  is a cross sectional view taken along line  5 - 5  in  FIG. 3 . 
         FIG. 6  is an enlarged view of detail  6  in  FIG. 3 . 
         FIG. 7  is a cross sectional view taken along line  3 - 3  in  FIG. 2A  showing the controller in the activated state. 
         FIG. 7A  is an enlarged view of detail  7 A in  FIG. 7 . 
         FIG. 7B  is an enlarged view of detail  7 B in  FIG. 7 . 
         FIG. 7C  is an enlarged view of detail  7 C in  FIG. 7 . 
         FIG. 8  is an exploded perspective view of a check valve according to one embodiment of the present invention that is a component of the vacuum sewage system shown in  FIG. 1 . 
         FIG. 9  is a front elevational view of the check valve shown in  FIG. 8 . 
         FIG. 10  is a top plan view of the check valve shown in  FIG. 8 . 
         FIG. 11  is a cross-sectional view of the check valve shown in  FIG. 8  in the standby state. 
         FIG. 12  is a cross-sectional view of the check valve shown in  FIG. 8  in the activated state. 
         FIG. 13  is an enlarged view of the detail shown in area  13  in  FIG. 11 . 
         FIG. 14  is an elevational view of a collection station that is a component of a vacuum sewage system according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION 
       FIG. 1  illustrates a vacuum sewage system  10  including a check valve  500  according to one embodiment of the present invention. System  10  includes gravity sewer conduits  20  at atmospheric pressure which drain from a sewage origination point, such as a toilet. Conduits  20  transport sewage to a holding tank  30 , which is maintained at atmospheric pressure. A sensor pipe  40  and a discharge conduit  50  extend into tank  30 . A first end  41  of pipe  40  extends downwardly into tank  30  to a point spaced above the inlet opening  51  of a discharge conduit  50 . The second end  42  of pipe  40  extends into a valve pit  60 . 
     Discharge conduit  50  extends into the valve pit  60  to a valve  70 . Numerous types of valves  70  are known in the industry. One example of a valve  70  that can be used with system  10  is disclosed in U.S. Pat. No. 4,171,853. Valve  70  is operated by a controller  80 , which will be described in greater detail below. The section of discharge conduit  50  downstream from valve  70  is maintained at vacuum or low pressure by a source of applied vacuum, such as, for example, one or more vacuum pumps VP, which may be located at a collection station CS. ( FIG. 14 ) Vacuum pumps VP are cycled on and off to maintain the vacuum sewage system at the desired vacuum level for proper system operation. Collection station CS also includes a collection tank CT, one or more sewage pumps SP, and a sewage discharge conduit SDC. Vacuum pumps VP draw a vacuum on collection tank CT and through discharge conduits  50 . Sewage pumps SP discharge sewage from collection tank CT through sewage discharge conduit SDC to a sewage treatment facility (not shown). Collection stations suitable for use with the present invention are disclosed, for example, in U.S. Pat. Nos. 4,179,371 and 10,316,504. 
     In use, sewage is discharged through conduit  20  into tank  30 . Under preselected pressure conditions in tank  30  (i.e. when the sewage content of tank  30  is such that a discharge cycle is warranted) valve  70  is opened by controller  80 . Opening valve  70  creates a differential pressure between the relatively low pressure or vacuum portion of discharge conduit  50  downstream from valve  70  and the relatively higher or atmospheric pressure portion of discharge conduit  50  upstream from valve  70 . This pressure differential causes discharge of the sewage in tank  30  through inlet opening  51  of discharge conduit  50 , past valve  70 , through the portion of discharge conduit  50  downstream from valve  70  and ultimately to collection station CT. Upon completion of the discharge of sewage from tank  30  through the discharge conduit  50 , valve  70  is automatically closed and the vacuum sewage transport system of the invention is restored to the standby condition. 
     Controller  80  ( FIGS. 2A  and B) is mounted on valve  70  by one or more brackets  100  or other suitable means. Controller  80  includes a housing  81  formed from an assembly of generally cylindrical and axially aligned sections  110 ,  120 ,  120 A,  130 ,  140  and  150 . The sections may be secured together by a series of bolts or other fasteners (not shown). Seals S are located between adjacent sections. 
     A pressure sensor conduit  43  is disposed in pressure communication with pipe  40  at one of its ends and, at its opposite end, is coupled to a pressure sensor port  111  of section  110 . Port  111  opens into a first chamber  113  which is defined by a wall  114  of section  110  and a flexible diaphragm  160 . A second chamber  121  is located on the opposite side of diaphragm  160  and is formed by diaphragm  160  and a wall  122  of section  120 A. Chamber  121  is normally vented to atmosphere through a port  123  ( FIGS. 3 and 3A ). A port  124  extends through wall  122  providing an air flow path between chambers  121  and  125  ( FIG. 3B ). 
     A valve and actuator assembly  170  ( FIGS. 3 and 3B ) is located in second chamber  121  and is used to selectively allow flow between chambers  121  and  125 . Valve and actuator assembly  170  includes a sealing member  171 , an actuating lever  172 , a seal seat  173 , a biasing means  174  and a retainer  175 . In the embodiment shown, biasing means  174  is a spring. Sealing member  171  in the embodiment shown includes a head portion of  171 A with a shaft  171 B extending from a rounded surface  171 D. An opening  171 C extends through the free end of shaft  171 B. Lever  172  includes a first end  172 A and a second end  172 B. Seal seat  173  is positioned in port  124 . Sealing member  171  and lever  172  are located in chamber  121  on one side of wall  122 . Shaft  171 B extends through seal seat  173 . Note that rounded surface  171 D of sealing member  171  is self-centering on seal seat  173 . Biasing means  174  is positioned on the opposite side of wall  122  and is positioned around shaft  171 B. Shaft  171 B extends through retainer  175  and is secured in place by inserting pin  175 A through opening  171 C in shaft  171 B. 
     A third chamber  125  is formed by wall  122  and a diaphragm  161 . A port  126  ( FIGS. 3 and 3C ) extends between sections  120 A and  120  of controller  80  and communicates with chamber  125 . 
     A fourth chamber  127  is formed by diaphragm  161  and a wall  131  of section  130 . A generally cylindrical rod  180  abuts and extends laterally from diaphragm  161 , through an opening  181  in wall  131  and through a seal  182  positioned in opening  181  to prevent fluid or pressure leakage from chamber  127 . A biasing means  183  (which is a spring in the embodiment shown) is located between diaphragm  161  and a wall  131  to maintain diaphragm  161  in the standby position illustrated in  FIG. 3 . 
     A fifth chamber  141  is located on the opposite side of wall  131  from chamber  127  and is formed by wall  131  and a wall  142  of section  140 . A vacuum port  143  extends from section  140  and connects to a vacuum line that communicates with the vacuum side of discharge conduit  50  through check valve  500  as described in greater detail below. Tapered rod  184  extends from rod  180  opposite diaphragm  161 . In the standby position illustrated in  FIG. 3 , all of tapered rod  184  is located in chamber  141  to preclude leakage of vacuum or low pressure therefrom. 
     A sixth chamber  151  is defined by wall  142  and wall  152  of section  150 . An atmospheric pressure port  153  extends from wall  152  and is in communication with chamber  151 . A valve connection port  154  also extends from section  150 . 
     A sealing member  185  ( FIGS. 3 and 3D ) having a first sealing side  185 A and a second sealing side  185 B is secured to one end of shaft  184 . A first valve seat  186 A is located in an opening  142 A in wall  142  through which shaft  184  extends. A second valve seat  186 B is located adjacent the opening to port  153 . When the controller is in the standby condition of  FIGS. 3 and 3D , side  185 A of sealing member  185  engages valve seat  186 A to prevent vacuum communication from chamber  141  with chamber  151  and valve connection port  154 . In this position, chamber  151  and valve connection port  154  are under atmospheric pressure as a result of being in communication with atmospheric pressure port  153 . 
     Port  123  is in communication with port  153  through a flow path  123 A and two ports  123 B ( FIG. 3 ). An air filter  123 C and a duck bill valve  123 D ( FIGS. 3 and 3E ) are located in flow path  123 A between port  123  and port  123 B. Note that duck bill valve  123 D includes a port  123 E through which air at atmospheric pressure can flow even when orifice  123 D is closed as shown in  FIGS. 3 and 3E . 
     The speed of air flow through and pressure equalization between chambers  121 ,  125 ,  127  and  141  is controlled by port  126  and a series of orifices, valves and chambers. Chamber  125  is in communication with chamber  126 A through port  126  and adjustable orifice  200  ( FIGS. 3 and 4 ). Adjustable orifice  200  includes notched member  201  having a plurality of orifices  202  of varying sizes extending therethrough. Member  201  is mounted on a rotatable shaft  201 A in section  120  adjacent wall  122 . A portion  203  of section  120  retains member  201  in controller  80 . A lever  201 B may be used to rotate member  201  to align the orifice  202  of the desired size such that it is in communication with port  126  as shown in  FIGS. 4 and 5 . A detent member DM is provided adjacent member  201 . In one embodiment, detent member DM is a compressible member, that locates within successive recesses of notched member  201  as it is rotated, thereby indicating alignment of successive orifices  202  with port  126 . 
     Chamber  126 A can communicate with chambers  127  and  141  through orifices  300 A and B and check valve  400  ( FIGS. 3 and 6 ). Check valve  400  is in the open position when controller  80  is in the standby state. This serves, through vacuum port  143 , ports  126  and orifices  200 ,  300 A and  300 B, to maintain equalized pressure in chambers  125 ,  127  and  141  at the low or vacuum pressure of the section of conduit  50  downstream from valve  70  during standby. Fluid communication between chambers  125 ,  127  and  141  is achieved and controlled by this series of ports, orifices and valves, as described in greater detail below. 
     Vacuum is supplied to controller  80  through a vacuum line  143 A, which is connected to at one end to vacuum port  143  in a manner known in the art, such as the one disclosed in U.S. Pat. No. 4,171,853, and at the opposite end to check valve  500 . Vacuum line  143 A communicates through check valve  500  with the section of discharge conduit  50  downstream from valve  70  and thereby supplies a constant low pressure or vacuum source to the controller through vacuum line  143 A and vacuum port  143 . In the standby state, chamber  151  is maintained at atmospheric pressure through an air breather (not shown) which communicates with port  153  in a manner known in the art. The controller communicates with the valve  70  through valve connector port  154 , which is in pressure communication with the upper end  71  of valve  70 . 
       FIG. 8  is an exploded perspective view of check valve  500  according to one embodiment of the present invention. Check valve  500  generally includes a main body  510 , a retaining member  520 , a sealing element  530 , and a cover  540 . 
     Referring to  FIGS. 8, 11 and 12 , main body  510  in the embodiment shown includes a post  511  having a first end  512  and a second end  513 . First end  512  includes threads  512 A. Threads  512 A engage corresponding threads in a threaded opening (not shown) in valve  70  to secure main body  510  to valve  70 . Post  511  has an interior passageway  514  extending from first end to  512  and second end  513 . Main body  510  further includes a housing  515  having an interior chamber  516 , a closed end  517 , and an open end  518 . Chamber  516  is in fluid communication with passageway  514  of post  511  and includes a lower surface or floor  516 A, a first sealing surface  516 B, and a second sealing surface  516 C. Open end  518  has a circumferential flange  518 A having an enlarged or protruding section  518 B. Housing  515  is disposed relative to post  511  such that floor  516 A of chamber  516  angles downwardly toward interior passageway  514  of post  511 . Housing  515  further includes a peripheral groove  518 C positioned between closed end  517  and open end  518 . Housing  515  also includes an electronic air admission controller (EAAC) port  519 A and a monitor connector  519 B. Port  519 A can be used to connect an EAAC of types known in the art to check valve  500 . The EAAC can be used to selectively introduce air into vacuum sewage system  10  as is known in the art. Connector  519 B can be used to connect monitoring equipment to check valve  500  to obtain data and report the operating condition of vacuum sewage system  10 . 
     Retaining member  520  is a substantially annular member having a first end  521 , a second end  522  and an opening  523 . First end  521  has an enlarged section or protrusion  524  and second end  522  also has an enlarged section or protrusion  525 . Retaining member  520  is a flexible or compressible resilient member. Force may be applied to first end  521  and/or second end  522  to move first end  521  and second end  522  closer together or farther apart, thereby increasing or decreasing the size of opening  523 . When the force is removed, first end  521  and second end  522  return to the positions shown in  FIG. 8 , thereby restoring the size of opening  523  to that shown in  FIG. 8 . 
     Sealing member  530  is a disk-like member having a front face  531 , a first section or flange  532 , a second section  533  extending from first section  532 , a third section  534  extending from second section  533 , a curved or undulating section  535  connected to third section  534 , and a central or sealing section  536  connected to curved section  535 . Sealing surface  536  has a sealing surface  536 A. Curved section  535  includes a plurality of openings  537  spaced around central or sealing section  536 . Peripheral wall  532  includes an enlarged or protruding section  532 A. Sealing member  530  is constructed from a resilient and flexible material suitable for performing the functions described herein. For example, sealing member  530  may be constructed from rubber. 
     Cover  540  in the embodiment shown has an open end  541 , a peripheral side wall  542  and a front wall  543 . Side wall  542  has a beveled edge  544  and an inner surface  545 . Side wall  542  and front wall  543  are arranged so as to form an interior chamber  546  in cover  540 . The periphery of wall  542  is configured so as to have an enlarged or protruding section  542 A. Front wall  543  includes a central section  547  having a sealing surface  547 A. A seal S is positioned on front wall  543  spaced apart from and around central section  547 . A connector  548  extends from central section  547  of cover  540 . Connector  548  has a passageway  548 A in fluid communication with interior chamber  546  of cover  540 . Cover  540  further includes an interior recess or groove  549  for receiving flange  518 A of main body  510  as described below. 
     To assemble check valve  500 , retaining member  520  is positioned in groove  518 C of housing  515 . Sealing member  530  is inserted in chamber  516  of housing  515  such that second section  533  of sealing member  530  contacts first sealing surface  516 B of chamber  516  and third section  534  of sealing member  530  is adjacent second sealing surface  516 C of chamber  516 . Note that in order to insert sealing member  530  into chamber  516 , sealing member  530  must be oriented such that protruding section  532 A is aligned with protruding section  518 B of flange  518 . In this manner, sealing member  530  can only be inserted into chamber  516  in one orientation. Protruding section  532 A nests within protruding section  518 B when sealing member  530  is inserted in chamber  516 . After sealing member  530  is inserted in chamber  516 , cover  540  is slid over flange  518  of housing  515  such that flange  518  is positioned with groove  549  and second section  533  of sealing member  530  is positioned between first sealing surface  516 B of chamber  516  and front wall  543  of cover  540  as shown in  FIGS. 11 and 12 . As cover  540  is slid toward housing  515 , beveled edge  544  of cover  540  contacts enlarged sections  524  and  525  of first end  521  and second end  522 , thereby compressing retaining member  520  inward toward groove  518 C. When enlarged sections  524  and  525  clear beveled edge  524 , they exert force outwardly on inner surface  545  of side wall  542  to secure cover  540  to main body  510 . Note that in order to secure cover  540  to housing  515 , cover  540  must be oriented such that protruding section  542 A is aligned with protruding section  518 B of flange  518  and with protruding section  532 A of sealing member  530 . In this manner, cover  540  can only be positioned on housing  515  in one orientation, with protruding section  518 B nested within protruding section  542 A of cover  540 . 
     When check valve  500  is assembled as shown in  FIGS. 11 and 12 , seal S is clamped between front face  531  of sealing member  530  and front wall  543  of cover  540 . Sealing member  530  is clamped in place around its entire periphery via the positioning of second section  533  of sealing member  530  between first sealing surface  516 B of chamber  516  and front wall  543  of cover  540 . Securing sealing member  530  within chamber  516  in this manner helps prevent undesirable distortion of sealing member  530  under pressure surges that can occur during operation by providing a greater area of support to sealing member  530  as compared to other check valve configurations, such as ones that utilize a sealing member centrally mounted on a post. The curved or undulating shape of curved section  535  of sealing member  530  also resists undesirable distortion and results in a check valve having a low cracking pressure. As used in this disclosure, “low cracking pressure” as applied to check valve  500  is a cracking pressure that does not cause a reduction of the vacuum supply to controller  80  that would prevent controller  80  from actuating at the desired vacuum level. In certain embodiments of the invention, a low cracking pressure is one that does not prevent actuation of controller  80  at a vacuum pressure of 5 inches of mercury. In certain embodiments of the invention, a low cracking pressure is less than 1 inch of mercury vacuum. 
     Check valve  500  is secured to valve  70  by threading first end  512  of post  511  into a corresponding threaded opening on valve  70 . Vacuum line  143 A is connected at one end to connector  548  of cover  540  and at the opposite end to vacuum port  143  of controller  80 . 
       FIG. 11  illustrates check valve  500  in the standby state, i.e., the state of check valve  500  when controller  80  is in the standby state shown in  FIG. 3 . In this state, sealing surface  536 A of sealing member  530  is in contact with sealing surface  547 A of cover  540 , and an annular space AS is formed between curved section  535  of sealing member  530  and front wall  543  of cover  540 . In the standby state, check valve  500  holds the existing vacuum in controller  80  and prevents reverse flow of liquid and debris into controller  80 . 
     Note that check valve  500  includes a number of features designed to remove moisture and debris from check valve  500 . Openings  537  in sealing member  530  are larger than the smallest cross-section of passageway  548 A of connector  548 . Thus, any debris that is large enough to pass through passageway  548 A can also pass from one side of sealing member  530  to the opposite side through openings  537 . The smallest cross-section of passageway  514  of post  511  is also larger than the smallest cross-section of passageway  548 A. Thus, any debris that can pass through passageway  548 A can also pass through passageway  514  and out of check valve  500 . Moisture can also flow from one side of sealing member  530 , through openings  537 , to the opposite side of sealing member  530 , and out of check valve  500  via passageway  514 . Second, disposing floor  516 A of chamber  516  at a downward angle to passageway  514  assists in draining moisture and debris out of chamber  516  via passageway  514 . Removing moisture from check valve  500  is desirable in certain operating conditions, such as cold weather environments in which moisture that accumulates in check valve  500  can freeze and interfere with operation of check valve  500 . 
     In certain embodiments of the invention, openings  537  and passageway  514  are designed such that they do not restrict the flow of air through controller  80 , which could result in controller  80  not actuating or operating as desired. Accordingly, in certain embodiments of the invention, the rate of air flow through check valve  500  is greater than the rate of air flow through controller  80 . In certain embodiments of the invention, this higher flow rate through check valve  500  is achieved by making openings  537  and the smallest cross-section of passageway  514  larger than the largest cross-section of the various ports and air flow paths of controller  80 , such as port  123 , flow path  123 A, ports  123 B, orifice  123 D, port  123 E, port  124 , port  126 , opening  142 A, vacuum port  143 , vacuum line  143 A, atmospheric pressure port  153 , valve connection port  154 , adjustable orifice  200 , orifices  202 , orifice  300 A, orifice  300 B, and check valve  400 . 
     In operation, controller  80  begins in the standby state illustrated in  FIG. 3 . In this state, head portion  171 A of sealing member  171  is seated on seal seat  173  by the force of biasing means  174  and the pressure differential between chambers  121  (which is at atmospheric pressure) and chamber  125  (which is at low or vacuum pressure). Check valve  500  is also in the standby state shown in  FIG. 11 . 
     Sewage accumulation in tank  30  produces pressure in pipe  40 , which is communicated to chamber  113  through pressure sensor port  111  through conduit  43 . This pressure increase urges diaphragm  160  toward wall  122  as shown in  FIG. 7 . As diaphragm  160  moves toward wall  122 , it applies pressure to first end  172 A of lever  172 . This in turn causes first end  172 A to move toward wall  122  and second end  172 B to pivot away from wall  122 . As second end  172 B pivots away from wall  122 , it draws head portion  171 A of sealing member  171  away from sealing seat  173  against the biasing force of biasing means  174 , as illustrated in  FIG. 7A . This establishes fluid and atmospheric pressure communication between chambers  121  and  125  as atmospheric air flows from port  153 , through flow path  123 A and through port  123  into chamber  121  and through port  124 . Note that the flow of air causes duck bill valve  123 D to open as shown in  FIG. 7B . Alternatively, if check valve  600  is used, the flow of air through passageways  604  and opening  150 A will cause flange  603  to unseat from section  150  to permit increased air flow. 
     As the low or vacuum pressure in chamber  125  is increased by the introduction of air at atmospheric pressure, diaphragm  161  is urged toward wall  131  by the combination of the increased pressure in chamber  125  and the low or vacuum pressure in chamber  127 . This causes rod  180  and tapered rod  184  to move toward wall  152 . As this occurs, first sealing side  185 A of sealing member  185  disengages valve seat  186 A and second sealing side  185 B seats against valve seat  186 B, thereby closing atmospheric air port  153  against further communication of atmospheric air into chamber  151  and valve connector port  154 . As first sealing side  185 A moves away from valve seat  186 A, fluid and pressure communication between chambers  141  and  151  is established as air flows around sealing member  155  and tapered post  184 . This exposes chamber  151  to low or vacuum pressure from vacuum port  143 . This also increases the pressure in chamber  141  and causes air flow through vacuum port  143  toward check valve  500 , which causes sealing surface  536 A of sealing member  530  to move away from and to become spaced apart from sealing surface  547 A of cover  540  as shown in  FIG. 12 . 
     As the atmospheric pressure communicating with valve  70  through valve connector port  154  is decreased under the influence of vacuum pressure from chamber  141 , valve  70  is activated in a manner known in the art, such as the manner described in U.S. Pat. No. 4,179,371. As valve  70  is opened, the upstream portion of discharge conduit  50  is placed under low or vacuum pressure. Since tank  30  is essentially at atmospheric pressure, the low or vacuum pressure in discharge conduit  50  causes the sewage to be discharged into discharge conduit  50  and transported to collection station CT. 
     The discharge of sewage from tank  30  produces an almost immediate drop of pressure in communication with diaphragm  160  through pipe  40 , thereby reducing the pressure in chamber  113 . This draws diaphragm  160  away from wall  122  and first end  172 A of lever  172 . As a result, head portion  171 A of sealing member  171  is urged against sealing seat  173  under the influence of biasing means  174 , thereby preventing flow from chamber  121  to chamber  125  through port  124 . This causes the vacuum in chambers  141  and  151  to drop, resulting in the closure of check valve  400  as the pressure in chambers  125  and  127  begins to equalize. The rate of equalization is controlled by the size of orifices  200 ,  300 A and  300 B and by the size of chamber  126 A. For example, the smaller the orifices, the slower the equalization of pressure between the various chambers. Similarly, the larger the volume of chamber  126 A, the longer the equalization time between the various chambers, as the larger reservoirs have greater volume that needs to be equalized. Use of larger volumes permits use of larger orifices, which in turn allows moisture to pass through controller  80  before the system vacuum is depleted. This also eliminates the need for dip tubes. 
     As the differential pressures in chambers  125  and  127  equalize, the diaphragm  161  moves toward wall  122  and draws first sealing side  185 A back against valve seat  186 A. This opens atmospheric air port  153 . Atmospheric air pressure again communicates through valve connector port  154  and the resulting pressure change closes valve  70 . The movement of sealing member  185  also prevents low or vacuum pressure from being transmitted from chamber  141  to chamber  151 . When this occurs, check valve  400  resumes its normally open condition and pressure across chambers  125 ,  127  and  141  is equalized to that of the vacuum line pressure of conduit  50 . 
     As controller  80  returns to the standby state, check valve  500  also returns to the standby state of  FIG. 11 . Up until the time at which sealing surface  536 A of sealing member  530  contacts sealing surface  547 A of cover  540 , vacuum is supplied to controller  80  through passageway  514  of post  511 , chamber  516  of housing  515 , openings  537  of sealing member  530 , passageway  548 A of connector  548 , vacuum line  143 A, and vacuum port  143 . 
     As noted above, backpressure can sometime occur during operation of vacuum sewage system  10 . This backpressure can force sewage from discharge conduit  50  into controller  80  via vacuum port  143 . However, in vacuum sewage systems according to the present invention, backpressure through passageway  514  and chamber  516  will force central section  536  of sealing member  530  toward central section  547  of front wall  543  of cover  540  so that sealing surface  536 A of sealing member  530  seals against sealing surface  547 A as shown in  FIG. 11 , thereby closing off access to passageway  548 A of connector  548  and preventing sewage from entering controller  80 . Sewage and moisture that may have accumulated in annular space AS under such backpressure conditions can drain through openings  537  and out of check valve  500 . 
     As noted above, vacuum pumps VP are cycled on and off to maintain the appropriate level of vacuum in the vacuum sewage system, including in controller  80 . Check valve  500  will be activated if vacuum pumps VP cycle on while check valve  500  is in the standby state. Specifically, activation of vacuum pumps VP when check valve  500  is in the standby state will cause sealing member  530  to move toward closed end  517  of main body  510 , which moves sealing surface  536 A of sealing member  530  away from sealing surface  547 A of cover  540  as shown in  FIG. 12 . With sealing member  530  in this position, vacuum is supplied to controller  80  through passageway  514  of post  511 , chamber  516  of housing  515 , openings  537  of sealing member  530 , passageway  548 A of connector  548 , vacuum line  143 A, and vacuum port  143 . Check valve  50  will return to the standby state of  FIG. 11  after vacuum pumps VP cycle off. 
     Although the present invention has been shown and described in detail the same is by way of example only and is not a limitation on the scope of the present invention. Numerous modifications can be made to the embodiments shown and described without departing from the scope of the present invention. For example, although check valve  500  has been described in connection with preventing sewage backflow into controller  80  via vacuum line  143 A, check valve  500  can be utilized in other locations in vacuum sewage system  10  where it is desirable to prevent backflow. Retaining member  520  could be eliminated and the remaining components of check valve  500  could be secured together by alternate means, such as by configuring main body  510  and cover  540  such that they interlock or snap-fit together.